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Executive Summary

North Americans have many options when it comes to heating and cooling their homes. Most can choose from several locally available fuels, and then select from a

variety of equipment to convert the fuel into heat. Although not all homeowners thoroughly research their heating options, they all want a system that delivers comfort, reliability, and fuel efficiency. When it comes to meeting these objectives, nothing matches a propane-fueled heat source combined with a hydronic distribution system.

This publication discusses the synergistic combination of propane and hydronics technology in detail. It begins with an overview of propane as a universal fuel for supplying virtually any heating need in or around a home. These needs include space heating, domestic water heating, cooking, clothes drying, patio heating, and grilling. Beyond these tasks, propane can power emergency generators, repel mosquitoes, operate outdoor lighting, provide a cozy fireplace, and even power equipment that cools buildings in warm weather. Given all these possible uses propane truly is exception energy.

But a fuel source is only part of an overall heating system. Delivering exceptional comfort precisely when and where it’s needed requires a superior heat distribution method, and that’s where modern hydronics technology comes in.

Hydronic heating systems use water as a “conveyor belt for heat.” Heat is loaded onto a stream of flowing water within a propane-fueled heat source such as a boiler or water heater. This heat is carried throughout the building as the water flows along a distribution system containing tubing, circulators, and other components. Finally, the heat is unloaded from the water and released into individual rooms using one of several types of heat emitters.

The somewhat cooler water then returns to the heat source to repeat the cycle.

Properly installed hydronic systems provide superior comfort in every room of a house or commercial building. In some systems this comfort is delivered by gently warmed room surfaces such as floors, walls, or ceilings. Such systems have no visible heating hardware within the rooms and thus do not compromise the aesthetics or furniture placement within those rooms. This approach is called hydronic radiant panel heating, and it’s extensively described in this publication. Other heat emitters to be discussed included fin-tube baseboard, panel radiators, and air handlers. Some systems may even combine two or more types of heat emitters to perfectly match the aesthetic, occupancy, and budget constraints of the owners.

Propane-fueled hydronic systems can also provide an endless supply of domestic hot water using the same heat source that warms the building. Such systems can even be extended to melt snow from steps and walkways, or heat a swimming pool. The essence of a modern hydronic heating is a single heat source supplying heat to several loads in and around the building. This approach lowers installation cost, reduces service requirements, and increases fuel efficiency compared to installing separate heat sources for each heating requirement. It’s also a perfect complement to other domestic uses of propane.

After reading this publication we hope you agree that the combination of propane and modern hydronics technology offers unmatched versatility and comfort. Section 10 provides a listing of references and websites that can be used to further study of the topics we’re about to discuss.

Enjoy.

Hydronics and PropaneExceptional Comfort – Exceptional Energy

Table of Contents

Executive Summary

Section 1: Propane, Exceptional Energy

Section 2: What is Hydronic Heating?

Section 3: The Advantages of Hydronic Heating

Section 4: The Basic Components of a Hydronic System

Section 5: Propane-Fueled Heat Sources

Section 6: Heat Emitter Options

Section 7: Other Loads Supplied by Hydronics

Section 8: Case Studies

Section 9: Cooling Options for Use with Hydronic Heating

Section 10: Additional Sources of Information

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Section 1: Propane, Exceptional Energy

This publication discusses how propane, in combination with water-based “hydronic” heating hardware, can deliver superior comfort, low fuel bills, and reliable

operation over many years. However, this specialized topic is only part of the story propane has to tell. Before discussing it in detail lets look at the big picture.

Simply stated…

No other fuel offers the versatility, economy, environmental benefits, and convenience of propane!

Here’s a quick look at each of these benefits.

Propane is Versatile Almost any heating requirement in a modern house or commercial building can be supplied by propane. These requirements include:

Space heatingHeat derived from propane can be delivered to buildings in many ways. These include central forced-air furnaces and water-based hydronic heating systems (the principle subject of this publication). Other propane-fueled devices that provide heat include overhead infrared heaters, unit heaters, through-the-wall console heaters and propane fireplaces. Two or more of these methods can easily be combined where they make the most sense in a given project. All can be supplied by a modern, safe, and easily installed propane distribution system.

Domestic water heatingVirtually unlimited amounts of domestic hot water can be supplied through properly-sized propane water heaters. These include standard tank-type water heaters, as well as increasingly popular “tankless” water heaters. It also includes “indirectly-fired” water heaters that are used in combination with hydronic space heating.

Ranges and OvensAsk a professional chef if they prefer gas- or electric ovens and cooktops. It’s a virtual certainty they’ll tell you a gas cooking appliance is their first choice. Propane cooking appliances respond faster than electric appliances and can deliver greater heat output when needed. With more and more homeowners opting for high performance (commercial grade) cooktops and ovens, propane is ready to ensure their culinary pursuits will be sizzling successes.

Outdoor grillsAmericans love their outdoor grills, and more than 63 percent of those grills are fueled by propane. In homes with a central propane supply system outdoor grills are ready to operate year round. There’s no need to periodically change the propane tank.

HearthsWho doesn’t enjoy relaxing in front of a warm hearth on a cold winter evening? When fueled by propane, that fireplace is ready to fire any time of the day or night. Enjoy the warm, efficient, radiant heat without the mess, smoke, or residue created by wood fires. Extend this enjoyment from inside to outside with a propane fireplace or fire pit on the deck or patio. It’s safe, clean, smokeless, and ready to go whenever you want it.

Clothes DryersElectrically operated clothes dryers can be one of the most inefficient appliances to operate. At the same time they may not always completely dry clothes, especially when people are rushed. As is the case with cooktops, propane dryers have higher rates of heat input and thus dry clothes faster. They can also cost significantly less to operate than do electric clothes dryers.

Patio HeatersWant to enjoy your outdoor patio on a cool spring evening? Consider a propane infrared radiant heater. Such devices provide radiant comfort up to twenty feet away while operating in virtual silence and without smelly emissions.

Pool Heating How many pool owners, especially those living in northern climates, look at the inviting water knowing it’s often too cold for an enjoyable swim? How many times does cool water stop them from enjoying the pool they’ve spent thousands of dollars to install?

It doesn’t have to be that way. A propane pool heater can raise the temperature of a pool to a very comfortable level and ensure it stays there. Swimming seasons can easily be extended one or two months in Northern climates, and even maintained year round in warmer locations. It’s even possible to heat the pool using the same propane boiler that heats the house in winter. Section 7 of the publication shows you how to do this.

Propane fireplaces are ready whenever you are.Source: PERC

Figure 1-1

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Other Uses for Propane Most people associate propane with heating. The previous discussion certainly confirms its many uses in this category. However, there are several other (non-heating) domestic uses for propane that you may not know about. They include:

Emergency generatorsFew of us enjoy spending several hours, or worse, several days, in a home without electricity. Did you know that propane-fueled electrical generators are available as an option to conventional gasoline-fueled generators? These modern devices can turn on automatically within a few seconds of a power outage, and provide stable and safe electric power to a home until utility-supplied electricity is restored. Located outside, these devices are quieter than gasoline- or diesel-powered generators, and operate without the smoke and emissions that some other generators produce.

Outdoor lighting Before electricity, many streetlights were operated by gas. Propane-fueled outdoor lighting is still available in both wall-mounted and post mounted fixtures. The light emitted combines old style charm with energy efficiency. Even better, this lighting requires no electricity and thus can operate in a power outage. Some gas lights can even be adapted to an on/off switch just like electric lights.

Mosquito EliminatorsPart of enjoying an outdoor patio with a grill, lighting, and heating is not sharing that space with mosquitoes. Propane mosquito eliminators generate non-toxic compounds that act like a magnet for mosquitoes, drawing them away from patio areas and trapping them in the device.

MicroCHP SystemsImagine a propane-fueled device that produces both heat and electricity. Such “cogeneration” devices have existed for several decades, but only for large industrial applications. However, new technology allows the concept to be scaled down for residential and light commercial buildings. MicroCHP (Combined Heat and Power) units consist of a small internal combustion engine fueled by propane that turns the shaft of an electric generator. Heat produced by the engine is collected through a liquid cooling system and can be used to heat a building or domestic water. Modern engineering allows such devices to operate with very low noise levels. Low enough that they can be installed in a residence just like a furnace or boiler.

Chilled Water CoolingAlthough it may seem counterintuitive, it’s possible to economically produce chilled water for building cooling by burning propane. The process is called absorption cooling, and it has been used for several decades in larger commercial buildings. Small absorption cooling units are now available for cooling residential and light commercial buildings. They’re discussed in more detail in section 9.

Propane is EconomicalHigh performance condensing boilers and furnaces convert propane to heat at efficiencies significantly higher than those of current-generation oil-fired equipment. Higher efficiency means lower fuel cost.

Propane-fueled emergency generatorSource: Generac Power Systems,Inc.

Figure 1-2

Propane-fuel CHP unit produces both heat and electricitySource: Marathon Engine Systems

Figure 1-3

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But fuel cost is only part of the total operating cost of any heating system. For example, propane-fueled boilers and furnaces typically require less maintenance than do boilers and furnaces fired by fuel oil. They do not require the annual replacement of fuel filters and burner nozzles.

Most modern propane-fueled boilers and furnaces can also be vented through exterior building walls thus eliminating the cost of installing and maintaining a chimney. The installed cost of a conventional chimney, even in a new home, can easily exceed $2,500.

The use of propane rather than utility-supplied natural gas eliminates the monthly service charge associated with having a gas meter on the premises. Such charges are added to every month’s utility invoice, and often exceed $200 per year. This adds up to thousands of dollars over the life of the system.

Propane is Environmentally FriendlyPropane is one of the lightest, simplest hydrocarbons in existence. This makes it one of the cleanest burning of all fossil fuels. The on-site emissions associated with burning propane have lower carbon content than gasoline, diesel, fuel oil, and ethanol.

A significant percentage of the electricity supplied in the United States is generated by coal-burning power plants. Burning a pound of coal releases more than twice the amount of carbon dioxide as does burning a pound of propane. By using propane rather than electricity, consumers can reduce emissions and help preserve the environment.

According to the federal Environmental Protection Agency, much of the sulfur dioxide in the atmosphere, which produces acid rain, comes from coal-fired power plants. In contrast, the production and combustion of propane produces very little of the compounds responsible for acid rain.

Propane gas is nontoxic as well as insoluble in water. If a leak in a propane tank or supply system should ever occur, the propane vaporizes and

dissipates into the air. It will not create dangerous floor puddles as will other liquid fuels.

Approximately 90 percent of the propane used in the United States is produced in the United States. This reduces dependence on foreign energy suppliers as well as the transportation energy required to import foreign fuel.

Propane is ConvenientGiven all the uses for propane, you may be wondering how it’s supplied to all the potential appliances. The answer is a modern underground storage tank connected to a distribution piping system within the building.

Underground storage tanks are quickly and easily installed by propane professionals. Excavation depths of 5 feet are usually sufficient to bury a propane tank. Only the small service dome at the top of the tank is visible above ground, and can easily be integrated with landscaping so that it’s virtually unnoticed. Underground storage tanks for propane range in size from 100 to 2000 gallons. A 500-gallon tank is usually sufficient to supply the needs of a four-bedroom home.

These tanks are not subject to the stringent inspections imposed on underground tanks storing fuel oil, gasoline, or other fuels. To

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0Natural

Gas

52.8

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62.7

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MotorGasoline

70.5

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70.7

kg CO2 per MMBtuSources: DOE 1994, EPA 2007

DistillateFuel

(Diesel)

72.5

ResidualFuel (Heavy

Fuel Oil)

78.6

BituminousCoal

92.7

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186.8

Figure 1-4

A modern propane storage tank being installed undergroundSource: PERC

Figure 1-5

On-Site Emissions for Various Fuels

Emissions of propane relative to other fuelsSource: PERC

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find out more about propane and underground propane tanks go to www.ces.pratt.edu and take a free on line course.

A single buried pipe routes propane to the building. From there it can be divided into individually controlled branches serving each propane appliance. Modern flexible stainless steel tubing can be installed faster than traditional threaded iron pipe, and with far fewer joints. A central propane distribution manifold can supply several branch supply tubes, each one sized for the appliance it serves.

SummaryAs you can see, propane truly is exceptional energy. The sections that follow show you one of the most unique ways to apply this energy in systems that supply a wide range of heating and cooling requirements for buildings. The combination of propane and hydronics technology is both complementary and synergistic. Together they’re a combination that’s hard to beat.

Propane can be easily distributed to several appliances within a home using modern flexible CSST piping.Source: Gastite

Figure 1-6

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Section 2: What is Hydronic Heating?

The best way to describe a hydronic heating system is as “a conveyor belt for heat.” This heat is loaded on at the heat source, carried to where it’s needed by water

moving through the piping, and then unloaded at one or more heat emitters as shown in figure 2-1. Within this concept are thousands of options that allow hydronic heating systems to be specifically tailored to the needs of the building and its owner.

When water absorbs heat inside the heat source, its temperature increases. It doesn’t change from a liquid to a vapor as in a steam heating system. In fact, good hydronic system design prevents liquid water from changing to a vapor at any point in the system.

As water travels through the distribution system, a small portion of the heat it carries is released from the piping and other components. When the water passes through a heat emitter more of the heat is released. The rate at which heat moves from the heat emitter into the room depends on several things, including the temperature of the water as well as that of the room, the size of the heat emitter, and the water flow rate.

The vast majority of residential and light commercial hydronic heating systems are classified as closed-loop systems. The water they contain is sealed in and under slight pressure. Ideally, the same water recirculates through the system over and over, year after year. Very small quantities of fresh water are added only when necessary. This minimizes the potential for corrosion and allows the system to last for decades.

Some hydronic heating systems are as simple as a water heater connected to a loop of flexible plastic tubing that warms a bathroom floor. Others may use multiple boilers and a wide assortment of heat emitters specifically selected to match the

thermal, aesthetic, and budget constraints of a particular building. Those same boiler(s) may also provide the building’s domestic hot water, heat the swimming pool, and even melt snow as it falls on the driveway. The versatility of hydronic systems makes such options available in both new construction and building retrofitting.

When properly planned and installed, modern hydronic heating can provide years of unsurpassed comfort in nearly all types of homes as well as commercial buildings — comfort so good you’ll literally forget its winter as you walk in the door.

boiler

circulator

heat emitter

water flow

propane

heat emitter

heat released

“A hydronic heating system is a conveyor belt for heat.”

Figure 2-1

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Section 3: The Advantages of Hydronic Heating

There are many unique benefits associated with using a propane-fueled heat source in combination with a hydronic distribution system. Any one of them might

be the “key” reason for a prospective customer to choose this unique combination of fuel and heat delivery method. This section describes and illustrates a synergistic collection of benefits that is unrivaled by other heating options.

Superior comfortHydronic heating has long enjoyed a well-deserved reputation for providing excellent thermal comfort. Some hydronic systems provide this comfort by warming the surfaces within a room as well as the room’s air. Such systems address the fact that providing true thermal comfort involves more than simply maintaining a room at a given air temperature. They release heat into spaces in harmony and balance with human physiological needs. Although it may not be apparent where the heat is coming from it will be obvious that the comfort is far superior to that provided by other systems.

Unobtrusive installation: Another significant advantage of hydronic heating is the ability to install it without having to drill, saw, or otherwise hack out major pieces of the building’s structure.

This benefit is a direct result of the physical properties of water. A given amount of water can absorb almost 3,500 times more heat than the same amount of air. This implies that a hydronic system only has to move about 1/3500 as much volume as does a forced-air system of equal heating capacity. This drastically reduced volume requirement allows small flexible tubing to replace large cumbersome ducting.

Consider the ducting installation shown in figure 3-2. Beyond their unsightly appearance, such ducts reduce headroom and likely prevent the ceiling from being finished. They also are subject to sagging or damage over time.

In contrast, the small flexible tubing shown in figure 3-3 is easily routed through floor framing. This type of tubing is ideal for new construction as well as retrofit applications where access to building framing cavities is more difficult.

Here’s another way to put the difference between hydronic tubing and forced-air ducting in perspective. A 3/4-inch diameter tube can deliver the same amount of heat as an 8-inch high by 14-inch wide duct when both systems are operated under typical conditions. This contrast is shown in figure 3-4.

Ducting often compromises headroom in basements.

Barefoot-friendly floors on the coldest day of winter

Figure 3-1

Figure 3-2

Small, flexible, hydronic tubing routed through floor framing

Figure 3-3

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When necessary, a 3/4” tube is easily routed through the home’s floor framing without having to drill large holes that could weaken the structure. In many situations the entire hydronic distribution system can be easily concealed within the home’s structure.

Accommodating an 8-inch x 14-inch duct in a similar situation is a very different matter. With the possible exception of wooden “I-joist” framing, or specially designed floor trusses, a duct this size simply can’t be run laterally through the floor framing. The necessary compromise is often to suspend the ducting from the bottom of floor framing as shown in figure 3-2, or conceal the ducting by building valences or soffits around it within living spaces.

Why should the aesthetics of an otherwise meticulously planned building be compromised to “shoe-horn” in the heating system?

Aesthetic issues aside, there are countless buildings in North America where poor comfort is the result of a compromised ducting system.

Design FlexibilityHydronic heating offers virtually unlimited ways to accommodate the comfort needs, usage, aesthetic tastes, and budget constraints of any building. In many cases, a single propane-fueled boiler can provide space heating, domestic hot water, as well as specialty requirements such as pool or hot tub heating and melting snow off steps, sidewalks, and driveways as shown in figure 3-5. No other type of heating system offers this much versatility from a single heat source.

Clean OperationOne of the leading complaints from owners of forced-air heating systems is the amount of dust and other airborne pollutants their systems distribute through the house. Although sometimes the result of poorly maintained filters, this complaint demonstrates one of the potential pitfalls of forced-air distribution systems.

Figure 3-6 shows the inside of ducting recently removed from a house. The inside of the ducting is coated with dust, pet hair, and mold spores from years of operation even when a filter was present in the system. The occupants of this house had been breathing air that, in some cases, passed through this ducting several times each hour.

14" x 8" duct

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this cut would destroy the load-carrying

ability of the floor joists

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A 3/4-inch diameter tube carrying water can deliver the same amount of heat as 8-inch by 14-inch duct carrying air.

Hydronic snowmelting keeps this walkway free of ice and snow. Courtesy of Gary Todd

Figure 3-4

Figure 3-5

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In contrast, most hydronic heat emitters induce very gentle, almost imperceptible air circulation. The heat emitters that use small fans or blowers create room air circulation rather than whole-house air circulation. People with allergies or other respiratory conditions are especially appreciative of the reduced air movement afforded by hydronic heating.

Quiet OperationToday’s homes are often thought of as a sanctuary from the noises associated with work and public life. Why should this solace be compromised by a noisy heating system?

A properly installed hydronic system will operate with virtually no detectable sound in the occupied areas of a home. This is especially true for modern propane-fueled boilers, which operate at extremely low noise levels—so low that many people have to place their ear against the boiler to hear any sound at all. Some modern hydronic systems operate with continuous water circulation and variable water temperature to eliminate piping expansion noises.

ZonabilityA heating system that maintains an entire building at the same temperature doesn’t give occupants with individual comfort preferences much choice. The heating system in most homes should divide the building into two or more independently controlled comfort zones. Such systems can reduce energy consumption by maintaining lower air temperatures in unoccupied areas. They also allow the comfort level of rooms to be adjusted to suit individual tastes and activity levels.

Imagine a heating system that automatically adjusts itself as sunlight shines in the windows of some rooms but not others. One that automatically reduces heat output when several people gather in the living room, but still maintains a toasty warm bathroom for another person to shower in. This type of “room-by-room” zoning is easy to accomplish using hydronics without resorting to the complex and costly hardware necessary for zoning forced air systems. Some hydronic systems provide room-by-room comfort control at each heat emitter without need of thermostats and associated wiring. An example of such a product is shown in figure 3-9.

Inside of ducting recently removed from a forced-air heating system

Hydronic heating is especially well suited for those will allergies or other respiratory conditions

Properly designed hydronic heating systems operate with virtually no detectable noise

Non-electric thermostatic radiator valve allows for room-by-room comfort control

Figure 3-6 Figure 3-8

Figure 3-7

Figure 3-9

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Abundant Domestic Hot WaterAlthough most people think of hydronic heating as a method for warming buildings, it also provides a unique and efficient way to provide domestic hot water.

Modern luxury homes, some with six or more bathrooms, can place heavy demands on ordinary tank-type water heaters. In some cases those heaters simply can’t keep pace with the demand, especially when several fixtures are in use simultaneously. The inevitable result is “scheduling” showers or baths in spaced out sequence to avoid running out of hot water. The owners are forced to conform to the ability of the water heater rather than to their own convenience.

Why should owners of such homes, many of whom have spent considerable funds for luxury bathrooms, have to compromise the usage of those fixtures based on limitations in the water heating equipment?

Fortunately, a properly configured propane-fueled boiler system combined with a high capacity indirect water heater can supply such hot water demands indefinitely. Such systems provide the ideal combination of storage and heating capacity to efficiently supply small hot water demands as well as the large demands created when several bathrooms are in simultaneous use. Heat for domestic hot water comes from the same propane-fueled boilers that heat the house, warm the pool, and perhaps even melt snow off the driveway. Special controls allow the system to treat the domestic water heating load as a priority. The result is a system that can always keep pace with the hot water demands of a modern luxury home.

Reduced Operating CostHydronic systems reduce the cost of heating a building in several ways.

For starters, the small tubing used in modern hydronic systems loses far less heat to its surroundings than does a duct of equivalent heating capacity. For example, an 8-inch by 14-inch duct loses about 16 times more heat to its surroundings than does a 3/4-inch copper tube, assuming both operate at the same temperature. This heat

loss is very undesirable in situations where piping or ducting is routed through cool basements, crawl spaces, or attics. Heat loss to such spaces is truly heat lost—heat you paid for, and heat that’s needed elsewhere in the building to maintain comfort.

Even if the tubing and ducting were insulated with the same material, heat loss from the ducting would remain much higher than that of the hydronic tubing. It would also cost more to insulate the ducting because of its greater surface area.

Another way hydronic systems reduce energy use is in the electrical power demand of a circulator relative to that of a blower in a forced-air system such as used with furnaces or heat pumps. With good design it’s possible to supply heat to a 2,500 square foot house with a circulator that consumes 80 watts or less of electrical power at full speed. By comparison, the blower in a geothermal heat pump of equivalent heating capacity could demand over 1600 watts—20 times more electrical power! Assuming each distribution system operated for 3,000 hours a year in an area where the current cost of electricity is $0.10 per kilowatt-hour, the blower would require an additional $456 dollars per year for electricity relative to that required by the small circulator. Over the life of the system this would add up to thousands of dollars in higher operating cost.

Some hydronic systems, especially those that heat floors in rooms with high ceilings, lower energy consumption by reducing the tendency of warm air to rise to the ceiling while cool air pools at floor level. This effect is called air temperature stratification. In addition to creating higher heat loss through the ceiling, it’s just the opposite of what’s needed for true thermal comfort.

Because hydronic floor heating doesn’t overheat room air it discourages air temperature stratification. Air temperatures near the ceiling of tall rooms heated by warm floors are typically lower than air temperature at floor level. This enhances comfort and reduces fuel usage.

Hydronic systems can also supply high-capacity domestic water heating

hydronic systems operate with less electrical power demand than forced-air systems

Figure 3-11

Figure 3-10

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The ability to easily zone a hydronic system provides the ability to maintain unoccupied rooms at reduced temperatures while maintaining comfort in occupied rooms. Reduced air temperatures decrease building heat loss and thus reduce fuel consumption.

Some propane-fueled boilers can operate with efficiencies of 95 percent plus when combined with low temperature hydronic distribution systems. Such boilers extract almost all the available energy in each gallon of propane and pass it to the hydronic distribution system, which delivers it to the building in a way that’s ideally matched to human comfort requirements.

Hydronic heating supplied by a propane-fueled boiler is a combination that’s hard to beat. The sections that follow elaborate on many of the options available with this combination of fuel and delivery system. They will show you what modern hydronic heating hardware looks like and how it’s assembled into a compact, quiet, efficient, and affordable comfort system.

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SECTION 4: The Basic Components of a Hydronic System

Those wanting to design or install quality hydronic heating systems must be committed to ongoing learning. New products and design methods will vie for their attention

as the hydronic heating market grows and more people demand the benefits it offers.

Learning must start with the fundamentals. What are the basics components found in almost every type of hydronic heating system, and what are their functions?

This section gives you a basic understanding of the “building blocks” used in almost every residential and light commercial hydronic system. Later sections will demonstrate the repeated usage of these components in a wide variety of systems.

Figure 4-1 shows the fundamental components of a single circuit hydronic system.

Heat SourceThe starting point in a hydronic system is getting heat into the water. While it might be said that almost any device that heats water is a potential hydronic heat source, some options are clearly more practical than others.

One of the most common and most versatile hydronic heat sources is a propane-fueled boiler. Such boilers are discussed in detail in section 5. Other possible options include geothermal heat pumps, solid fuel boilers, and solar energy systems.

Each of these options has strengths and limitations. Some constrain the system design in terms of operating temperature, or flow rates. Some can only be used with specific types of heat emitters. The cost and local availability of certain fuels obviously has a big impact on heat source selection.

CirculatorOften referred to as a pump, the circulator is the device that “motivates” fluid to flow through the

system in the intended direction, and at a suitable rate. The key component within a circulator is its impeller, which is rotated by an electric motor. As water flows through the spinning impeller mechanical energy called “head” is transferred to the fluid. The evidence of this added mechanical energy is higher pressure at the circulator’s discharge port compared to its inlet port.

Water always flows from an area of higher pressure to an area of lower pressure. The higher pressure water leaving a circulator wants to get back to that circulator’s inlet. It will do so through any available pathway. The fundamental concept in any hydronic system is to create piping pathways that let water carry heat throughout the building as it flows from the circulator’s outlet back to its inlet.

expansion tank

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heat released to building

circulator flow check

air separator

purging valve

make-up water assembly

propane input

boiler high limit

controller

room thermostat

pressure relief valve

propane-fired boiler

backflow preventerpressure reducing valve

The basic components in a hydronic system

An example of a modern wall-hung propane-fueled boilerSource: Triangle Tube

Figure 4-1

Figure 4-2

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Figure 4-3 shows a typical residential scale hydronic circulator. Such a product is specifically known as a “wet-rotor circulator.” It is entirely cooled and lubricated by the fluid passing through it, and does not require oiling as some earlier generation circulators do. Wet-rotor circulators have been in use for over three decades and have earned a reputation for reliability and quiet operation.

Many modern circulators can operate at different speeds depending on the circuit they are installed in. A switch on the junction box selects the operating speed.

Air separatorAny closed-loop hydronic system operates best when free of internal air. Some hydronic systems can’t even produce flow until most of the air in the piping has been expelled.

An air separator is a component specifically designed to extract air bubbles from the flowing water and channel them to a venting device where they are automatically ejected from the system. Many different types of air separators are currently available. All function by reducing the fluid’s flow velocity, as well as providing surfaces that air bubbles can cling to as they rise toward a venting device. Air separators function best when located near the outlet of the heat source, where the hottest fluid in the system passes through them. This is where molecules of oxygen, nitrogen and other gases are most likely to coalesce into bubbles that can be captured and ejected.

Flow-check Valve An important but often overlooked fact of hydronic heating is that hot water wants to move up and cool water wants to move down. This happens because hot water is less dense and therefore lighter than cool water.

If an unblocked flow path exists between an area of heated water and an area of cool water, nature makes sure a slow but persistent flow is established in an attempt to equalize these temperatures. Such a flow can occur even when all circulators in the system are off.

This natural convection current has been called many things, including “ghost flow”, “thermosyphoning” and “heat migration.” It can result in many aggravating problems by moving heat into area of the building where it’s not needed—a sort of “thermal leak” in the system.

A modern multi-speed wet-rotor circulator

A modern air separator

Figure 4-3

Figure 4-4

Example a flow-check valve

Figure 4-5

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A flow-check valve is one way to prevent such a situation. It contains a weighted metal plug that seats over the opening in the valve. This plug is heavy enough to block flow until the circulator turns on, at which time the plug pops up allowing flow through the valve. As soon as the circulator stops, the plug drops back down to block flow through the valve (in either direction).

Some hydronic circulators are now available with internal spring-load flow check valves. These eliminate the need to install a flow check valve in the circuit, and generally reduce installation cost.

Expansion Tank All fluids expand when heated. If a closed-loop hydronic system where completely filled with water the pressure in that system would rise rapidly as soon as the water temperature increased. Dangerously high pressures that could rupture piping components would quickly develop.

To prevent this, all closed loop hydronic systems must have an expansion tank. This tank contains a sealed internal chamber filled with pressurized air. The air is separated from the water in the system by a flexible rubber diaphragm. As the water is heated the sealed air volume behind the diaphragm is partially compressed by the expanding water, system pressure

increasing only slightly. When the system turns off and the water cools, the pressurized air volume expands as the water shrinks back to its original volume.

Pressure Relief ValveThe forces that expanding water can generate are very powerful. To prevent dangerously high pressures from occurring every closed-loop hydronic heating system must be equipped with a pressure relief valve. Most systems used in residential or light commercial buildings have pressure relief valves rated at 30 pounds per square inch (psi). Anything that allows internal pressure to climb to this setting will open the valve and immediately release fluid from the system, lowering its pressure.

Pressure relief valves should always be installed with their stem in a vertical upright position as shown in figure 4-7. Most are installed directly into the boiler or close to it. They should be equipped with a discharge pipe that ends near a floor drain. This pipe cannot contain any type of valve or flow restrictor. The lever

at the top of the valve can be lifted to verify proper operation. This should be done during annual maintenance checks.

Control SystemAn ideal hydronic heating system would always generate and deliver heat to the building at exactly the same rate the building loses heat to the outdoors. Such a “fully modulating” system could vary heat output from zero to full capacity as necessary.

Unfortunately, such full modulation is not currently possible for combustion type heat sources. In lieu of this, many hydronic control systems regulate heat output by turning the heat source and circulator(s) on and off. Heat is delivered to the building in intervals, the length of which depends on how large the load is. For example, on a very cold day, a properly sized boiler would remain on most of the time. However, during a milder day the heat source may only be on 10-25 percent of the elapsed time. The length of the on-cycle

and off cycle determines the total heat delivered to the load over a given time. A room thermostat similar to that used in other heating systems controls this on/off cycling.

Example of a diaphragm-type expansion tank

A manually-reset temperature limit control

Figure 4-8

Figure 4-6

Figure 4-7

A pressure relief valve

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Hydronic heating systems also have controls that regulate the water temperature delivered to different parts of the system. It is not uncommon for a boiler to deliver 170 ºF water to fin-tube baseboard heat emitters while at the same time delivering 110 ºF water to a radiant floor slab in a different part of the same building.

Still other controls provide safety against excessive high temperatures or water loss in the system. In most situations, these controls are required by code on all hydronic systems. A specific type of safety control called a manual reset high limit—shown in figure 4-8—turns off the boiler and prevents it from automatically restarting if water leaving the boiler reaches a set temperature. Think of this device as a “circuit breaker” for water temperature. Figure 4-9 shows a modern microprocessor controller for regulating water temperature in the distribution system based on outdoor air temperature.

Make-Up Water AssemblyAll hydronic systems experience minor pressure drops over time. Sometimes it’s caused by air being expelled from vents. Other times it’s the result of evaporation from valve packings or circulator gaskets. Still other times it’s caused by water loss when a component is serviced.

An automatic make-up water assembly feeds new water into the system whenever the system’s pressure drops below a preset value, typically in the range of 10 to 20 psi. Hence it “makes up” for minor water losses.

A typical make-up water assembly consists of a backflow preventer, pressure reducing valve, and shut off valve.

The backflow preventer does just what its name implies. It prevents any fluid in the hydronic system from migrating backward into the building’s potable water piping. Most plumbing and mechanical codes mandate a backflow preventer on any hydronic system connected to a building’s potable water system.

The pressure reducing valve detects when the system’s pressure drops below a set lower limit and responds by allowing water in to restore system pressure.

It’s important to understand that following their initial filling and air purging, properly functioning closed-loop hydronic systems require only minor amounts of makeup water. Large amounts of fresh water are NOT good for closed loop systems containing iron or steel components. The dissolved oxygen in fresh water encourages corrosion and sludge formation. Frequent feeding of fresh water through the pressure reducing valve is a sign the system needs servicing.

Purging ValvesWhen a hydronic system is put in service it’s important to rid the system of air as it is filled with water. Purging valves are used in combination with the makeup water assembly to establish a rapid water flow through the system as it is filled. This is called purging. The rapid flow displaces air bubbles and pulls them along with the water. The mixture of water and air exits through the side port of the purging valve. When this exiting stream is free of air bubbles

Figure 4-9 Figure 4-10

Figure 4-11

A controller that adjusts boiler temperature based on outdoor temperature.

An automatic make-up water assembly that maintains system pressure. Courtesy of Caleffi North America

Example of a purging valve for removing air from the system. Courtesy of Webstone Valve

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the purging process is complete, and the side port of the purging valve is closed. The use and correct placement of purging valves is essential to properly filling the system and preparing it for operation. An example of a purging valve is shown in figure 4-11.

Heat EmittersAll hydronic heat emitters extract heat from water flowing through them, and deliver that heat to the building space in which they are located. However, various types of heat emitters use different forms of heat transfer to accomplish this task.

Some devices, like the fin-tube baseboard (see figure 4-12), and fan-coils rely on convective heat transfer. They directly heat room air as it passes through them. The heated air flows into the room carrying the added heat with it.

Other types of hydronic heat emitters rely on thermal radiation to carry the majority of their heat output into the room. An example of such a heat emitter is a concrete slab with embedded tubing. Figure 4-13 shows tubing installed over polystyrene insulation awaiting the concrete slab.

Although the term “thermal radiation” may sound ominous, it is simply low intensity infrared light. Such radiation is completely natural and not harmful in any way. It behaves similar to visible light, but our eyes can’t see it. It travels out from the heat emitter and is quickly absorbed by the objects and surfaces within the room. The instant thermal radiation strikes these surfaces it ceases to exist as radiation and becomes heat, warming the object that absorbed it. The warming of objects and room surfaces significantly improves comfort.

Where Does This Equipment Go In A Building?Traditionally, the boiler of a residential hydronic heating system is installed in the basement or crawl space. An example of such an installation is shown in figure 4-14. In commercial buildings the boiler is typically be installed in a separate mechanical room.

Although such installations are common, they are not the only option. Many modern propane-fueled boilers are compact enough to be installed in spaces such as laundry rooms, utility closets, pantries, or garages. Such boilers are often wall-mounted as shown in figure 4-15 (next page).

Don’t be fooled by the small size of wall hung

boilers. In most cases they’re able to supply all the space heating and domestic hot water requirements of a typical home.

Most of the piping used in a hydronic distribution system is usually concealed within the wall and floor structure of the building. This is possible because the piping is usually less than 1-inch in diameter, and easily slides through holes in floor joists or studs. Some of the distribution systems discussed in section 7 of this publication make use of 1/2-inch and even 3/8-inch diameter flexible tubing as shown in figure 4-16. This small flexible tubing is easily and quickly

Figure 4-12

Figure 4-13

Figure 4-14

An example of a fin-tube baseboard convector. Courtesy of Weil-McLain

Flexible hydronic tubing that will be embedded in a concrete floor. Courtesy of HYtech Heating

Example of a boiler installed in a base-ment. Courtesy of ECR International

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pulled through building structures much like electrical cable. The remaining piping and components are typically mounted close to the boiler as shown in figure 4-17.

The location of heat emitters depends upon their design. One of the traditional hydronic heat emitters used in North America is called fin-tube baseboard. It consists of a metal enclosure a few inches tall that houses a copper tube with closely spaced aluminum fins. Fin-tube baseboard is installed along the base of walls in place of traditional wooden baseboard as shown in figure 4-18.

Another type of hydronic heat emitter is called a panel radiator. Such radiators are

installed on walls and come in a wide variety of shapes, sizes, and colors.

A special type of panel radiator intended for use in bathrooms, kitchens, and vestibules is called a “towel warmer.” It not only warms the room, but also provides a rack that can quick dry damp towels, gloves, and garments. An example is shown in figure 4-19.

The ultimate “out-of-sight” hydronic heat emitter is a heated floor, wall, or ceiling. Flexible tubing is embedded within one or more of these room surfaces during construction, and is completely out of site when those surfaces are finished. The only difference that will be noticed is gentle radiant warmth from what might otherwise be cold uninviting surface.

We’ll discuss options for propane-fueled boilers, distribution systems, and

heat emitters in more detail in sections 5, 6 and 7.0

Figure 4-15

Figure 4-16

Figure 4-18

Figure 4-19

Figure 4-17

A wall-mounted boiler installed in a laundry room. Courtesy of Monitor Products

Example of 1/2-inch size flexible PEX-AL-PEX tubing.

Typical boiler room piping. Courtesy of HYtech Heating

A short length of fin-tube baseboard

Wall hung towel-warmer radiator. Courtesy of Myson

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Section 5: Propane-Fueled Heat Sources

Although there are many options for hydronic heat sources, one of the most versatile is a modern propane-fueled boiler. Almost every boiler designed

to operate with natural gas can be easily configured to operate with propane. This includes traditional cast-iron, steel, and copper tube boilers, as well as the ultra-high efficiency modulating / condensing (mod/con) boilers. When fueled by propane, all such boilers provide clean combustion, high efficiency, and very low sound levels.

Cast-Iron BoilersFigure 5-1 shows an example of a propane-fueled boiler that has a cast-iron heat exchanger. Cast-iron boilers have been used for over a century. They are often found in traditional higher temperature hydronic systems such as those supplying fin-tube baseboards. They can also be used in modern low temperature radiant panel heating systems, as well as “multi-load / multi-temperature” systems that supply heat to pools and snowmelting subsystems.

One very well established advantage of cast-iron boilers is long life. It’s not uncommon to find such boilers operating 30 years

after they were installed. Very few other home appliances can claim such a long service life. As with any boiler, this long life is the result of proper application and annual maintenance.

Cast-iron boilers also provide significant thermal mass to the system. This provides stability to systems that supply several independently-controlled zones, and prevents short-cycling.

Copper Tube BoilersAnother type of boiler that can operate with propane has a heat exchanger constructed of specially formed copper tubing. Because copper transfers heat better than cast iron, less metal is required for the boiler’s internal heat exchanger. This results in a lighter, and more compact boiler. Such characteristics are desirable in situations where space is limited, or where low weight is needed due to access or structural limitations of the building.

The lower thermal mass of a copper tube boiler allows it to reach normal operating temperatures quickly after start-up.

Both cast-iron and copper tube boilers are categorized as conventional boilers. They are intended to operate at temperatures high enough to prevent water vapor in the exhaust stream from condensing (e.g. changing from vapor to liquid) within the boiler or its vent pipe.

Well-maintained cast-iron and copper tube boilers typically operate with combustion efficiencies in the range of 85 to 87 percent. They are usually vented through a chimney, although some cast-iron and copper tube boilers can be vented directly through the exterior wall of building and thus eliminate the need for a chimney.

Modulating / Condensing BoilersDuring the last decade a new class of propane-fueled boilers has steadily gained market share—mod/con (modulating burner, condensing) boilers. These boilers are equipped with heat exchangers made of stainless steel or aluminum, and designed so that vapors produced during combustion can condense within the boiler – just the opposite intent of the previously discussed conventional boilers. Why the difference? In a word: Efficiency.

Boilers capable of condensing all the water vapor in the exhaust stream will experience a nominal 10 percent increase in thermal efficiency relative to boilers that do not operate with such condensation. In the right application, a propane-fueled mod/con boiler can attain thermal efficiencies of 95 percent or more.

The stainless steel or aluminum heat exchangers used in mod/con boilers are specifically designed to operate under these conditions without the corrosion that would beset cast-iron, steel or copper boilers under the same conditions.

The key to operating a mod/con boiler at sustained high efficiency is to match it with a low temperature distribution system. Slab-type radiant floor heating is a good example of such a low temperature system. Without such low temperature operation, flue gases will not condense to the extent necessary to achieve sustained high efficiency.

Figure 5-1

Figure 5-2

Example of a cast-iron boiler. Courtesy of Weil-McLain

Example of a copper tube boiler. Courtesy of Lochinvar

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Many mod/con boilers are small enough and light enough for wall mounting as shown in figure 5-3. This conserves floor space within buildings and allows mechanical rooms to be smaller than with traditional floor-mounted boilers. The extremely low sound levels at which these boilers operate do not create annoying noises inside the building.

Mod/con boilers are designed as “sealed combustion” appliances. All air needed for the combustion process is drawn from outside the building, typically through PVC pipe as small as 2-inch in diameter. The cooled combustion gases leaving the boiler are also directed outside through a separate PVC, CPVC, or stainless steel pipe. A boiler using sealed combustion does not draw any air from within the building. This prevents interference between the combustion stream of the boiler and others fans that may be operating within the building. Sealed combustion also prevents contaminants such as vapors from cleaning fluids or chlorine bleach that might be present within the building, from being drawn into the boiler where they can cause corrosion. Finally, sealed combustion boilers are very safe in that they constantly monitor the proper flow of exhaust gases. If the internal combustion fan cannot establish and maintain proper flow the boiler automatically turns off until it can be serviced.

Multiple Boiler SystemsMost people think that all houses with hydronic heating have a single boiler. They assume that a small boiler is used in a small house, while a large boiler is required in a big house. Although this is common for many single family houses, it’s not the only possibility.

Many large homes with multiple hydronic heating loads such as space heating, domestic water heating, pool heating, and snow-melting are excellent candidates for a multiple boiler system.

The concept of a multiple boiler system is simple: Instead of using a single boiler with sufficient heat output to handle all loads, two or three smaller boilers with the same total heating capacity are installed. There are several reasons that favor this approach.

First, having multiple boilers allows for partial heat delivery if one boiler is not operating due to a malfunction. Simply put, it’s better to have some heat rather than no heat. This is especially important in locations where extreme temperatures might freeze up non-operational systems.

Second, multiple boiler systems deliver higher seasonal efficiencies compared to a single large boiler of equivalent heating capacity. This comes from the ability of a multiple boiler system to “track” the total heating load of the system and only operate the boiler(s) necessary to meet that load at any given time. This is called “staging” the boilers. Thus, when a small zone needs space heating only one of three boilers in a multiple boiler system may operate. However, when two or three showers go into

Figure 5-3

Figure 5-4

A wall-hung propane-fueled mod/con boiler. Courtesy of HYTech Heating

A residential multiple boiler system supplying several loads. Courtesy of Paul Rohrs

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simultaneous operation, or it’s time to melt snow off the driveway, all three boilers will automatically turn on. The intelligence to operate a multiple boiler system is provided by a small microprocessor-based controller. In some cases this intelligence is even built into the boiler’s electronics and only needs to be activated when the system is installed.

Finally, multiple boiler systems use smaller lighter boilers that are easier to move into or out of a building compared to a single large boiler. This is especially important in retrofit applications.

Figure 5-4 (previous page) is an example of a multiple mod/con boiler system in a residential application. Notice that these boilers supply several independently controlled circulators seen at on left side of the figure. The PVC tubing used for combustion air supply and venting is visible behind the boilers, as is the PVC condensate drainage piping required on all mod/con boilers.

Both conventional and mod/con boilers can be set up in multiple boiler groups. An example of a residential system with dual cast-iron boilers is shown in figure 5-5. A system with dual wall-mounted mod/con boilers is shown in figure 5-6. Section 7 of this publication shows how the piping is configured in such systems.

Which Propane-Fueled Boiler is Right for You?Asking which propane-fueled boiler is right for you is like asking which automobile, or which house, is right for you. There are literally hundreds of propane-fueled boilers on the North American market in various models and sizes supplied by dozens of manufacturers.

From a technical standpoint, the use of cast-iron or copper tube boilers makes sense when the distribution system the boiler serves consistently operates at water temperatures of 140 ºF or higher. This is common for traditionally designed systems using fin-tube baseboard, or hydronic fan-coils as heat emitters.

When the distribution system can operate at water temperatures lower than 140 ºF for many hours each year a mod/con boiler will provide higher fuel efficiency, albeit at a higher installed cost.

It’s also important that the boiler selected can be locally serviced. Few would debate that mod/con boilers are more sophisticated devices than traditional cast-iron and copper tube boilers. It’s imperative that those installing such products are fully familiar with their operation and can service them when necessary.

Another factor that might tip the scales is the type of venting desired. As previously mentioned, many conventional boilers are designed to be vented by a chimney. Some are available for side-wall venting. In situations where a chimney is not possible, boiler selection will be limited to those units that can be sidewall vented.

Boiler selection should only be done by a knowledgeable and competent heating professional. The boiler’s heating capacity should be determined based on a proper heating load estimate of the building. Without such an estimate, the boiler can only by sized by guessing. This usually results in oversizing, and in some cases gross oversizing. The result is a needlessly expensive boiler that operates at reduced fuel efficiency. The owner pays more for the boiler and related hardware installation, as well as more for increased fuel usage due to reduced efficiency.

Figure 5-5

Figure 5-6

Two cast-iron boilers operated as a multiple boiler system

Two wall-mounted mod/con boilers operated as a multiple boiler system. Courtesy of Foley Mechanical

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Propane-Fueled Water Heaters as Hydronic Heat SourcesThere are situations where a small hydronic system may be incorporated into a home with forced-air or other type of heating. An example would be use of hydronic floor heating in the bathrooms and kitchen, with forced air heating elsewhere. In such situations it’s possible to draw sufficient heat for the hydronic system from a specialized water heating device. An example of such a device is shown in figure 5-7.

This propane-fueled water heater contains an internal heat exchanger coil in the upper portion of the tank. This coil can extract heat from the tank to serve as the heat source for the small hydronic distribution system. The domestic water in the tank never contacts or mixes with the water in the hydronic system. This allows a single compact tank to supply both domestic hot water and a small hydronic heating load.

Another appliance that has gained significant market share in recent years is the propane-fueled tankless water heater. These devices turn on their burner as soon

as domestic water begins flowing through them on its way to hot water faucets. They do not store water as does a conventional tank-type water heater.

Given their size and heating capacity, such units can serve as hydronic heat sources in certain types of applications. An example of a tankless water heater that could be used for hydronic heating is shown in figure 5-8

It is important that hydronic system designers understand the differences between tankless water heaters and conventional boilers. Tankless water heaters may require changes in circulator sizing or piping design relative to those used for conventional boilers.

Whenever a water heater is used as a hydronic heat source a thermostatic mixing valve must be installed in the piping supplying hot water to the fixtures in the building.

SummaryThere are many types of propane-fueled boilers and water heaters currently on the North American market. They are available in a wide range of heating capacities, sizes, venting options, and materials. Given such options it’s possible to closely match a boiler or water heater to a specific hydronic heating requirement. Doing so assures that appliance will operate reliably for many years as it provides superior comfort and high efficiency.

Figure 5-7

Figure 5-8

Propane-fueled tank-type water heater with internal heat exchanger coil that serves as a hydronic heat source. Courtesy of Bradford White

Propane-fueled tankless water heater that could serve as a hydronic heat source. Courtesy of Rinnai

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Section 6: Heat Emitter Options

Hydronic heat emitters remove heat from water flowing through them and deliver it to occupied spaces. They vary in size from small “kickspace” heaters installed

under cabinets to the entire floor of a large commercial building. They also vary in the physical processes used to deliver their heat to the space.

This section gives an overview of the some modern hydronic heat emitters as well as a brief description of their performance characteristics. It also shows options for the distribution systems these heat emitters can be used in.

Finned-Tube BaseboardMost residential hydronic heating systems installed in North America up through the 1980s used finned-tube baseboard convectors for heat emitters. This type of heat emitter continues to be a staple in North American hydronics. Their heat output per dollar of installed cost is hard to beat. A close up of a typical finned-tube baseboard is shown in figure 6-1.

Finned-tube baseboard consists of two basic components: The element, and the enclosure. The element is copper tubing in sizes ranging from 1/2-inch to 1-inch, with mechanically attached aluminum fins. These fins conduct heat away from the tube and transfer it to surrounding air by convection. The warmed air rises out of the upper slot of the steel enclosure. Cool air near the floor flows into the bottom slot to sustain the process.

The function of the enclosure is to channel air through the element, as well as protect it. The enclosure must be installed so air can freely flow into the bottom opening. Most baseboard enclosures have a pivoting damper along the air outlet slot, which can be adjusted to partially regulate this air flow and thus the rate of heat output.

Finned-tube baseboard is typically sold in straight lengths between 2 to 10 feet long. The finned-tube element and enclosure are sold together. Manufacturers also offer accessories for the enclosure including end caps, couplings, and corner trim. Heat output from finned tube baseboard depends on the water temperature supplied to the element. The heat output of a typical residential-class finned-tube baseboard versus the average water temperature in its element is shown in figure 6-2. Traditionally, finned-tube baseboards are sized assuming water temperatures in the range of 150 to 200 ºF. Such temperatures are within the normal operating range of conventional boilers, and high enough to prevent sustained flue gas condensation in the boiler.

If finned-tube baseboard will be used with a mod/con boiler it should be sized for lower supply temperatures in the range of 120 to 140 ºF. These lower temperatures will necessitate substantially longer baseboards to achieve equivalent heat output relative to those required for higher temperature systems. The designer should be certain there is ample wall space to accommodate these longer lengths prior to committing to this approach. Assuming sufficient wall space does exist, operating baseboard at lower water temperatures allows a mod/con boiler to achieve thermal efficiencies in the 90 to 95 percent range, albeit at the added cost of longer baseboards.

Designers should keep in mind that residential-class finned-tube baseboards are not designed for heavy traffic areas or other situations where it might be subject to physical impact. They should also not be used in high moisture environments, which encourage corrosion of the steel enclosure.

Traditionally, finned-tube baseboards have been installed in series piping circuits as shown in figure 6-3 (next page).

0

100

200

300

400

500

600

700

65 85 105 125 145 165 185 205 Average water temperature in baseboard (ºF)

Base

boar

d he

at o

utpu

t pe

r foo

t of e

lem

ent (

Btu/

hr/ft

)

Air temperature near floor of room assumed

to be 65 ºF

Figure 6-1

Figure 6-2

Image courtesy of HYTech Heating

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Although such distribution systems are still viable, they do have limitations. First, the water temperature decreases as it passes through each heat emitter (finned-tube baseboard or other type). This implies that baseboards farther “downstream” receive water temperatures significantly lower than those near the beginning of the circuit. This effect must be taken into account through careful design. The result will be longer baseboards to achieve a given rate of heat output depending on how far downstream that baseboard is located.

Secondly, very little can be done to adjust the heat output of a given heat emitter in a series circuit without affecting the heat

output of all heat emitters on that circuit. For example, assume one baseboard in the series circuit was inadvertently oversized for the heating load of the room it serves. If the flow rate in the circuit were lowered to reduce heat output of this baseboard it would also reduce heat output from all other baseboards on the circuit.

Finally, soldering hundreds of pieces of rigid copper tubing together to construct series circuits is labor intensive compared to other installation methods now available.

A modern alternative to series distribution systems, a “homerun system,” is shown in figure 6-4. Each baseboard (or other heat emitter) has its own supply and return tubing from a manifold location. The tubing used is flexible PEX (crosslinked polyethylene) or PEX-AL-PEX (composite of PEX and Aluminum). Such tubing is easily routed through buildings in continuous pieces from the manifold location to each heat emitter.

Homerun distribution systems supply the same water temperature to each baseboard and thus eliminate the temperature drop associated with series circuits. They also allow flow adjustment to each baseboard when needed to regulate heat output. Flow to any baseboard can be completely turned off, while flow to other baseboards continues. This allows room-by-room comfort control. Given these advantages the homerun distribution system is the preferred method of connecting finned-tube baseboard in modern hydronic system installations.

Panel RadiatorsLong a staple in European hydronic systems, panel radiators are quickly gaining popularity in North America. Available in hundreds of shapes, sizes, colors, and tubing designs, steel panel radiators are very different from their cast iron predecessors. An example of an installed panel radiator is shown in figure 6-5.

propane input

propane-fired boiler

baseboard #1 baseboard #2

baseboard #4

baseboard #3

SERIES CIRCUIT

propane input

propane-fired boiler

baseboard #1

baseboard #2

baseboard #3

thermostatic radiator valves

(TRV)

to / from other heat

emitters

manifold station

Figure 6-3

Figure 6-4

Figure 6-5

Image courtesy of DiaNorm

Sec6:23

This style of panel is fabricated from preformed steel sheets welded together at edges and across the face of the panel. As warm water circulates through the channels in the front surface it emits gentle radiant heat to the room and its occupants. Steel fins welded to the rear of the panel enhance convective heat output.

A cut-away of a typical panel radiator is shown in figure 6-6. The left side shows the finished surface and water channels. The right side shows the folded steel fins attached to the rear of panel. Also visible are the supply and return connections at the bottom right, and thermostatic radiator valve at upper right. This valve regulates water flow through the panel and hence its heat output.

This type of panel is available in a wide range of widths, heights, and depths as shown in figure 6-7.

There are also designer panel radiators as shown in figure 6-8 and 6-9. These contemporary designs are true interior design elements that also deliver silent comfort to the spaces they serve.

Panel radiators are also ideally suited for homerun distribution systems as depicted in figure 6-10. Heat output from each panel can be individually regulated for precise room-by-room comfort control. This is all accomplished without need of electric room thermostats and their associated wiring, which speeds installation and reduces cost.

Figure 6-6

Figure 6-8

Figure 6-10

Figure 6-9

Figure 6-7

Image courtesy of DiaNorm

Image courtesy of DiaNorm

Image courtesy of Vasco

Image courtesy of Myson

Image courtesy of DiaNorm

Sec6:24

Hydronic Air HandlersThere are times when a “hybrid” approach to space heating, one that combines elements of both hydronic and forced air, is ideally suited to a project. An example would be when wall space is not available for other types of heat emitters, or when a forced-air system will also be used for summer cooling.

Hydronic air handlers make this hybrid approach possible. They receive heat from a hydronic distribution, but deliver that heat to the building using forced-air. The air flow is created by a small blower or fan within the unit. Room air moves across a “coil” consisting

of copper tubing and closely spaced aluminum fins. Heat is transferred from the copper tubing to the aluminum fins, and then to the air stream. The heated air may be blown directly into the space, or travel through ducting to enter the space from several locations at the same time.

Hydornic air handlers include wall-mounted “console” units, as well as larger horizontal and vertical “cabinet” air handlers. Console units are used to heat individual rooms. Cabinet air handlers are typically used to heat a zone consisting of two or more rooms. A representation of zoned air handler system is show in figure 6-11

It’s also possible to add a chilled water coil or refrigeration coil to some types of hydronic air handlers. This enables the unit to supply cooling in summer as well as heat in winter. Air handlers

are also occasionally used as a “supplemental heat emitters” in spaces with especially high heat losses.

Radiant Panel HeatingNothing demonstrates the versatility of hydronic heating better than site-built radiant panels. In short, this is the concept of integrating small flexible polymer tubing into the floors, walls, and ceilings of rooms. As warm water passes through this tubing heat

is conducted to the surface and released into the room, mostly as low intensity radiant energy, resulting in unsurpassed comfort.

Hydronic radiant panel heating has been used for decades. Early systems used copper or steel tubing and boilers with minimal controls. Although unrefined by today’s standards, these systems produced outstanding comfort relative to alternative methods of the time.

The development of crosslinked polyethylene (PEX), and composite (PEX-AL-PEX) tubing revolutionized the hydronic radiant panel heating market in North American starting in the 1980’s. Today there are several methods of integrating this durable tubing into floors, walls, and ceilings. We will discuss the most common approaches.

Radiant Floor Heating The best-known type of hydronic radiant panel is a heated concrete floor. Because the concrete slab is already a part of the building, this approach has a low cost per square foot compared to other methods of radiant panel construction. Although the resulting floor is visually indistinguishable from a standard concrete floor, the difference is room comfort relative to other methods of heating is very noticeable.

The typical construction of a hydronically heated slab is shown in figure 6-12.

to/from other zoned air handlers

zone valves

purge valves

air handler

air handler

air handler

air filtercoil

blower

circulator

boiler

Figure 6-11

Example of slab-on-grade floor heating. Courtesy of IPEX Inc.

Figure 6-12

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The installation starts with placement of a polyethylene vapor barrier and extruded polystyrene foam insulation over a level and firm sub grade. The insulation limits heat loss from the underside of the slab to the soil. Steel mesh placed over the foam provides structural reinforcement for the slab. PEX or PEX-AL-PEX tubing is attached to this mesh using wire or plastic ties. All tubing circuits are pressure tested to ensure there are no leaks. This is followed by the concrete placement and finishing.

Heated slabs can be covered with various finish floorings including ceramic tile, stone, vinyl, engineered wood and carpet. However, heat output from the floor is strongly dependent on the R-value (thermal resistance) of the finish floor. For the best performance the finish floor R-value should be as low as possible.

Thin Slab Floor HeatingAnother method radiant floor construction uses a thin (1.5-inch to 2-inch thick) layer of concrete or poured gypsum underlayment over tubing that has been previously fastened to a plywood subfloor. This is called a thin-slab system, an example is shown in figure 6-13.

Thin-slabs provide good heat output at low water temperatures similar to slab-on- grade systems. They require a floor structure designed to handle the added weight of the slab, (typically 14 to 18 pounds per square foot). Like a heated slab-on-grade floor they can be covered with a variety of finish floorings. The underside of the floor framing should always be insulated to a minimum of R-19 to force most of the heat output in the upward direction.

Tube-and-Plate Floor HeatingStill another method of radiant floor heating uses preformed aluminum plates to extract heat from the tubing and disperse it across the floor. These thin aluminum plates can be installed

above or below a wood subfloor. Above floor installation is typical when a nailed-down hardwood finish floor will be installed. Below floor plates are common for use with tile or carpet finish floor. An example of an above floor tube and plate installation is shown in figure 6-14.

Tube-and-plate radiant panels are much lighter than thin-slab radiant panels. They also respond faster to temperature changes because of their lower thermal mass. Again, a minimum of R-19 underside insulation is critical to ensure that most heat output goes upward into the room.

Radiant Wall HeatingThe same type of tube and plates used in floor heating can also be adapted to wall heating. Such systems are excellent in situations where high thermal resistance floor coverings are desired, and thus floor heating is not an option. Their low thermal mass allows rapid response. The appearance of the finished wall gives no clue that it’s a heat emitter capable of warming the entire room.

Figure 6-13

Figure 6-14

Figure 6-15Example of thin-slab floor heating. Courtesy of IPEX Inc.

Example of above floor tube-and-plate floor heating. Courtesy of IPEX Inc.

A radiant wall panel under construction

Sec6:26

A partially installed radiant wall is shown in figure 6-15 (previous page). The aluminum heat transfer plates are fastened to foil-faced insulation strips using contact cement. The tubing is then snapped into the plates and drywall is screwed in place to complete the assembly.

It’s important that furniture or other large objects are not placed directly in front of or against heated walls. Doing so reduces radiant heat delivery into the space.

Radiant Ceiling HeatingMany people do not believe it’s possible to heat a room from the ceiling down. They rationalize this by stating that “heat rises.” This is not true. Warm air rises due to its lower density, but heat travels from warm areas to cold areas regardless of direction. This is especially true of radiant heating. The low intensity infrared light emitted by a warm ceiling travels down into the room just like visible light from a ceiling lamp. The difference is that our eyes cannot see the infrared light. The floor and other objects in the room absorb this radiant energy. The resulting comfort is excellent.

Like radiant walls, radiant ceilings are an excellent option when floor heating is ruled out due to high thermal resistance floor coverings. It can be installed using the same materials and methods shown in figure 6-15. The only difference it that it’s fastened to ceiling framing rather than wall framing.

Radiant ceilings also respond quickly to thermostat adjustments. They can turn on quickly when it’s time to raise the comfort level of a room from a previous setback condition. They can also turn off quickly in response to internal heat gains from sun, people or equipment. Radiant ceilings can also operate at higher heat output rates because people are not in direct contact with the surface as they are with heated floors. This implies that a radiant ceiling panel can be smaller than a radiant floor panel and yet produce the same heat output.

Radiant ceilings are very unlikely to be covered by other materials over the life of the building, and thus can perform for decades regardless of changes in floor coverings, furniture arrangement, etc.

Finally, radiant ceilings are excellent above large tub platforms, especially when those platforms are surrounded by lots of windows as shown in figures 6-16 and 6-17. They are also a good choice for bedrooms where furniture placement would partially block heat output from floors.

Designers should remember that radiant floors, walls, and ceilings can be combined within the same system. An example would be a heated slab floor in the basement combined with a tube and plate

floor system in the main living areas, and radiant ceiling heating in bedrooms. It’s also possible to combine radiant panels with other hydronic heat emitters like finned-tube baseboard and panel radiators. Examples of such multi-load / multi-temperature systems are shown in section 7.

Figure 6-17

Figure 6-16

This tub platform does not provide sufficient area for floor heating

The ceiling above the tub is heated to gently warm the tub and surround platform surfaces

Sec7:27

Section 7: Other Loads Supplied by Hydronics

Although most people think of a propane-fueled boiler as a device for space heating, it can also provide heat to several other loads in and around the building. This

ability is unique to hydronics. When properly designed, such multi-load hydronic systems increase combustion efficiency relative to using separate heating appliances for each load. Such systems also reduce installation cost by eliminating redundant hardware. It’s a win/win scenario, and represents the essence of modern hydronics technology.

This section describes several loads, other than space heating, that are commonly served by a multi-load hydronic system. It goes on to show examples of how all these loads can be handled by a single propane-fueled heat plant.

Abundant Domestic Hot WaterDomestic hot water is one thing that no modern home, small or large, can do without. It must be available 24/7 in quantities that allow occupants to use it as they choose. Few nuances around the home are as aggravating as not having enough hot water to finish a long shower, or not being able to use the clothes washer when someone is filling a bathtub.

A distinct trend in residential construction has been increased interest in luxury bathrooms. The North American plumbing industry has done a superb job of promoting such bathrooms as luxurious escapes from the cares of life. Central to that concept is

surrounding oneself with lavish amounts of warm water, be it in a deep whirlpool tub or a simulated tropical downpour showering experience. An example of a luxury residential shower is shown in figure 7-1.

Homes with several bathrooms can place very heavy demands on ordinary tank-type water heaters.

In some cases standard water heaters can’t keep pace with the demand, especially when several fixtures are in use at the same time. This forces the occupants to “schedule” showers or baths to avoid running out of hot water. The occupants are forced to conform to the ability of the water heater rather than their own convenience.

Why should owners of such homes, many of whom have spent lots of money for luxury bathrooms, have to compromise the usage of those fixtures based on limitations of the water heating equipment?

Fortunately, a properly configured propane-fueled boiler system combined with a high capacity hydronic water heater can supply such demands indefinitely. Such systems provide a modest amount of storage capacity for handling small hot water demands without need of operating the boiler every time a faucet is opened. They are also capable “ramping up” domestic hot water production to supply several bathrooms in simultaneous use.

The type of water heating device used in such systems is called an “indirect water heater.” It consists of a well-insulated hot water storage tank equipped with an internal heat exchanger. As the tank’s temperature begins to drop, the boiler is fired, and hot water from the boiler is circulated through this coil. The boiler water never mixes with the potable water in the storage tank. However, heat is quickly and efficiently transferred from the hot boiler water through the metal walls of the internal heat exchanger and into the cooler domestic water. The concept is shown in figure 7-2.

indirect water heater

space heating circulator

DHW tank circulator

domestic cold

water

domestic hot

water

internal heat exchanger

to/from space heating

propane-fired boiler

Figure 7-1

Figure 7-2

Example of a luxury shower / tub combination Piping schematic for an indirect water heater

Sec7:28

An example of an indirect water heater is shown in figure 7-3.

Indirect water heaters have several advantages compared to “direct-fired” water heaters.

First, this method of water heating requires only one heat source to supply both space heating and domestic hot water. This reduces

installation and maintenance costs relative to having separate burners for each load.

Second, this approach can usually heat water significantly faster than a typical direct-fired water heater. This is especially important in situations where several appliances are using hot water at the same time.

Third, because the heat exchanger surfaces within an indirect water heater do not get as hot as the elements in an electrical water heater, or the surfaces in a direct-fired water heater, they are less likely to build lime scale, which can reduce efficiency over time.

Finally, the combustion efficiency of a modern propane-fueled mod/con boiler is higher than that of a direct-fired water heater. Higher efficiency means less fuel is needed to produce a given amount of domestic hot water relative to other heating options.

A piping schematic for a hydronic system that provides both space heating and high capacity domestic water is shown in figure 7-4. All heat for the building as well as domestic water heating is generated by the propane-fueled multiple boiler system.

Special controls allow the system to treat domestic water heating as a “priority load.” When the hot water storage tank needs heat, all other loads in the system are temporarily turned off so the full output of the boilers can be dedicated to domestic water heating. Once the domestic hot water tank returns to the proper

temperature the other loads are allowed to come back online. This strategy has been successfully used for many years in all types of hydronic heating systems.

When properly sized, propane-fueled mod/con boilers can provide the heat generation needed to keep up with any demand for domestic hot water. This ensures that all bath and shower fixtures in the building can be operated without the concern for running out of hot water.

Hydronic Snow and Ice MeltingMany hydronically-heated buildings are located in areas that receive significant snowfall. This snow must be repeatedly cleared from steps, sidewalks, and driveways. Mechanical methods of snow removal include shoveling, snow blowers, and plowing. All have their pros and cons.

The alternative to mechanical methods of snow and ice removal is to do what nature does every spring – melt the snow and ice from pavements. This is an ideal task for modern hydronic heating technology. PEX or PEX-AL-PEX tubing can be embedded within

high capacity indirect water heater

domestic hot

water

hydraulic separator

space heating circulator

DHW tank circulator

space heating distribution

system

propane-fired mod/con

boiler system

domestic hot

water

boile

r ci

rcul

ator

s

Figure 7-3

Figure 7-4

Example of an indirect water heater

Use of a high capacity indirect water heater in combination with a multiple boiler system

Sec7:29

pavements similar to how they are built into interior floor slabs. These tubing circuits are filled with antifreeze solutions that can be heated and circulated when snow melting is required. As in a car, the antifreeze solution prevents any damage to the snowmelting components when the system is idle during subfreezing temperatures.

Hydronic snow and ice melting systems offers several benefits over traditional methods of snow removal.

They can provide fully automatic and unattended snow and ice • removal whenever required. They remove snow without creating banks or piles that often • lead to drifting and/or damage to landscaping. They eliminate the need for and cost associated with sanding • pavements. This also eliminates the associated mess and floor covering damage when sand is tracked into buildings. They eliminate the need for and cost • associated with salting, as well as the potential damage to landscaping and the surrounding environment. Pavement damage due to frost, • salt, and plowing is reduced. This is especially important for surfaces covered with pavers. Snow and ice-free pavements reduce • likelihood of slips, falls, or vehicular accidents. Snowmelting improves property • appearance in winter by eliminating snow banks and sand/salt residue.

An example of how tubing for hydronic snowmelting is installed in concrete paving is shown in figure 7-5.

Notice the insulation under the slab. This is necessary to prevent excessive heat loss to the soil under the pavement. It is also very important to slope the pavement and provide proper drainage for the melt water. Not doing so can result in melt water freezing back into ice.

Hydronic snowmelting can also be incorporated into asphalt pavements as well as those finished with pavers.

Snowmelting requires significantly more heat output per square foot of slab surface than does space heating. Snowmelting systems that serve entire driveways typically require heat production rates of several hundred thousand Btus per hour. This is usually handled by a multiple boiler system like that discussed earlier for high capacity domestic water heating. In the event that snowmelting and domestic water heating are required at the same time, the domestic water heating load is given priority. As soon as the hot water storage tank has recovered to its setpoint temperature heat is directed back to snowmelting. The large thermal mass of a heated pavement allows such an operation to go virtually unnoticed.

Figure 7-6 shows how the schematic of figure 7-5 can be modified to allow the multiple propane-fueled boilers to provide both high capacity domestic water heating and snowmelting.

Pool / Spa HeatingMost people who own swimming pools or spas consider heating them to extend the swimming season or simply enjoy the comfort of a spa year round. Traditionally, this is done with a direct-fired pool heater, electric pool heater, or specialized heat pump. However, the versatility of a propane-fueled boiler system in combination with hydronic distribution system allows the same boiler(s) that heats the house to heat the pool.

high capacity indirect water heater

domestic hot

water

hydraulic separator

space heating circulator

DHW tank circulator

propane-fired mod/con

boiler system

domestic hot

water

boile

r ci

rcul

ator

s

space heating distribution

system

stainless steel heat exchanger

mixing valve

embedded snowmelting circuits

This portion of the system filled with antifreeze solution

Figure 7-6

Multiple propane-fueled boiler system supplies domestic water heating and snowmelting.

trench drain

slope to drain

slope pavement away from building (also slope away from unmelted pavement)

route drainage to non-freezing location

embedded tubing

underslab insulation

grating

building foundation

melt water

Figure 7-5

Sec7:30

Think about it. The time of year when most outdoor swimming pools are in use does not correspond to peak space heating demand. During late spring and early fall the boiler may be doing little other than heating domestic water for the building. Why not use the available heating capacity of the boiler to heat the pool rather than install a separate pool heater? Doing so improves the efficiency of the existing boiler(s) and reduces the cost associated with installing an alternate means of pool heating.

Figure 7-7 demonstrates how the previous piping schematic can be expanded to include pool heating along with space heating, domestic water heating and snowmelting.

A stainless steel heat exchanger separates the chlorinated pool or spa water from the water in the hydronic system. Heat is readily passed from the hot boiler water to the pool water without ever mixing the two fluids. The pool’s filter pump provides flow through heat exchanger. Hot water from the boiler(s) is circulated through the other side of the heat exchanger whenever pool heating is required. A similar arrangement with smaller hardware would be used for spa heating.

Once again, the high heating capacity of a multiple propane-fueled boiler system comes into play. In this case, it enables rapid pool heating. Depending on the size and temperature of the pool, as

well as the installed boiler capacity, it’s possible to bring the pool temperature up 25 or 30 ºF within a 12 hour period. Very few residential size pool heaters come close to this heating ability. Some would require several days to bring an average residential pool from ambient temperature up to a comfortable swimming temperature.

SummaryA hydronic heating system with a propane-fueled boiler can supply just about any heating requirement associated with a house or commercial building. This ability is unmatched by forced-air, heat pump, geothermal, or electric heating systems. It allows efficient use of both propane and the hardware needed to convert it into heat. It then delivers that heat precisely when and where it’s needed. Multi-load systems are the essence of modern hydronics technology, and the key to the efficient use of Propane, Exceptional energy.

high capacity indirect water heater

domestic hot

water

hydraulic separator

space heating circulator

DHW tank circulator

propane-fired mod/con

boiler system

domestic hot

water

boile

r ci

rcul

ator

s

space heating distribution

system

stainless steel heat exchanger

mixing valve

embedded snowmelting circuits

pool filter

pool

pool pump

stainless steel heat exchanger

POOL HEATING

SNOW MELTING

DOMESTIC WATER

HEATING

Figure 7-7

Multiple propane-fueled boiler system supplies domestic water heating, snowmelting, and pool heating.

Sec8:31

Section 8: Case Studies

The combination of a propane-fueled heat source and a hydronic distribution system is applicable to many types of buildings from small homes to large commercial or

industrial facilities. This section discusses two examples of this combined technology.

Big Moose ResidenceThe first case study is a modest residence recently constructed in the Adirondack region of upstate New York (figure 8-1). The winters are harsh in this climate, and the owner wanted both comfort and fuel efficiency for his new home. Based on previous positive experiences with propane in combination with through-the-wall unit heaters, the owner approached the designer with a request for the same type of system. However, the designer raised a concern over the likelihood of cold concrete slab floors on the main level (even though the unit heater could maintain the proper air temperature within the

space). After considering this, the owner elected to use hydronic floor heating in both the slab-on-grade first floor areas, as well as the wood-framed second floor. With a hydronic-based system now in play, the designer encouraged extending its duties to include garage heating as well as domestic water heating. This allows a single compact propane-fueled boiler to handle all heating loads within the building.

A piping schematic of the system is shown in figure 8-2.

This home is very well insulated. All exterior wall cavities were filled with sprayed urethane foam insulation yielding a wall R-value of approximately 38. The ceiling is insulated with the same material to R-50. All slab areas were insulated on the underside and edges

with 2-inches of extruded polystyrene insulation. All windows have argon-filled double glazing with a low-E coating. The result is a 2,100 square foot home with a low design heat loss of approximately 22,000 Btu/hr. Garage heating adds approximately 16,300 Btu/hr making the total design heating load 38,300 Btu/hr.

A small wall-hung boiler with a output of 45,000 Btu/hr can easily handle this load. The boiler uses sealed-combustion with supply air and venting handled by 2-inch PVC (supply air), and 2-inch CPVC (venting) piping. This small diameter piping was easily routed from the second floor mechanical closet to just under the edge of the roof overhang. This eliminated the need to route piping or a conventional chimney through the metal roofing (which had no other piping or chimney penetrations). The end of the vent was located so it would not be damaged by frequent snow-slides from the roof.

First floor heating is handled by six circuits of 1/2-inch PEX-AL-PEX tubing embedded within the concrete slab as shown in figure 8-3 (next page). Although the entire first floor is operated as a single zone, room-by-room circuit layout enables the heat output to be adjusted through flow balancing.

Figure 8-1

Exterior of residence

Piping schematic for hydronic heating system

indirect water heater (prioritized load)

outdoor temp. sensor

propane-fired mod/con boiler

first floor heating circuits

second floor heating circuits

garage floor heating circuits

domestic hot water

Figure 8-2

Sec8:32

A tube-and-plate radiant panel heats the second floor. The same 1/2-inch PEX-AL-PEX tubing used in the first floor slab was installed on the underside of the second floor deck and supported by aluminum heat transfer plates, which were stapled in place as seen in figure 8-4. These plates and tubes are backed by a 6-inch layer of fiberglass insulation to force most of the heat output in the upward direction.

The garage is also heated by tubing embedded within the concrete floor slab, and operated as a separate zone. This enables the owner to maintain the garage at a reduced temperature without sacrificing comfort in occupied areas. It also allows the garage to be heated to full comfort temperature when used as a workshop during cold weather.

The entire hydronic system is filled with a non-toxic propylene glycol antifreeze solution. This protects the system against freezing in the event of an extended power outage. It also allows the garage to remain unheated if desired without concern of

freezing the hydronic floor circuits.

Domestic hot water is heated by a 40 gallon indirect water heater that’s operated as a priority load. When the tank requires heating all other loads are temporarily disabled to allow the full boiler output to quickly restore the tank to its setpoint temperature.

As soon as this occurs, the space heating circuits are allowed to operate. The high thermal mass of the radiant floor slab allows this process to go unnoticed. This strategy eliminates the need to size the boiler to the combined load of space heating and domestic water heating. The result is maximum domestic water heating, reduced cost, and improved seasonal efficiency. A photo of the installed mechanical closet is shown in figure 8-5.

The low operating temperature of the heated floors allows the mod/con boiler to operate at high efficiencies throughout the heating season to minimize propane consumption. Total projected propane usage to fully heat the house and garage in this cold Northern climate is 660 gallons per year.

In summary, this system provides unsurpassed comfort, compact installation, quiet operation, and high fuel efficiency.

Figure 8-4

Figure 8-5

Tubing layout for heated floor slab

vent

ed

propa

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ed

firep

lace

M. BEDROOM

LIVING

WD

CLOSET

M. BATH

1/2 BATH/ LAUNDRY

DINI

NG

coat

clo

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KITC

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GE

272+10=282 ft.

228+

10=2

38 f

t.

275+

10=2

85 f

t.

123+10=133 ft.

291+10=301 ft.

317+10=327 ft.

341+10=351ft.

Photo courtesy of Harvey Youker/ HYtech Heating

Mechanical closet showing wall-hung boiler and indirect water heater

Figure 8-3

Sec8:33

North Lake ResidenceAnother recently-constructed luxury home using propane-fueled hydronic heating is shown in figure 8-6.

This 5,000 square foot home includes 4 bedrooms and 3 bathrooms. It has a heated basement floor slab as well as tube-and-plate floor heating on the first and second floors. The latter are finished with a mixture of hardwood and ceramic tile. The hydronic system also provides domestic hot water for the home, and heats

the garage. Propane is also used for the fireplace, clothes dryer and kitchen stove.

Although this home is located in a climate where winter temperatures routinely drop to –20 ºF, total propane usage for all space heating,

garage heating, domestic hot water and appliances is approximately 800 gallons per year.

The use of tube-and-plate floor heating system, seen under construction in figure 8-8, allows a variety of floor coverings. The PEX-AL-PEX tubing is cradled by thin aluminum heat transfer plates that spread heat across the floor. This hardware is then covered by a thin layer of plywood to provide a smooth substrate for finish flooring. See finished results in Figure 8.9 (next page).

Prior to installation, the hydronics professional developed a tubing layout diagram for the entire system. This ensures the lengths of all circuits are acceptable, speeds the installation, and provides a permanent record of where all tubing is located.

The mechanical equipment is shown in figure 8-10 (next page). The propane-fueled mod/con boiler uses internal state-of-the-art controls to adjust the water temperature and heat output in response to outdoor temperature. The boiler also uses sealed combustion in which all combustion air is routed directly to the boiler through 3-inch PVC piping. All exhaust gases are vented outside through another 3-inch PVC pipe. The air supply and venting pipes can be seen at the top of the boiler.

Figure 8-6

Figure 8-7

Figure 8-8

Exterior of home. Courtesy of HYTech Heating

Ample hot water for this master bath comes from a propane-fueled boiler with indirect water heater. Courtesy of HYTech Heating

Tube-and-plate floor heating being installed. Courtesy of HYTech Heating

Sec8:34

The small circulators at the left of the boiler distribute heat to building zones precisely when and where it’s needed. The indirect domestic water heater tank at the far left is also heated by the boiler. This professionally installed system is compact and easily serviced. All space heating and domestic water heating is provided by a single highly efficient heat source, demonstrating the synergy of function and form that’s possible using propane in combination with hydronic heating.

Figure 8-10

The heated floors are finished in both hardwood and ceramic tile. Courtesy of HYTech Heating

Mechanical room with propane-fueled boiler, zone circulators, and indirect water heater. Courtesy of HYTech Heating

Figure 8-9

Sec9:35

Section 9: Cooling Options for Use with Hydronic Heating

Many discussions between comfort professionals and potential customers eventually move from heating to the inevitable question: “What do I do about cooling?”

The vast majority of new home buyers in all but the coldest regions of the United States expect their homes to be comfortable throughout the summer as well as in winter. Professionals who integrate cooling and heating in ways that provide year round comfort and efficiency are certainly well positioned for success. As you’re about to see, hydronics technology combined with propane can provide an elegant solution for cooling as well as heating.

There are several options for cooling buildings equipped with hydronic heating. Perhaps the most obvious is to install a separate central cooling system with traditional ducting. Although this has been done in many buildings, it often involves the complications associated with routing traditionally sized ducting throughout the building. It should not be dismissed as a possibility, but neither should it be accepted as unavoidable in light of alternatives to be discussed.

For the sake of discussion, we’ll categorize cooling options into non-hydronic and mixed “hydro-air” systems. The first category includes “ductless” cooling systems, as well as what are commonly known as direct expansion “miniduct” systems. The second category includes chilled water distribution systems supplied by either electrically powered compressor-based chillers, or propane-fueled absorption chillers.

Non-Hydronic Cooling OptionsAs previous sections have shown, a strength of hydronic heating is the ability to integrate the required hardware into almost any building with minimal disruption of structure or finish surfaces. When cooling is being planned these attributes are equally important, and often preclude the use of conventional ducting due to the size and routing requirements necessary for proper operation.

It is possible to provide zoned cooling without need of any ducting. The concept is shown in figure 9-1.

Ductless systems typically have wall-mounted indoor evaporator units in each cooling zone of the building. A refrigeration line set runs from each indoor evaporator unit to an outdoor condenser unit. In some cases a separate pad-mounted condenser unit is used for each indoor unit. In other cases two, three and even four independent condenser units are housed within a common outdoor unit.

The only connection between the outdoor condenser unit and the indoor evaporator unit is a refrigerant line set (flexible copper tubing) and electrical cabling. These relatively small tubes and cables can be routed through partitions and around other building structure much easier than ducting. Each indoor evaporator unit also requires a plastic pipe or hose to route condensate (water vapor condensed to liquid) to a suitable drain.

Ductless cooling provides the advantage of zoning. Each individual wall-hung unit can operate independently. From the standpoint of aesthetics, not everyone appreciates wall-mounted hardware in several rooms of the building. Some manufacturers offer flush-mounted ceiling units for these situations.

Mixed “Hydro-Air” Cooling Systems Over the last two decades, several North American companies have put forth cooling systems that rely on small (2-inch internal diameter) flexible ducting to distribute cool air to locations where conventional ducting simply won’t fit. To deliver sufficient cooling to a space, these small ducts must operate at higher flow velocities. This is achieved through the use of special high static pressure blowers in the air handling unit. A schematic of the concept is shown in figure 9-2. An example of a small air handler

air-cooled condensors

indoor evaporator & air handler

refrigeration piping

air-cooled condensor

insulated trunk duct

2-inch insulated

flex ducting

air handler

refrigerant piping

Figure 9-1

Figure 9-2

Concept of a “ductless” cooling system

Concept of a “miniduct” cooling system

Sec9:36

installed in the attic space of a home, and supplying several small flex ducts is shown in figure 9-3.

The cooling capacity for most miniduct systems is supplied from a refrigerant-based evaporator coil within the air handler. However, in some systems the cooling capacity is supplied using chilled water. The latter is a form of hydronics technology using cool water rather than heated water.

The concept of a hydronic homerun system for distributing chilled water to several independently controlled air handlers is shown in figure 9-4.

In this system, chilled water is “produced” by removing heat from water in the insulated storage tank. This is done using a standard direct expansion condenser unit connected to a flat plate heat exchanger. Liquid refrigerant is evaporated in one side of the flat plate heat exchanger. As the refrigerant within the heat exchanger changes from a liquid to a gas, it extracts heat from the water flowing through the other side of the heat exchanger. This chilled water is then routed back to the storage tank as warmer water moves into the heat exchanger for cooling. The process is controlled by monitoring the water temperature within the storage tank. A typical system maintains this water between 40ºF and 50ºF when the cooling system is active.

This hydronic distribution system uses small diameter PEX or PEX-AL-PEX tubing—the same tubing previous discussed for hydronic heating applications—to carry chilled water to each air handler. Another length of tubing returns warmed water from the air handler to the storage tank. Each air handler is controlled by a separate zone thermostat. Water

flow through the coil in each air handler is controlled by an electrically-operated zone valve.

One advantage of chilled water cooling is the elimination of larger ducting between a central air handler and the points where cool air is introduced to the building. Just as in heating, a flowing stream of water carries almost 3,500 times as much heat (or cooling effect) as an equivalent stream of air. This allows small tubing to convey the same cooling capacity as much larger ducting.

Another advantage of chilled water cooling is the relative ease of creating zones within a building. The basic concept is to locate a small chilled water air handler within each cooling zone of the building. That air handler operates only when cooling is needed in that zone. This reduces power consumption under part load conditions when not all zones are active. It also greatly improves comfort by delivering cooling precisely when and where it’s needed. Finally, the controls needed to extensively zone a chilled water cooling system are far less complicated and less costly than those needed to properly regulate a zoned forced air system.

air handlersw/ chilled water coils

1" c

oppe

r (in

sula

ted

with

clo

sed-

cell

foam

)

5/8"PEX-AL-PEX

tubing(insulated w/

closed-cell foam)

zonevalves

air-cooled condensorinsulated

chilled waterstorage tank

refrigerantpipine

INSIDE OUTSIDE

temperaturecontroller

insulated trunk duct

2-inch diameterinsulated flex ducting

ceilingdiffuser

Figure 9-3

Figure 9-4

Small air handler located in attic supplies several miniducts

Use of hydronic distribution system to deliver chilled water to zoned air handlers

Sec9:37

When installing a chilled water cooling system, it’s crucial that all piping and piping components carrying chilled water are insulated, and subsequently vapor sealed. Not doing so allows water vapor in the surrounding air to condense on the piping. This can quickly lead to dripping that can stain ceilings and, over time, create mold within the building.

Chilled Water Using a Propane-Fueled Absorption ChillerAlthough lesser known, there is a well-establish technology for using heat from a combustion process to produce chilled water. That process is called absorption cooling, and it’s been used in larger buildings for several decades. Recently, this technology has been scaled down for use in residential and small commercial buildings. Propane is an ideal energy source to power a small absorption chiller.

Unlike conventional cooling equipment, absorption chillers do not use a motor-driven compressor. Instead they rely on a cycle in which ammonia, hydrogen gas, and water are used to generate chilled water. This process requires heat from a gas burner to sustain it. The heat extracted from the water flowing through the absorption chiller as well as the heat generated by the gas burner are eventually rejected to outside air.

An example of a residential size propane-fueled absorption chiller is shown in figure 9-5.

Water cooled by an absorption chiller can be stored in the same type of insulated storage tank previously described for a compressor type chiller. This water can be distributed to remote air handlers through the same type of hydronic distribution system.

Modern propane-fueled absorption chillers use up to 87 percent less electrical energy than a standard compressor driven chiller.

They have very few moving parts and thus require little maintenance. Although more expensive to install than standard chillers, they typically last two to three times longer and thus provide comparable, if not favorable, economics. They add very little to peak summer electrical demands. Some companies even offer variants on standard absorption chillers that supply both chilled and heated water when needed at the same time. In combination with propane and a hydronic delivery system, absorption chillers represent a state-of-the-art cooling option for residential and commercial applications.

SummaryThere are several ways cooling can be integrated along with propane-fueled hydronic heating to provide year round comfort. The use of chilled water to convey the cooling throughout a building holds many advantages over forced air distribution. The chilled water can be produced using standard compressor driven chillers or through modern propane-fueled absorption chillers.

Figure 9-5

A small propane-fueled absorption chiller for residential cooling

Sec10:38

Section 10: Additional Sources of Information

Hydronics Technology1. Publications: a. Plumbing & Mechanical magazine www.pmmag.com b. PM Engineer magazine www.pmengineer.com c. Contractor magazine www.contractormag.com d. Radiant Living magazine www.radiantlivingmag.com

2. Associations: a. Radiant Panel Association

www.radiantpanelassociation.com b. Hydronics Industry Alliance

www.myhomeheating.com c. Hydronic Heating Association

www.comfortableheat.net d. Plumbing-Heating-Cooling Contractors Association

www.phccweb.org

3. Other hydronic heating Websites: a. www.hydronicpros.com b. www.heatinghelp.com c. www.healthyheating.com d. www.radiantandhydronics.com

4. Technical Reference Books: a. Modern Hydronic Heating: For Residential & Light

Commercial Buildings, 2nd Edition, ISBN 0-7668-1637-0

b. Radiant Basics: A Basic Course for Radiant Panel Heating Systems ISBN 1-932137-00-9. Published by the Radiant Panel Association

c. Guide 2000 Residential Hydronic Heating –

Installation and Design Training manual published by the Gas Appliance Manufacturers Association

Propanea. Propane Education and Research Council (PERC)

www.propanecouncil.orgb. Gas Appliance Manufacturers Association

www.gamanet.orgc. BuildwithPropane.comd. Find a Propane Retailer www.usepropane.com/find/

Contributors’ DirectoryListing of companies and individuals contributing graphics to the publication

Bradford White www.bradfordwhite.comCaleffi North America www.caleffi.comECR International www.ecrinternational.comGastite Corporation www.gastite.comGenerac Power Systems, Inc. www.generac.comHeatlines, Inc www.heatlines.comIPEX Corporation www.ipexinc.comLochinvar Corporation www.lochinvar.comMarathon Engine Systems www.marathonengine.comMonitor Products, Inc. www.monitorproducts.comMyson Incorporated www.mysoninc.comRinnai America Corporation www.rinnai.usRobur www.robur.comTriangle Tube www.triangletube.comVasco www.theheatingcompany.comWebstone Company, Inc. www.webstonevalves.comWeil-McLain www.weil-mclain.com

Heating ProfessionalsDan Foley www.southjerseyoilheat.com/foley.htmlGary Todd Televisual Productions, Greensboro, NC phone 336-643-1221Harvey Youker www.hytechheating.comLarry Drake www.radiantpanelassociation.comPaul Rohrs www.biggerstaffradiantsolutions.com

For more informationContact:Tracy BurlesonDirector, Residential Trade Outreach and PartnershipsPERCtracy.burleson@propanecouncil.org