hydronic water heat, components & variables 12-16 · boilers are similar to high efficiency...

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The Journal Light Construction issues November 1997 & 1998, & April 1999

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The Home Inspection Company, Inc. DBA Professional Home Inspection Company

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Hydronic Hot Water Heat Components & Variables

Newer hydronic heat technologies and components have improved efficiencies. For example condensing boilers are similar to high efficiency furnaces. Both produce moisture when extracting high amounts of energy

from the burning of natural gas or propane. This high extraction of energy will lower the exhaust gas temperature thus allowing the use PVC flue materials similar to a high efficient furnace. When oil is used as a fuel source, it produces less moisture so condensing boilers are less applicable. When hydronic heat is used

for radiant heat under concrete slabs, it will require lower water temperatures. A water heater, because it operates at lower temperatures, is sometimes substituted for a boiler. Depending on the size and efficiency of the water heater and the overall size of the concrete slab being heated, a water heater may be less suitable for the application. When a boiler is used to heat concrete slabs, it often uses mixing valves to lower the operating

water temperature to accommodate the concrete slab.

When selecting an HVAC company to clean and inspect your hydronic heating system always check references and ask questions. Base your decision in part on this newsletter. To learn the most about

your system, we recommend you attend the entire inspection/review.

Basics There are many components to a basic system. Most of the components operate with little sound/movement:

• The Boiler: (may be a condensing, non-condensing or a water heater) � Flame Color: A natural gas or propane fueled boiler should have a blue flame. A flame with

yellow streaks indicates debris buildup in the burners or a lack of air. Oil burner flame is generally yellow/orange in color.

� Signs of Moisture: Areas around the boiler and pipe connections or fittings displaying active leakage or past staining suggests a lack of maintenance. Any active leakage or an unexplained sign of moisture is a concern.

• Expansion / Compression Tank: � Plain Steel Expansion Tanks (larger)-often hang from floor rafters: Heated internal boiler water

will give off air. The “Air Separator” will catch the air and deposit it into the tank. As the system cools, the air is absorbed back in to the water

� Diaphragm-Type Tanks (smaller)-installed/supported on boiler piping: These contain a flexible diaphragm that separates the air and water in the tank. The tank is pre-charged with air. Heated water enters the tank; the internal diaphragm flexes to accommodate the hot water. When the water cools, the diaphragm pushes the water back into the system.

• Back Flow Preventer: Prevents potable house water which enters the system from returning to potable house supply side. It is basically a one way check valve.

• Pressure Reducing Valve: Reduces potable water pressure (40-70psi) to system pressure (10-20+/-psi)

• System Pump: An inline pump (often on the return side of the piping) that pulls water thru the system.

• Zoning: Zoning valves allows isolation-turning off rooms/sections of a home not in use. Efficiency of individual zones is enhanced by zoning pumps which will boost water movement and heat transfer in each unique zone.

• Flow Check Valve: A valve that only allows water to flow one direction, typically separating the potable (drinking) water from the system (non-drinking) water.

• Air Purger: Catches the air in the flowing water and deposits it into the large steel tank.

• Flue: A pipe (metal or PVC) used to route the combustion exhaust gases to the outside. Some flues incorporate an electronic damper that will close the flue when the boiler is not operating, and thus improve efficiency.

• System Piping: Solid copper or flexible plastic (PEX) type piping that is used to route heated water to individual radiators.

• Relief Valve: A spring loaded valve that opens to release heated water when internal system pressures exceed design limitations. There are many reasons (lack of maintenance, part(s) failure etc.) that can cause this to occur. If water is exiting the metal relief valve piping, service is recommended. Testing and service of the relief valve setup is best left to the HVAC professional.

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Considerations

• Maintenance Costs: Hydronic heating systems use water as the means of heat transfer. Because water is messier and thus requires more time and materials to handle, the repair process can be more expensive. Hydronic heat has few moving parts. The properly operating system will typically be very quiet. Any unusual noises such as percolation noises, or a pump becoming increasingly louder may indicate internal blockages and wear/tear suggesting the need for routine maintenance or repairs. It is a good idea to familiarize yourself with normal day to day operational noises. When unusual items/noises are noted and addressed in a timely fashion, repairs costs may be less.

• Radiant Heat: Radiant heat is produced by heating a material such as concrete. Heated concrete in turn radiates this heat to other areas, people, furniture, building materials that come into contact with it. Radiant heat is a very efficient form of heating. It is also very slow to raise the surrounding temperature.

• Convective Heat: Convective heat can take place in a heat exchanger mounted in ductwork, or by a radiator installed along the bottom of exterior walls. The radiator, since it is next to the floor, will be surrounded by heavy cool air. When hot water is pumped through the radiator, small fins attached to the hot pipe greatly increase the surface area of the hot pipe. This greater surface area will in turn heat the surrounding cooler air. When this lower cooler air is heated, it rises up. The rising warm air will cause more cool lower air to be pulled into the warm environment of the fins creating a circular heating path of air through the radiator. It is very important to not obstruct radiators with furniture, drapes, etc.

• Radiant / Convective combo systems: Homes that incorporate radiant floor heat and convective forced air furnace type heat are typically very efficient due to their duel methods of heat production. A forced air furnace has the added benefit of heating, drying and filtering the air and thus reducing airborne (dust) contaminant, virus and bacteria exposures.

• Water Quality: Boilers operate in a closed system. A properly maintained boiler’s closed system does not require extra water from the home’s plumbing system because it repeatedly heats the same internal system water. It is common for city and well water to be hard. Hard water contains calcium and magnesium which will leave scale like residues on fixtures, toilets and sinks. When, hard water is heated, these deposits will cause internal lime buildup. Lime will obstruct a boiler’s heat exchanger, piping, tanks, and radiators. Lime deposits also form inside water heaters. A water softener will reduce lime and scale buildups and thus improve long-term functionality. Well water also may contain other elements such as high iron, contaminants and gases that will also affect boilers and water heater long-term operations.

Need More Information?

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hydronic water heat, components & variables 12-16 · boilers are similar to high efficiency...

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