1 hvacr216 - hydronics heat sources. 2 classification of hydronic heat sources conventional gas and...

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HVACR216 - HydronicsHVACR216 - Hydronics

Heat SourcesHeat Sources

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Classification of Hydronic heat sourcesClassification of Hydronic heat sources

• Conventional gas and oil fired boilers

• Condensing gas fired boilers

• Electric resistance boilers

• Electric thermal storage equipment

• Hydronic heat pumps

• Renewable energy heat sources

• Conventional gas and oil fired boilers

• Condensing gas fired boilers

• Electric resistance boilers

• Electric thermal storage equipment

• Hydronic heat pumps

• Renewable energy heat sources

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Heat sourcesHeat sources

• Of these, conventional gas and oil boilers are currently being used in the vast majority of residential and light commercial hydronic systems in the USA.

• Of these, conventional gas and oil boilers are currently being used in the vast majority of residential and light commercial hydronic systems in the USA.

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Gas and Oil fired designsGas and Oil fired designs

• Most boilers that operate on natural gas or fuel oil can be classified according to their physical construction and heat exchanger material.

• Most boilers that operate on natural gas or fuel oil can be classified according to their physical construction and heat exchanger material.

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Cast Iron Sectional BoilersCast Iron Sectional Boilers

• The cast-iron sectional boiler is currently the most common type of boiler used in residential and light commercial buildings in North America.

• The cast-iron sectional boiler is currently the most common type of boiler used in residential and light commercial buildings in North America.

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Four section boiler

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• Since the water flows completely around the heat source, these types of boilers are called Wet Base boilers.

• The wet base boiler is the common configuration for oil fired boilers.

• Since the water flows completely around the heat source, these types of boilers are called Wet Base boilers.

• The wet base boiler is the common configuration for oil fired boilers.

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• In this type of boiler, water is heated in cast iron chambers called sections.

• The sections are bolted together to form a boiler block.

• The hot gases generated in the combustion chamber near the bottom of the boiler rise up through the cavities between the sections and transfers the heat to the water within.

• In this type of boiler, water is heated in cast iron chambers called sections.

• The sections are bolted together to form a boiler block.

• The hot gases generated in the combustion chamber near the bottom of the boiler rise up through the cavities between the sections and transfers the heat to the water within.

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• The greater the number of sections, the greater the heat output of the boiler.

• Most cast iron sectional boilers for residential and light commercial applications are sold as packaged boilers.

• The greater the number of sections, the greater the heat output of the boiler.

• Most cast iron sectional boilers for residential and light commercial applications are sold as packaged boilers.

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• This implies that components such as the circulator, burner and controls are selected and mounted on the boiler by the manufacturer.

• The components supplied by the manufacturer assume the boiler will be used in a typical residential system.

• In some cases one or more of these components may not be best for a specific application.

• This implies that components such as the circulator, burner and controls are selected and mounted on the boiler by the manufacturer.

• The components supplied by the manufacturer assume the boiler will be used in a typical residential system.

• In some cases one or more of these components may not be best for a specific application.

12Packaged boilerPackaged boiler

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• The amount of metal in cast iron section boilers makes them relatively heavy.

• Even small cast iron boilers can weigh as much as 300 to 400 pounds.

• Such boilers typically contain 10 – 15 gallons of water.

• The amount of metal in cast iron section boilers makes them relatively heavy.

• Even small cast iron boilers can weigh as much as 300 to 400 pounds.

• Such boilers typically contain 10 – 15 gallons of water.

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Wear a back support brace and ask for additional help when lifting, moving, loading, or unloading these heavy boilers.

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• The combination of metal and water weight gives cast iron boilers the ability to absorb a significant amount of thermal energy.

• Such boilers are said to have a high thermal mass.

• These boilers are known as high mass boilers

• The combination of metal and water weight gives cast iron boilers the ability to absorb a significant amount of thermal energy.

• Such boilers are said to have a high thermal mass.

• These boilers are known as high mass boilers

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• A well insulated boiler housing, or jacket as it is commonly called, reduces standby heat loss from the boiler.

• A well insulated boiler housing, or jacket as it is commonly called, reduces standby heat loss from the boiler.

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Cleaning Cast Iron Sectional BoilersCleaning Cast Iron Sectional Boilers

• Some manufactures design the cast iron boilers for vertical passage of the flue gasses.

• To clean these types of boilers, the sheet metal top panel, flue connection and flue gas collector assembly must be removed before a cleaning brush can be maneuvered between the sections.

• Some manufactures design the cast iron boilers for vertical passage of the flue gasses.

• To clean these types of boilers, the sheet metal top panel, flue connection and flue gas collector assembly must be removed before a cleaning brush can be maneuvered between the sections.

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• Another type of cast iron boiler design uses horizontal passages between the sections with a hinged door to access both the combustion chamber and the flue gas passages.

• Another type of cast iron boiler design uses horizontal passages between the sections with a hinged door to access both the combustion chamber and the flue gas passages.

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Steel Fire Tube BoilersSteel Fire Tube Boilers

• Besides cast iron, steel has been used in the construction of boilers for decades.

• In a steel Fire Tube boiler, water surrounds a group of steel tubes through which the hot combustion gasses pass.

• Besides cast iron, steel has been used in the construction of boilers for decades.

• In a steel Fire Tube boiler, water surrounds a group of steel tubes through which the hot combustion gasses pass.

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• Spiral shaped baffles known as turbulators are inserted into the fire tubes to increase heat transfer by inducing turbulence and slowing the passage of the exhaust.

• The fire tubes are welded to steel bulkheads at each end to form the overall heat exchanger assembly.

• Spiral shaped baffles known as turbulators are inserted into the fire tubes to increase heat transfer by inducing turbulence and slowing the passage of the exhaust.

• The fire tubes are welded to steel bulkheads at each end to form the overall heat exchanger assembly.

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• Although steel fire tube boilers generally have less mass (metal weight) than cast iron boilers of similar capacity, they often hold more water.

• A typical steel fire tube boiler contains between 15-30 gallons of water.

• Although steel fire tube boilers generally have less mass (metal weight) than cast iron boilers of similar capacity, they often hold more water.

• A typical steel fire tube boiler contains between 15-30 gallons of water.

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Steel Fire Tube BoilerSteel Fire Tube Boiler

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Copper Water Tube BoilersCopper Water Tube Boilers

• Some boilers use water filled copper tubes as their heat exchanger.

• These also come in vertical and horizontal tube arrangements.

• Copper tubes are usually manufactured with fins that greatly increase the are exposed to the flue gasses for improved heat transfer.

• Some boilers use water filled copper tubes as their heat exchanger.

• These also come in vertical and horizontal tube arrangements.

• Copper tubes are usually manufactured with fins that greatly increase the are exposed to the flue gasses for improved heat transfer.

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Copper Water Tube BoilersCopper Water Tube Boilers

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Combined boiler /domestic water tank assembliesCombined boiler /domestic water tank assemblies

• A large percentage of residential hydronic systems supply both space heating and domestic hot water.

• Although several methods have been used to provide domestic hot water from a space heating boiler, it is generally accepted that the most efficient approach uses a storage tank that is indirectly heated by the boiler.

• A large percentage of residential hydronic systems supply both space heating and domestic hot water.

• Although several methods have been used to provide domestic hot water from a space heating boiler, it is generally accepted that the most efficient approach uses a storage tank that is indirectly heated by the boiler.

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Boiler with an indirect fired water heaterBoiler with an indirect fired water heater

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Combined boiler /domestic hot water assembliesCombined boiler /domestic hot water assemblies

• Several manufactures now offer products that combine a boiler and hot water storage into a single unit.

• Several manufactures now offer products that combine a boiler and hot water storage into a single unit.

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Combination unitCombination unit

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Dry Base BoilersDry Base Boilers

• Another common configuration is called the Dry Base Boiler.

• These boilers suspend the water filled heat exchanger above the combustion chamber

• Another common configuration is called the Dry Base Boiler.

• These boilers suspend the water filled heat exchanger above the combustion chamber

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Dry Base BoilersDry Base Boilers

• Gas fired cast iron boilers and oil fired vertical tube boilers are typically designed as dry base boilers.

• Gas fired cast iron boilers and oil fired vertical tube boilers are typically designed as dry base boilers.

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Cast Iron BoilersCast Iron Boilers

• All the boilers listed above (except the combo unit) are classified as conventional boilers.

• Conventional boilers usually operate with a maximum efficiency of 85%

• Conventional boilers are designed to operate with a hot enough exhaust temperature so that the byproduct of combustion (water vapor) will not condense back into a liquid.

• All the boilers listed above (except the combo unit) are classified as conventional boilers.

• Conventional boilers usually operate with a maximum efficiency of 85%

• Conventional boilers are designed to operate with a hot enough exhaust temperature so that the byproduct of combustion (water vapor) will not condense back into a liquid.

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Cast Iron BoilersCast Iron Boilers

• If the exhaust temperature were to be lowered and the water vapor were to reach its dew point, other byproducts of combustion would be entrained in this fluid and would create a very caustic environment for the cast iron or steel the unit is made out of.

• If the exhaust temperature were to be lowered and the water vapor were to reach its dew point, other byproducts of combustion would be entrained in this fluid and would create a very caustic environment for the cast iron or steel the unit is made out of.

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CondensateCondensate

• A good analogy to flue gas condensation in a boiler is seen in the exhaust from a car on a cool day.

• When the car is first started, the temperature of the exhaust pipe and muffler is low enough to cause some of the water vapor produced in the engine to condense by the time it reaches the tailpipe.

• A good analogy to flue gas condensation in a boiler is seen in the exhaust from a car on a cool day.

• When the car is first started, the temperature of the exhaust pipe and muffler is low enough to cause some of the water vapor produced in the engine to condense by the time it reaches the tailpipe.

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CondensateCondensate

• Water can often be seen dripping from the tailpipe when the car is first started.

• After the tail pipe warms above the dew point temperature, the water vapor no longer condenses, and the dripping stops.

• Water can often be seen dripping from the tailpipe when the car is first started.

• After the tail pipe warms above the dew point temperature, the water vapor no longer condenses, and the dripping stops.

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Condensing BoilersCondensing Boilers

• After the energy crisis of the 1970s, higher fuel costs motivated boiler manufacturers to research methods for improving boiler efficiency.

• Analysis by engineers and scientists found that significant amount of heat can be recaptured from the exhaust stream if the water vapor it contains can be condensed within the boiler.

• After the energy crisis of the 1970s, higher fuel costs motivated boiler manufacturers to research methods for improving boiler efficiency.

• Analysis by engineers and scientists found that significant amount of heat can be recaptured from the exhaust stream if the water vapor it contains can be condensed within the boiler.

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Condensing BoilersCondensing Boilers

• Condensing boilers are designed with large heat exchanger surfaces to extract more heat from the exhaust gasses compared to conventional boilers.

• These heat exchangers are made out of stainless steel or some kind of protected metal to resist corrosion.

• Condensing boilers are designed with large heat exchanger surfaces to extract more heat from the exhaust gasses compared to conventional boilers.

• These heat exchangers are made out of stainless steel or some kind of protected metal to resist corrosion.

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Condensing boilerCondensing boiler

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• Currently available boilers use high grade stainless steel or proprietary electroplated coatings to effectively eliminate corrosion.

• Condensing boilers are more expensive than conventional boilers of equal capacity.

• Currently available boilers use high grade stainless steel or proprietary electroplated coatings to effectively eliminate corrosion.

• Condensing boilers are more expensive than conventional boilers of equal capacity.

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• Condensing boilers that are designed and installed properly, will achieve much more efficiency than conventional boilers.

• When designed and installed properly these types of boilers can obtain 95+ % efficiency.

• Condensing boilers that are designed and installed properly, will achieve much more efficiency than conventional boilers.

• When designed and installed properly these types of boilers can obtain 95+ % efficiency.

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