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Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber,...
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Transcript of Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber,...
![Page 1: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/1.jpg)
Air-Source Heat Pumps INorth Seattle Community College HVAC Program
Instructor – Mark T. Weber, M.Ed.
Airsource Heat Pump 1
![Page 2: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/2.jpg)
Objectives
• After studying this unit, you should be able to: – Describe a reverse-cycle heat pump– List the components of a reverse-cycle
heat pump– Explain a reversing valve (4-way valve)– State the various heat sources for heat
pumps
![Page 3: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/3.jpg)
Objectives (cont’d.)
– Compare electric heat to heat with a heat pump
– State how heat pump efficiency is rated– Determine by the line temperatures
whether a heat pump is in cooling or heating
– Discuss the terminology of heat pump components
![Page 4: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/4.jpg)
Objectives (cont’d.)
– Define coefficient of performance– Explain auxiliary heat– Describe the control sequence on an air-to-
air heat pump– Describe techniques being used to improve
the efficiency of heat pump systems– Discuss recommended preventive
maintenance procedures for heat pump systems
![Page 5: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/5.jpg)
Reverse-Cycle Refrigeration
• Air-conditioning equipment can only pump heat in one direction
• Heat pumps can pump heat two ways – Also have a four-way reversing valve– Four-way reversing valves control the
direction of flow of the heat-laden vapor between the low- and high-pressure sides of the system
![Page 6: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/6.jpg)
Heat Sources For Winter
• Air conditioners pump heat from low temperature inside the structure to a higher temperature outside the house
• At 0°F outside air temperature, there is still usable heat in the air
• The heat pump removes heat from the outside air in the winter and deposits it in the conditioned space to heat it
![Page 7: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/7.jpg)
Heat Sources For Winter (cont’d.)
An air-to-air heat pump removing heat from 0°F air and depositing it in a structure for winter heat
![Page 8: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/8.jpg)
The Reversing Valve
• Allows the heat pump to pump heat in two directions
• Diverts the discharge gas to either heat or cool the conditioned space
• Refrigerant is directed from the compressor to the indoor coil in the heating mode
![Page 9: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/9.jpg)
• Refrigerant is directed from the compressor to the outdoor unit in the cooling mode
• Controlled by the space temperature thermostat
• Pilot-operated valve
• Four piping connections on the valve
![Page 10: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/10.jpg)
An air-to-air heat pump moving heat from the inside of a structure to the outside
![Page 11: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/11.jpg)
In the winter, the heat pump moves heat into the structure
![Page 12: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/12.jpg)
Internal slide in the four-way reversing valve. The solenoid determines the position of the slide. Most systems operate in the heating mode when the solenoid is de-energized. (A) Position of the slide when the solenoid is de-energized. (B) Position of the slide when the solenoid is energized
![Page 13: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/13.jpg)
Types of Heat Pumps
• Air is not the only source from which a heat pump can absorb heat– Other heat sources for heat pumps include
water, earth, and solar– A typical water-to-air heat pump uses 3
gallons of water per minute in the heating cycle and 1.5 gallons of water per minute in the cooling mode per ton of refrigeration
![Page 14: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/14.jpg)
The Air-to-Air Heat Pump • Most popular type
• Basic sealed system components of a heat pump are the same as an air conditioner, but the terminology changes
• In a heat pump, the terms indoor coil and outdoor coil are used
• The function of each coil changes as the operating mode of the heat pump changes
![Page 15: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/15.jpg)
The Air-to-Air Heat Pump (cont’d.)
• Function of coils in the heating mode– Outdoor coil absorbs heat by boiling
refrigerant at low temperature and pressure (evaporator)
– Indoor coil rejects heat by condensing it to a high-temperature and pressure vapor (condenser)
– Hot gas from the compressor is first pumped to the indoor coil
![Page 16: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/16.jpg)
The Air-to-Air Heat Pump (cont’d.)
• Function of coils in the cooling mode – Indoor coil absorbs heat by boiling refrigerant
at low temperature and pressure (evaporator)– Outdoor coil rejects heat by condensing it to a
high-temperature and pressure vapor (condenser)
– Refrigerant from the compressor is first pumped to the outdoor coil
![Page 17: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/17.jpg)
The Air-to-Air Heat Pump (cont’d.)
• Mode of operation is determined by which way the hot gas from the compressor is flowing
• Mode of operation can be determined by touching the gas (suction) line to the indoor coil – In the cooling mode, the gas line will feel cool – In the heating mode, the gas line will feel hot
![Page 18: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/18.jpg)
Refrigerant Line Identification
• The larger diameter line is called the gas, vapor or suction line because only refrigerant vapor flows through it
• The gas line is a cold gas line in the summer and a hot gas line in the winter
![Page 19: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/19.jpg)
Refrigerant Line Identification (cont’d.)
• The smaller diameter line is called the liquid line because only liquid refrigerant travels through it
• During the cooling mode, the liquid travels to the indoor coil
• During the heating mode, the liquid travels to the outdoor coil
![Page 20: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/20.jpg)
Refrigerant Line Identification (cont’d.)
This split-system heat pump shows the interconnecting refrigerant lines
![Page 21: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/21.jpg)
Metering Devices
• Specially designed for heat pump applications
• There must be a metering device at the outdoor unit in the heating mode
• There must be a metering device at the indoor coil in the cooling mode
![Page 22: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/22.jpg)
Thermostatic Expansion Valves
• Maintains desired superheat in the evaporator
• Check valves are piped parallel to the TXV to allow refrigerant to bypass the control when needed
![Page 23: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/23.jpg)
Thermostatic Expansion Valves (cont’d.)
• Heating mode– The refrigerant flows through the TXV at
the outdoor coil– The refrigerant bypasses the TXV at the
indoor coil
![Page 24: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/24.jpg)
Thermostatic Expansion Valves (cont’d.)
• Cooling mode – The refrigerant flows through the TXV at
the indoor coil– The refrigerant bypasses the TXV at the
outdoor coil
![Page 25: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/25.jpg)
Thermostatic Expansion Valves (cont’d.)
In the heating mode, hot gas from the compressor flows through the indoor coil and through the open check valve to bypass the indoor metering device. (B) In the cooling mode, high-pressure liquid refrigerant is directed through the metering device because the check valve will be in the closed position
![Page 26: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/26.jpg)
Electronic Expansion Devices
• Can meter refrigerant in both directions
• If indoor and outdoor coils are close together, one device can be used
• The correct superheat will be maintained in both heating and cooling modes
![Page 27: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/27.jpg)
Orifice Metering Devices
• Used in conjunction with check valves
• One device is located at each coil
• The bore at the indoor coil is larger than the bore at the outdoor coil
• Normally used with a bi-flow filter drier
![Page 28: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/28.jpg)
Liquid Line Accessories
• Two standard filter driers can be used on systems with check valves– Only one drier in the circuit at a time– They are installed with the arrows pointing
in the same direction as the check valves
• Bi-flow filter driers– Two driers in one– Designed for heat pump applications
![Page 29: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/29.jpg)
Liquid Line Accessories (cont’d.)
In the heating mode, the cooling metering device is bypassed
![Page 30: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/30.jpg)
Liquid Line Accessories (cont’d.)
In the cooling mode, the heating metering device is bypassed
![Page 31: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/31.jpg)
Application of the Air-to-Air Heat Pump
• Usually installed in milder climates– In winter, the outdoor coil absorbs heat
• If outside temperature is 10°– Refrigerant boils at approximately -15°
• Compressor and the system lose efficiency as the evaporator temperature drops
• The system loses capacity as the outside temperature drops
![Page 32: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/32.jpg)
Auxiliary Heat
• Required when the heat pump cannot provide all the heat a structure needs– The heat pump is the primary heat source– Auxiliary heat could be electric, oil or gas– Electric heat is the most common auxiliary
heat used – As the outside temperature drops, the
structure requires more heat
![Page 33: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/33.jpg)
Balance Point
• Balance point occurs when the heat pump can pump in exactly as much heat as the structure is leaking out
• Above the balance point, the heat pump will cycle on and off
• Below the balance point, the heat pump will run continuously and second stage (auxiliary) heat will be energized
![Page 34: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/34.jpg)
Coefficient of Performance
• One watt of usable heat is supplied for each watt of energy purchased – 100% efficient
• Coefficient of performance (COP) of 1:1• The output is the same as the input
• Air-to-air heat pumps: a COP of 3.5:1– One watt of electrical energy used by the
compressor can furnish 3.5 watts of usable heat
![Page 35: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/35.jpg)
Coefficient of Performance (cont’d.)
• High COP only occurs during higher outdoor winter temperatures
• A heat pump’s COP falls as the outdoor temperature falls
• A typical air-to-air heat pump has a COP of 1.5:1 at 0°F
![Page 36: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/36.jpg)
Coefficient of Performance (cont’d.)
• Some manufacturers have controls to shut off the compressor at temperatures of 0 to 10°F
• Water-to-air heat pumps might not need auxiliary heat since the heat source (water) temperature is constant
• Water-to-air heat pumps have a COP rating as high as 5:1
![Page 37: Air-Source Heat Pumps I North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. Airsource Heat Pump 1.](https://reader035.fdocuments.net/reader035/viewer/2022062421/56649e0f5503460f94afa198/html5/thumbnails/37.jpg)
For more information please contactMark T. Weber
At North Seattle Community College