how heat pumps work
Air source heat pumps are just like regular air conditioners except they have a reversing valve on the system that allows the freon (refrigerant in the system) to either flow in a path for heating or a path for cooling. Most heat pumps are split style systems with an air handler and evaporator (indoor coil) indoors, and compressor and condenser (outdoor coil) outdoors. Package style systems have the same components usually on the roof outside in a big metal box (cabinet) if your in the Phoenix Metropolitan.

Both coils are made of copper tubing with aluminum fins to help with heat transfer, fans blow air through these coils and the cooled or heated air goes through the duct system supplying you with conditioned air. The compressor forces the refrigerant through a circuit of coils and pipes.


In cooling mode the outdoor coil (condenser) releases collected heat in the freon (refrigerant) to outside and keeps cold air inside at the indoor coil (evaporator). Air blows over the indoor coil and distributes cold air throughout the duct system keeping your home cool.


When in heating mode the outdoor air is cooled (refrigerated with freon) to remove some of its heat. The freon (the refrigerant in the system) brings the heat to the indoor coil where the heat is distributed through the duct system by fans blowing air over the coil.


The energy rating of air conditioners is the seasonal energy efficiency ratio thats based on how many BTU’s or heat the unit can remove outdoors for each watt of power it draws when cooling. The seasonal energy efficiency ratio is the efficiency rating of air conditioners or a heat pump when its cooling.

A heat pumps efficiency can be rated in a number of ways though. The most common and oldest method of rating is the coefficient of performance or COP. COP tells you how many times more efficient a heat pump is to electric resistance. Heating COP’s range from 1.5 to 4, depending on climate, design and installation.

A newer heating efficiency called the heating seasonal performance factor or HSPF that is listed on the energy guide label of every heat pump in the united states. HSPF includes both the very efficient heating done by the compressor and the less efficient heating done by electric resistance heaters (heat strips) that can be on a heat pump. The HSPF gives you the amount of BTU’s the heat pump can deliver indoors for each watt of electricity it uses.


Krigger, John, and Chris Dorsi. “Chapter 6 Heating.” Residential Energy: Cost Savings and Comfort for Existing Buildings. Ed. Mary Coster and Margaret Regan. 5th ed. Helena, MT: Saturn Resource Management, 2009. 177-79. Print.

Krigger, John, Chris Dorsi, and Margaret Regan. “Chapter 8 Cooling.”Residential Energy: Cost Savings and Comfort for Existing Buildings. Ed. Mary Coster. 5th ed. Helena, MT: Saturn Resource Management, 2009. 208-10. Print.

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