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What is a Heat Pump and how does it work?

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Heat pump

A heat pump represents a growing segment of the HVAC industry. In practical terms, it is a reversal of how the air conditioning system works. While air conditioners are used to cool air; a heat pump can be used to cool or heat the air. This is especially true conditions are in place for this use. Therefore, it is necessary to employ a heat pump where temperatures are more moderate. The Summer months of the mid-south area of the United States contains the ideal  conditions for this type of system. Conversely, they can be converted into a heating application when the temps are a bit cooler. In areas such as Florida or California where temperatures are mostly warm, it is best to use an air conditioner only.

The Heat Pump Refrigeration Cycle

Heat pumps use a reverse refrigeration cycle as opposed to the regular vapor compression cycle of an ac unit. Heat pumps use the condenser section to generate heat whereas an air conditioner uses it to reject heat. A heat pump uses a small amount of energy to move heat from one location to another. In a similar way it can cool a building or office space by working in reverse.

Air conditioners and heat pumps work in a very similar way. The biggest advantage to a heat pump is to negate the unit handling the separate loads of heating and cooling. Since the heat pump is only transferring heat it can operate by electricity. Additionally, the unit does not rely on the burning of fuel to accomplish the process.

In the cooler months, a reversing valve reroutes the refrigerant path making the outdoor condensing coil function as the evaporator. In a likewise manner the indoor coil serves as the condenser. The evaporator absorbs the outdoor heat and is in turn used by the condenser to heat the indoor space. However, there is one remaining problem. The outdoor evaporator absorbs heat and must operate at temperatures lower than the outside air. This low operating temperature causes ice to build-up on the outside of the evaporator. Finally, auxiliary heat is used during the defrost cycle to provide indoor heat during this stage.