Charging a residential heat pump is not a job for the average do-it-yourselfer. In fact, it should only be carried out by someone who has been certified by the EPA, and is a professional. If you'll be having this work done at your home, however, it's good to understand the basic process.

HVAC heating and air conditioning units
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How to Charge a Residential Heat Pump

Heat Pump Basics

A heat pump uses the air outside your home to heat it in the wintertime and cool it in the summertime. Usually, there is a device that looks like an air conditioner outside the house and another part of the system is located indoors. Through a mechanical compression cycle and a system of refrigeration, the heat pump circulates refrigerant that moves between indoor and outdoor spaces, bringing warm and cool air to the opposite place.

A heat pump works because heat energy is always present in the air, even when it is cold outside. The appliance extracts outside heat during the winter and moves it inside. In the summer, the heat pump moves heat from within the house outside. This can be advantageous to your energy bill, since the pump is merely moving heat energy, rather than generating it.

Heat Pump Refrigerant Charge

Refrigerant is an essential component of a heat pump and transports heat energy inside the system. Over time, this refrigerant may leak or break down. Believe it or not, you need refrigerant for both the heating and cooling part of the heat pump. Refrigerant is able to effectively change from a liquid to a gaseous state and is thus perfect for moving heat energy the way a heat pump does.

The compressor in your heat pump places refrigerant under pressure so that it can move the indoor and outdoor heat energy. When there is a drop in the level of refrigerant, also known as the refrigerant's charge, you need the help of a professional. Since refrigerant is a dangerous chemical, only those who are certified and trained under Environmental Protection Agency standards should work with it. In addition, certain jurisdictions have laws that limit how refrigerant may be stored or disposed of. Entrusting this task to a professional is important.

What to Look For

If you notice that your heat pump isn't as effective as it once was, there may be a problem with your refrigerant levels. Low refrigerant can cause coils in the heat pump to freeze over and the compressor to overheat. This could lead to the destruction of the entire unit. In addition, if you see any buildup of liquid or leaks on any part of the system, the refrigerant might be leaking. Over time, hoses that break down or other structural problems can cause leaks. If you hear a hissing noise or see ice on the heat pump coils, contact a service professional right away.

A technician may add heat pump freon to your unit, accomplished by connecting gauges to the refrigerant hoses while the heat pump is running. He'll then take readings of the input and output hoses to verify that the freon, or refrigerant, is at the temperature it should be. If it is not, he may need to add refrigerant. You'll note that the technician will never turn the refrigerant container upside down while topping off the system, as this could cause liquid freon to flood the compressor and destroy the heat pump.