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What Makes a Heat Pump Different from an Air Conditioner?

question-mark-badgeHere’s a confusing fact when it comes to the difference between air conditioners and heat pumps: an air conditioner is a type of heat pump. Technically, the job of an AC is to pump heat from one location to another. It removes heat from inside a building and releases it outside. But, in the world of residential and commercial HVAC, when somebody talks about a “heat pump,” what they mean is a refrigeration device, similar to an air conditioner, that can switch the direction it moves heat. So when you arrange to have a heat pump installed, or you need service for your heat pump in Cranford, NJ, the device you mean is a comfort system that offers both heating and cooling.

Okay… so what makes a heat pump different from an air conditioner? Yes, you know it can offer both heating and cooling, but what actual components allow a heat pump to do both those jobs even though it otherwise works like an air conditioner? (I.e. it has a compressor that circulates refrigerant between a set of indoor and outdoor coils.)

The Basic Heat Pump Difference

Although there are a number of small changes in how a heat pump operates compared to a standard central AC, the core difference is actually an easy one to describe—although it’s not “easy” when it comes to repairs and replacements. It’s a part called the reversing valve, and it controls the direction refrigerant travels when it leaves the compressor in the outdoor cabinet. Something as basic as which direction the refrigerant moves first alters the entire operation of the heat pump.

This is how it works: refrigerant leaving the compressor is in a hot, high-pressure gaseous state. In a standard air conditioner, the refrigerant lines exiting the compressor lead to the outdoor coils, where exposure to the air causes the refrigerant to condense, losing heat and lowering in temperature. In a heat pump, the refrigerant instead moves into the reversing valve, an assembly with a slider inside it that can shift to route the refrigerant either toward the outdoor coils—as in an air conditioner—or toward the indoor coils.

The valve is controlled by an electric signal: whether in an excited or unexcited state will determine the valve’s position. (This depends on the brand of heat pump; there’s no set standard.) If the valve is set so that the hot gaseous refrigerant leaves the compressor and is directed toward the indoor coil, the hot refrigerant will condense indoors and release heat. In other words, it’s in heating mode. If the valve is in the other position, the heat pump will act like a standard air conditioner.

There are a few other differences to note. In heating mode, a heat pump uses less refrigerant. The extra refrigerant must be stored until needed again, and it is held in a suction accumulator. This device also helps protect the compressor from slugging, which is when cold refrigerant travels the wrong direction and enters the compressor. This is a potential threat in a heat pump that can cause the compressor to burn out. As an additional precaution, heat pump compressors are outfitted with a crankcase heater to warm up any frozen refrigerant that may slip into the compressor.

Call on Air Creations, Inc. for any assistance you need with a heat pump in Central or Northern New Jersey. Since 1987, “We Do It Right!”

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