In the world of HVAC, much ado has been made about whether people should use a heat pump unit in their home or not. Since we're talking about people's houses, we'll talk about the air cooled heat pump. The air cooled unit works with the split system in most homes, and we don't want to have to worry about drilling holes in the ground, or using boilers and chillers in such a small unit.
You may have heard that a heat pump is supposed to use 1/3 less electricity than conventional resistance heat units in a home. But what makes it worth using a heat pump? Is there a preferred geographical area that is better to use a heat pump? When making the decision, a person should consider as many of the variables as possible.
A heat pump is a variation of a typical air conditioning system. If you understand the heat displacement premise behind making an air conditioner work, you already have the basic understanding of how a heat pump works. An air conditioning unit pulls the heat out of the air in the house using a refrigerant which has been cycled through a condensing unit outside the home. The refrigerant is heated up as it runs through the evaporator coil inside the home... the refrigerant actually evaporates as it draws more heat into it, hence the name; evaporator coil.
From there, the refrigerant is pulled through a copper line into the condensing unit outside of the house. The condensing unit then pulls the heat out of the refrigerant and releases it into the air. That is why you can feel warm air coming from the outside unit in the summer time. From there, the refrigerant is compressed and cooled, then cycled through the evaporator coil once again. This process causes cool air to be discharged from your vents inside the house, and warm air to be discharged outside of the home.
Now, what if we were to reverse the cycle just described? What if we could cause a unit to blow cool air on the outside and warm air on the inside? Well the answer is simple. We would have a heat pump. That is in effect, what a heat pump does - it pulls the heat from the outside air, and releases it inside the home. This allows a heat pump to run by using no more electricity than your air conditioner does during the summer, while typical resistance heat costs significantly more to run since it uses a toaster-like burner to heat the air in a home. The heating element draws significantly more amperage than a unit running in heat pump mode.
The problem is that the outside temperature can get too low for the unit to effectively pull heat out of the outside air. That's why your normal, everyday garden variety heat pump has fail safe mechanisms built into it. For instance, there are defrosting mechanisms to keep the refrigerant from getting too cold and seizing up the compressor and causing significant damage which will cost hundreds of dollars to repair. There is also a backup resistance heat coil that kicks in when a sensor on the outside unit determines that the outside temperature is too low for the refrigerant to effectively draw any heat from the air.
With this being said, a person must think about the climate in the winter in their locale before deciding to use a heat pump. Another thing to think about is that summer and winter aren't the only seasons in the year. There are cold snaps both early in the fall and late in the spring. Although one may not use the heat pump for a big portion of the winter, he or she may use it quite a bit in the fall and spring. These things need to be determined before installing one of these units in climates with cold winters. A heat pump unit costs more than a resistance heat unit, so you need to ask yourself, "Am I going to make up the difference in price through energy savings over the course of the life of the unit?" That is a question for your local air conditioning contractor to answer as much as for yourself to research.
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