How a Heat Pump Works.

How Heat Pumps work.
 
I will be providing you a detailed explanation as to how a heat pump works. If you have some difficulty following along with the  explanation which will get pretty technical, please refer to a previous article that I have written titled How an Air conditioner works.

To begin in the simple mode, a heat pump is very much like an air conditoner. As a matter of fact, an air conditioner looks and works just like a heat pump when the heat pump is in the cooling mode… In other words, it is doing exactly what an air conditoner will do when cooling.

However the heat mode is another story, as it must reverse its role and becomes a heating device.. The air conditioner can never reverse itself and become a heating device. Believe it or not, even when its freezing weather outside, the heat pump absorbs heat from the zero degree air outside and converts that energy to heat for us to use on the inside of the house. I know it sounds impossible to extract heat from zero degree air, but it is not black magic, as we have been doing this for many years.

Basically we pass refrigerant through the outdoor coil, and as the outside air passes over the outside coil, the freon absorbs the heat from the air even at relatively low outside temperatures. After the refrigerant passes through the outdoor coil we run it thru a compressor which will increase the temperature of the refrigerant to the point that it actually gives off heat when passed through the coil that is located inside the house.

Now don't get me wrong, its not easy to get heat from zero degree air, so as it might be expected, the heat pump works better  in warmer air than in cold air, but it is still able to extract heat from relativly cold air.  Now since its efficiency does decrease rapidly in regard to gathering heat from the cold air, on the very coldest days, we sometimes are required to kick in a back up heat. This backup heat is generally electrical in nature similar to the base board heat many of us are familiar with. The blower pushes air across the electrical heating coils any time the heat pump is having difficulty keeping up and provides heat when the heat pump is no longer able to extract sufficient heat from the cold air.

So you might ask, if the heat pump needs an electrical backup source, why don't we just use the electrical source to begin with and do away with the very expensive heatpump? The reason is very simple, as the heat pump can produce as much as 3 to 4 times more heat for the money as electrical base board heat or other souces of electrical heat, and heat pumps are rapidly becoming more and more efficient every year.

We can find heat pumps of all sorts today… such as window units, package units, split systems and PTACs. A good way to tell if your outside unit is a heat pump or air conditioner, is to look inside the outside unit. If it has a switching valve, then it is a heat pump. The switching valve is used to allow the refirgerant to flow in one direction for heating and in the opposite direction for cooling..

Ok so you say what is a switching unit… for the laymen, here is another easy way to determine if the unit is a heat pump or air conditiioner… Look at the thermostat… if the thermostat has a backup or secondary heat, then you can be relatively sure that your unit is a heat pump. However if its an air conditioner unit then it must have another source to heat the home . It is usually a gas furnace or other method.

A different sort of heat pump is called a Geothermal Heat Pump.  This type unit does not have the outdoor unit with the fan. Normally this system has a method whereby water pumped from an under ground well passes over the coil. This allows the refrigerant to extract heat from the water drawn from the well.  Without a doubt, the geothermal units are the most efficient systems currently on the market.  They work especially well since the temperature of the water from the well is at a constant temperature, compared to the extreme changes of the outside air which a normal heat pump must deal with.

The geothermal heat pumps are expensive compared to a regular heat pump, but they are more efficient and less troublesome.  Of course there is an added expense of digging and maintaining one or two wells, as normally the water is pumped from one well and returned to the other. If you cannot find an outside unit, then most likely you have a geothermal system.

Smiley Heating and Cooling is expanding in the Elizabeth City area of North Carolina.

Author
Tom Chambers