In this instance, it is perhaps easier to answer the second part of the question first. Heat pumps are popular because after the initial outlay, they are very economical to run. It’s that simple. They are economical to run as they do not generate heat but, instead, they transfer heat from outside your home into it in the winter, or the other way round in the summer.
As to how a heat pump actually works, well it’s not exactly rocket science, but it is fascinating and scientific all the same.
A heat pump is a clever thing. It is a bit like a chameleon, as it can adapt to its surrounding environment. Consequently, through just the flick of a switch, a heat pump can go from heating your home in the harshest of winters, to keeping it cool in the hottest of summers.
A heat pump is made up of two main units, the indoor one usually located in the attic or basement, and an outside one adjacent to your home. The indoor unit is primarily made up of evaporator coils and an air handler, while the outside unit will comprise a fan, condenser coils and a compressor. Located between the two units are two expansion valves.
The pipework that connects the indoor and outdoor units contains a refrigerant, some of which will be in a liquid or gaseous state, those sections will depend on whether the unit is acting as an air conditioner to cool your home, or as a heater to warm the air circulating throughout it. So, lets have a look at what happens when you use the heat exchanger in the winter to warm your home.
It may sound odd to say that the exchanger takes the heat from the outside air and brings it into your home, especially when the outside temperature is below freezing point. In reality, an average heat pump can work efficiently when the outside air temperature is as low as -10 degrees Celsius, while top-of-the range models can remain efficient in outside temperatures up to -25 degrees Celsius.
“But how is that possible?” we hear you ask. Now here comes the science bit, as that is all down to pressurizing the coolant that runs through your system.
Let’s look at what happens throughout the process that results in warm air being circulated through your home. To begin with, the refrigerant that is contained within the copper pipework of your heat pump absorbs heat, and it is the temperature of the refrigerant in the evaporator coils in your home that will dictate the temperature of the air inside your home as the blower that is connected to the evaporator coil is responsible for distributing the air throughout your home.
Just prior to being released into the evaporator coils, the refrigerant goes through a compressor which heats up the refrigerant (this is a scientific process, the refrigerant is not heated by the compressor). When the refrigerant is released, it is then a super-hot gas and the condenser coils heat up. Then, by the time that refrigerant condenses back to a liquid state and reaches the outside unit, it’s temperature will be well below freezing point, which is why it can then absorb heat, even from sub-zero temperatures outside. Note that the refrigerant remains a liquid, even at -25 degrees Celsius. If the refrigerant’s temperature is -25 degrees Celsius and the outside temperature is -15 degrees Celsius, the refrigerant can absorb 10 degrees of ‘heat’.
The clever bit with a heat pump is that it is simple to then reverse the system, so that warm air from your home is used to heat the air outside, and then, by the time the refrigerant makes its way back to the evaporation coil, it will be at a sub-zero temperature, and the blower will then blow cool air throughout your home.
Of course, like all home heating and air conditioning systems, regular maintenance is strongly recommended. So, if you haven’t got a maintenance contract in place and your heat pump hasn’t been inspected for a while, why not give us a call here at A&E and we’ll be more than happy to come out, have a look at your unit, and advise you on the costs of a regular maintenance contract that will ensure your heat pump operates efficiently and doesn’t break down in the middle of summer or winter!