I’ve always had a problem with the term ‘Heat pump’, because I think it can be confusing. A heat pump is indeed a refrigeration unit with a reversible cycle, able to operate both for heating and cooling, as I’m explaining in this new tutorial on our Tempco Youtube channel (turns English subtitles on). As we all know, chillers don’t really ‘produce cold’, but they remove heat from the inside sending it to a condenser. That’s exactly what happens in the home refrigerators we all have in our kitchens, if we check the back of it we can feel it hot.
The heat pump thus operates as a refrigerator during the summer, removing heat from the ambient to be conditioned using a cold heat exchanger, called evaporator. Here, the freon evaporates removing the heat from air, liquid or fluid to be cooled, producing as an effect the perception of ‘cold emission’. The freon then carries the heat removed from the ambient to the warm heat exchanger, called condenser, dissipating the energy on the outdoor and thus emitting heat.
During the winter season, a cycle inversion valve swaps the functions of the two exchangers, transforming the condenser/heater into a cooler/evaporator that removes the heat from the external ambient, carrying it to the former-evaporator transformed into a condenser, that brings the thermal energy inside the ambient to be heated.
With very low ambient temperatures in winter, and high relative humidity, the external exchanger can often become completely iced, so that a defrost cycle is triggered automatically. The operating cycle is reversed for a few minutes allowing the hot freon to flow inside the external exchanger in order to melt the ice and restore its efficiency. During the operation, ambient heating will stop for a while, but it usually takes only a few minutes.