FAQ - Heat pumps

Potential problems with heat pumps during colder seasons

In cold weather, many heat pump owners complain about either low performance or smoke coming out of their heat pump. The vast majority of those cases do not indicate a faulty product; as a matter of fact, it is a heat pump characteristic which can be explained with simple physics:

  1. Heat pumps not heating / low performance:

The higher the temperature difference between pool water and outside air, the higher the heat loss through the water surface. Even a roofed pool has high temperature losses – the whole space under a pool roof is „heated“ by the pool water surface. That alone puts more pressure on the heat pump.

In addition to the above the heat pump effectiveness is the lower the lower are the outside air temperatures.


Heat pump Rapid Inverter (565RIC040)

  • By air temperature 26 °C and humidity 80% the heating performance of the heat pump is 15 kW and the COP up to 16.
  • The same heat pump has by air temperature +5 °C only approx. 7 kW of heating power, with a maximum COP of 6.
  • By air temperature -5 °C the heating output of the same heat pump does not go over 5,5 kW, with a maximum COP slightly above 4.

Thus, the heat pumps is working normally (it is heating as it should), but with the lower heating output by lower air temperatures it is not able to compensate for the water surface heat loss. At night, the water temperature may drop as much as by 2-3 °C; the heat pump may then increase the water temperature by 2-3 °C again during the day, but it may not be able to compensate all the heat losses AND increase the pool water temperature.

This temperature loss effect may lead the customer to think that the heat pump performance is either too low or even that the heat pump is defective.

  1. The heat pump is “smoking” or is “on fire” / it is “freezing up”:

Automatic defrost is a function available on mid- and high-class heat pumps. The function allows the heat pump to operate even under cold weather conditions.

As an effect of colder outside air together higher air humidity the frozen condensate may start building up on the heat exchanger/evaporator. To eliminate the danger of damage from an ice build-up, the heat pump has an automatic defrost function. In the defrost mode, the hot coolant goes directly into the evaporator in order to warm it up and thaw any ice deposited there.

During the defrosting phase there is steam coming up from the heat pump – it is not smoke. The heat pumps is not heating during defrosting, since it is using all the heat it generates to defrost the ice deposits.