How does the defrost cycle work on Grant Aerona³ heat pumps?

As a heat pump extracts heat from the outside air, condensation can form on the finned evaporator coil and under low temperature conditions in winter months this will freeze. This is normal and a Grant heat pump is designed to cope with this by using the in-built ‘Defrost’ function.

The heat pump control system will detect that the evaporator coil has iced up and will automatically put the heat pump into the Defrost cycle. The fan will stop, and the flow of refrigerant in the heat pump is briefly reversed, taking a small amount of heat from the heating system to melt the ice on the evaporator. Once the evaporator is clear of any ice, the refrigerant flow is switched back to normal and the fan restarts. This is usually accompanied by a cloud of steam being blown out of the front grill of the heat pump. This is perfectly normal and is just the cloud of condensation formed from the melted ice on the evaporator.

Whilst the heat pump is not supplying heat to the heating system during the defrost period, this only lasts for a few minutes and should not be noticed. Any condensation formed during normal operation along with any water produced from normal operation will drip down into the base tray of the heat pump, where it can drain out and away from the unit. To avoid any water freezing in the base tray during winter months, there is an electric heating element that will automatically operate only when the air temperatures fall to 2.5°C.