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

As a heat pump extracts heat from the outside air, condensation can form on the finned evaporator (outside coil) and under low temperature conditions in winter months this will freeze. The build up of ice will reduce a heat pump unit's ability to absorb heat from the air, which will affect the performance and efficiency of the heat pump. It is therefore important that any build up of ice is prevented. A Grant air source heat pump is designed to cope with this by using the in-built ‘defrost’ function.

With both the Aerona³ and Aerona 290 ranges, the defrost function works as follows:

1. The heat pump will detect when ice starts to form on the evaporator coil and will automatically operate its defrost cycle

2. The defrost function will stop the fan and briefly reverse the flow of the refrigerant in the heat pump, directing the hot refrigerant back into the ice-covered evaporator causing the ice to melt

3. 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. The defrost function is specifically designed to prevent the build up of ice, restoring the heat pump's performance and overall efficiency. 

How is condensation removed from the heat pump?

Any condensation formed during normal operation along with any water produced from the defrost cycle 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.

Further information about heat pumps

If you already have a Grant air source heat pump, please visit our online Customer Support Centre for homeowners where you can access a range of resources to help you understand and operate your heat pump heating system. 

If you are researching renewable heating solutions for your home, please visit our Knowledge Hub to read our guides, articles and case studies.