How the Grant Aerona defrost cycle works — step-by-step

How the defrost cycle works on Grant Aerona heat pumps

The defrost cycle on Grant Aerona heat pumps is designed to prevent the outdoor coil from freezing over. The coils are located outside, so they are exposed to the elements and can easily turn into a block of ice. When this happens, it prevents the heat pump from working properly and can cause damage to the unit. The Grant control system detects frost formation and runs a short, automated defrost cycle to melt the ice and restore normal operation.

Why the defrost cycle matters

When ice accumulates on the outdoor coil it prevents the unit from extracting heat from the air effectively. That loss of performance increases energy use, reduces indoor comfort and, if left uncorrected, can cause damage to the unit. The defrost cycle keeps the heat pump efficient and reliable through frosty British winters.

Step-by-step: what happens during a Grant Aerona defrost cycle

Grant Aerona air source heat pumps use a sophisticated control system to run a defrost cycle only when needed. The basic sequence is:

• Fan deactivation: The outdoor fan stops. Stopping the fan reduces the flow of cold air across the coil, which helps prevent further ice build-up while defrosting begins.
• Reversing the refrigerant flow: The system activates the reversing valve and briefly switches into cooling mode. Warm refrigerant is sent through the outdoor coil, melting frost in a similar way to running your freezer in reverse.
• Heat utilisation: The heat pump draws heat from the property’s heating system to assist the ice-melting process. Whilst this temporarily reduces the heat output to your home, it is a necessary and efficient way to maintain system performance. Some models may use a backup heating element to supplement heating during this phase.
• Cycle completion: Once sensors report the coil is clear of ice, the fan restarts and the compressor reverts to normal heating mode. The entire process typically takes between 3–10 minutes, depending on the severity of ice accumulation and ambient temperature.

Impact on home heating during defrost

While the defrost cycle is active, the heat pump temporarily ceases to supply heat to the building. This interruption typically lasts only a few minutes and doesn’t significantly affect indoor temperatures due to the thermal mass of the building and heating system.

Common questions about the defrost cycle

Why does the defrost cycle occur?

The defrost cycle occurs when condensation on the evaporator coil freezes in low temperatures. The heat pump control system detects this ice formation and initiates the defrost cycle to melt the ice, ensuring efficient operation of the heat pump.

How often does the defrost cycle happen?

The frequency of the defrost cycle depends on external temperatures. It is more common in winter months when temperatures are below 0°C. The exact frequency can vary based on local climate conditions and the specific heat pump model.

Does the defrost cycle affect my heating?

The defrost cycle temporarily stops the heat supply to your heating system. However, this typically lasts only a few minutes and does not significantly affect the building temperature. The brief interruption is necessary to maintain long-term efficiency of the heat pump.

Can I manually initiate the defrost cycle?

No, you cannot manually initiate the defrost cycle. The process is automatically controlled by the heat pump’s control system, which initiates the cycle when necessary based on its sensors and programmed algorithms.

How do I know if my heat pump is damaged?

If your heat pump isn’t providing enough heat, cycles unusually often, or is making strange noises, there may be a fault. If you see any of these signs, contact our professional heating engineers. If you reside in Southampton, Sussex, Portsmouth, or Hampshire, get the services of our trained heating engineers at Clean Heat Solutions — contact us or call 07391473964 and we’ll be happy to help.

Keeping your Grant Aerona operating efficiently in winter

To ensure efficient operation during winter:

• Keep all external doors and windows closed to maintain indoor temperature.
• Consider adjusting thermostat timings to prevent prolonged periods without heat production.
• Ensure regular maintenance is carried out, including checks for debris on the air inlet grill and evaporator.
• Have the system serviced annually by a competent heating engineer — see our heat pump servicing and maintenance service for more details.

Clean Heat Solutions installs and maintains air source systems — find out more on our air source heat pumps page or contact us directly.

Contact
Call Clean Heat Solutions: 07391473964
Email: info@cleanheatingsolutionskent.co.uk