SolarpunkHomes
Sign inCall us · +44 7510 081687
Heat pumps
Heat pumps · Error codes · Trianco
F21Trianco

F21 on a Trianco heat pump: Overspeed Fault

Short answer

On a Trianco heat pump, F21 means: Overspeed Fault. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.

Reviewed 23 September 2026 · 2 sources

What it means

On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)

The manual says: Overspeed Fault.

Part involved: compressor driver / inverter board.

Likely causes:

  • The compressor is running abnormally.

On the Activair Pro (AI) R290 6/12/17kW

The manual says: Overspeed Fault.

Part involved: compressor driver / inverter board.

Likely causes:

  • Compressor operating speed is abnormal.

Is it safe?

Does the heat pump stop?Not stated
Engineer needed?Yes

The manual does not say whether the heat pump stops.

What you can check

  • Note the exact code shown on the controller (a photo helps) and report it to your installer or the manufacturer's service line.
  • Check the heat pump's supply breaker/isolator at the consumer unit is on (do not open any casing).

What the engineer will check

On the Activair R290 Indoor (3.2kW wall hung / 5kW floor standing)

  • Check whether the compressor cable is normal and whether the compressor is blocked.

Who to ask for: heat pump electrical / inverter.

Certification: Electrical competence; manufacturer-trained heat pump engineer.

On the Activair Pro (AI) R290 6/12/17kW

  • Check compressor wiring and verify that the compressor is not mechanically blocked.

Who to ask for: heat pump electrical / inverter.

Certification: Electrical competence; manufacturer-trained heat pump engineer.

What you might notice

Sources

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026