Heat pumps · Error codes · Trianco
P09Trianco · Activair R410A indoor wall hung 3kW (S300)
P09 on a Trianco Activair R410A indoor wall hung 3kW: Anti-freeze temp. failure (the anti-freeze temp. sensor is open or short circuit)
Short answer
On a Trianco heat pump, P09 means: Anti-freeze temp. failure (the anti-freeze temp. sensor is open or short circuit). The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Anti-freeze temp. failure (the anti-freeze temp. sensor is open or short circuit).
Part involved: temperature sensor/thermistor.
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
- Check or change the anti-freeze temp. sensor.
Who to ask for: heat pump controls / electrical.
Certification: Competent heat pump engineer; electrical competence for work inside the unit.
What you might notice
Sources
- Trianco Activair Wall Hung Air Source Heat Pump S300 (R410A indoor) - Installation Operation and Service Manual ↗ · 2023-07 · page 32 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026