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Heat pumps · Error codes · Trianco
P02Trianco

P02 on a Trianco heat pump: Water Out Sensor Fault

Short answer

On a Trianco heat pump, P02 means: Water Out Sensor Fault. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.

Reviewed 23 September 2026 · 5 sources

What it means

On the Activair Commercial R290 50kW (FG9550)

The manual says: Water Out Sensor Fault.

Part involved: temperature sensor/thermistor.

Likely causes:

  • The temperature sensor is open or short circuited.

On the Activair High Temperature R290 (5/9/15/22kW)

The manual says: Water Outlet Temp. Sensor Fault.

Part involved: temperature sensor/thermistor.

Likely causes:

  • Sensor open/short circuit or disconnected.

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

The manual says: Outlet Water Temp. Sensor Fault.

Part involved: temperature sensor/thermistor.

Likely causes:

  • The temp. sensor is broken or short circuit.

On the Activair R410A indoor wall hung 3kW (S300)

The manual says: Top tank water temp. sensor failure (sensor is open or short circuit).

Part involved: temperature sensor/thermistor.

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

The manual says: Outlet Water Temp. Sensor Fault.

Part involved: temperature sensor/thermistor.

Likely causes:

  • The temp. sensor is broken or short circuit.

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 Commercial R290 50kW (FG9550)

  • Check and replace outlet water temperature sensor.

Who to ask for: heat pump controls / electrical.

Certification: Competent heat pump engineer; electrical competence for work inside the unit.

On the Activair High Temperature R290 (5/9/15/22kW)

  • Check the connection.
  • Measure the resistance of sensor.
  • if lower than 100 ohm or higher than 500 kohm, replace it.

Who to ask for: heat pump controls / electrical.

Certification: Competent heat pump engineer; electrical competence for work inside the unit.

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

  • Check or change the temp. sensor.

Who to ask for: heat pump controls / electrical.

Certification: Competent heat pump engineer; electrical competence for work inside the unit.

On the Activair R410A indoor wall hung 3kW (S300)

  • Check or change the water top tank temp. sensor.

Who to ask for: heat pump controls / electrical.

Certification: Competent heat pump engineer; electrical competence for work inside the unit.

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

  • Check or change the 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

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

Reviewed: 23 September 2026