Heat pumps · Error codes · Warmflow
P01Warmflow
P01 on a Warmflow heat pump: Heating Return Temperature Sensor Error
Short answer
On a Warmflow heat pump, P01 means: Heating Return Temperature Sensor Error. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 3 sources
What it means
The manual says: Heating Return Temperature Sensor Error.
Part involved: temperature sensor/thermistor.
Likely causes:
- The temperature sensor is faulty or disconnected.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
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
- Test the operation of the heating return temperature sensor and re-connect/replace if necessary.
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
- Warmflow High Efficiency Variable Speed Air Source Heat Pumps A-Series AS01-R290 / AS02-R290 / AS03-R290 - User, Installation & Service Instructions, Guarantee (9009049 Rev D) ↗ · 9009049 Rev D · page 56 · Reviewed 23 September 2026
- Warmflow High Efficiency Variable Speed Air Source Heat Pumps A-Series AS01-R32 / AS02-R32 / AS03-R32 - User, Installation & Service Instructions (9007723 Issue C) ↗ · 9007723 Issue C · page 55 · Reviewed 23 September 2026
- Warmflow High Efficiency Variable Speed Air Source Heat Pumps A-Series AS01 / AS02 / AS03 (R410A Zeno) - User, Installation & Service Instructions (Issue 7) ↗ · Issue 7 · page 48 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026