motor-p-error on a Thermia Diplomat: Deployed overload relay (overcurrent relay compressor), deployed overload relay for outdoor unit fan. On certain models alarms from the brine pump and soft starter can also occur. Compressor stopped
Short answer
On a Thermia heat pump, motor-p-error means: Deployed overload relay (overcurrent relay compressor), deployed overload relay for outdoor unit fan. On certain models alarms from the brine pump and soft starter can also occur. Compressor stopped. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Deployed overload relay (overcurrent relay compressor), deployed overload relay for outdoor unit fan. On certain models alarms from the brine pump and soft starter can also occur. Compressor stopped.
Part involved: motor protection, soft starter.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Manual reset: Set operating mode OFF then back to the desired mode.
What you can check
- Note the exact alarm text. Check the heat pump's breaker/isolator at the consumer unit is on and has not tripped. Acknowledge once by setting operating mode OFF then back; 'Other alarm message: reset the alarm; if the alarm remains, contact a service technician' (VUGFD302 p.16).
What the engineer will check
- Phases/fuses, soft starter, motor protection setting, compressor windings, brine pump WSK (VMGFC302 Table 15). Causes per the equivalent Danfoss service instructions VMGFC302 (same Danfoss-era controller) - not stated in the Thermia user manual.
Who to ask for: heat pump engineer.
Certification: Qualified electrician / heat pump engineer (electrical fault-finding).
What you might notice
Sources
- User manual Atria, Atria Duo, Atria Duo Optimum, Atria Optimum, Comfort, Diplomat, Diplomat Duo, Diplomat Duo Optimum (G2), Diplomat Optimum (G2) - 086U6297 Rev. 6 EN ↗ · 086U6297 Rev. 6 · page printed p.41 (PDF p.43) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026