H31 on a Panasonic heat pump: Abnormal swimming pool sensor
Short answer
On a Panasonic heat pump, H31 means: Abnormal swimming pool sensor. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Abnormal swimming pool sensor.
Part involved: Pool temperature sensor (optional pool connection).
When it shows: Service-manual table judgement: Continue for 5 sec. (L, K, J MDC, J MXC, J AIO, H).
Likely causes:
- 1 Faulty connector connection. 2 Faulty swimming pool sensor. 3 Faulty indoor sub PCB.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Not stated in the Panasonic documents opened; protection counters lock out after the stated number of occurrences.
Manual reset: User: 'Error Reset' in the remote-controller Quick Menu (H/J/K/L controllers) or OFF/ON; engineer must clear the underlying cause (service manuals: 'When error happens, the power has to be reset').
What you can check
- Read and note the code shown blinking on the remote controller (also stored under System Check > Error history). Per the Panasonic operating instructions the user may switch the system OFF/ON at the remote controller and use 'Error Reset' in the Quick Menu; if the code returns, leave the system and contact the installer (UK user guide lists Panasonic technical support as the fallback).
What the engineer will check
- Check pool sensor connector and resistance on the optional/sub PCB; check pool setting; replace sensor or sub PCB.
Who to ask for: Heat pump engineer (Panasonic-trained).
Certification: None statutory; safe electrical isolation competence required.
Sources
- Service Manual Hydromodule WH-SDC0509L3E5/L6E5 with WH-WDG05LE5/07LE5/09LE5 (Order No PAPAMY2307068CE) ↗ · PAPAMY2307068CE · page 189 (error codes table); 199 (self-diagnosis) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026