H65 on a Panasonic heat pump: Deice circulation error
Short answer
On a Panasonic heat pump, H65 means: Deice circulation error. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the Panasonic, all models
The manual says: Deice circulation error.
Part involved: Water flow switch; water pump; buffer tank (if used).
When it shows: During startup and operation of deice (mode 2), the water flow (> 10l/min) detected by the water flow switch is used to determine deice circulation error. Service-manual table judgement: Continue for 10 sec. (F).
Likely causes:
- 1 Water flow in air-to-water heatpump indoor unit circuitry. 2 Faulty indoor unit water flow switch. 3 Faulty indoor unit water pump. 4 Faulty indoor unit PCB.
On the Aquarea J Generation
The manual says: Abnormal deice water circulation.
Part involved: Water flow switch; water pump; buffer tank (if used).
When it shows: Water flow > 7 l/min continuously for 20 seconds during anti-freeze deice (J mini monobloc and J T-CAP monobloc tables). Self-diagnosis pages still describe deice (mode 2) flow > 10 l/min (mini) / > 5 l/min (T-CAP) for 10 s.
Likely causes:
- Water pump (table). Self-diagnosis: 1 Water flow in air-to-water heatpump indoor unit circuitry. 2 Faulty water flow switch. 3 Faulty water pump. 4 Faulty indoor unit PCB.
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.
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 water flow during defrost (mode 2); check water flow switch and water pump; check buffer tank arrangement if fitted; check indoor PCB.
Who to ask for: Heat pump / heating engineer (hydraulics).
Certification: None statutory for water-side work; G3 unvented-cylinder competence if cylinder safety devices are involved.
What you might notice
What owners and engineers report
3 owner and engineer reports mention this.
- No heating on the Aquarea J Generation: 2 reports
- Outdoor unit frozen / iced up on the Aquarea J Generation: 1 report
Sources
- Service Manual Mono bloc Unit WH-MDC05F3E5 (Order No PAPAMY1311029CE) ↗ · PAPAMY1311029CE · page 87 (error codes table) · Reviewed 23 September 2026
- Service Manual Mono Bloc Unit WH-MDC05J3E5 / WH-MDC07J3E5 / WH-MDC09J3E5 (Order No PAPAMY2003034CE) ↗ · PAPAMY2003034CE · page 164 (error codes table); 180 (self-diagnosis) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026