F34 on a Panasonic heat pump: Indoor water heat exchanger leak
Short answer
On a Panasonic heat pump, F34 means: Indoor water heat exchanger leak. 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: Indoor water heat exchanger leak.
Part involved: Indoor water heat exchanger.
When it shows: Not stated in the documents opened.
Likely causes:
- Not stated in the Panasonic documents opened (operating instructions list code and title only).
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| 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
- Treat as a possible refrigerant-to-water heat exchanger breach: isolate the unit, ventilate if refrigerant is suspected (R32/R290 are flammable), leak-test the plate heat exchanger and follow the service manual.
Who to ask for: F-gas certified refrigeration / heat pump engineer (Panasonic-trained).
Certification: UK F-gas certification (Category I) for any refrigerant-circuit work; flammable-refrigerant competence for R32 (J/K) and R290 (L/M) units.
What you might notice
Sources
- Operating Instructions Air-to-Water Heatpump WH-SDC0309K3E5/K6E5 + WH-UDZ03-09KE5, WH-SXC09K3E5/12K6E5 + WH-UXZ09/12KE5 and 3-phase variants (WEB-ACXF55-36190-EN) ↗ · WEB-ACXF55-36190-EN FS0223-0 · page 51 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026