LE on a Mitsubishi Electric Ecodan: Boiler operation error (boiler running but zone flow stays cold)
Short answer
On a Mitsubishi Electric heat pump, LE means: Boiler operation error (boiler running but zone flow stays cold). 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: Boiler operation error (boiler running but zone flow stays cold).
Part involved: Boiler / THW6 / boiler signal wiring OUT10.
When it shows: Boiler running and THW6 < 30C for 60 consecutive minutes.
Likely causes:
- 1 THW6 detached from holder; 2 Incorrect wiring FTC (OUT10) to boiler; 3 Boiler fuel run out or boiler OFF; 4 Boiler failure; 5 FTC board failure.
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 as auto-resetting; code remains until reset.
Manual reset: Installation manuals: press F4 (RESET) then F3 (Yes) on the main remote controller (older controllers: hold button E for 3 s); 'To cancel error codes please switch system off'. Fix the cause first.
What you can check
- Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check the boiler has power/fuel and is not showing its own fault.
What the engineer will check
- 1 Reattach THW6; 2 Check wiring (PAC-TH011HT-E manual); 3-4 Check status of the boiler; 5 Replace board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
What you might notice
What owners and engineers report
9 owner and engineer reports mention this.
- No heating on the Ecodan: 9 reports
Sources
- Ecodan EHPT20X-MEHEW Service Manual (OCH814A) ↗ · OCH814A · page 62 (10-4 Self-diagnosis and action) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026