CH15 on a LG heat pump: Water pipe overheated – leaving water temperature exceeded the protection limit
Short answer
On a LG heat pump, CH15 means: Water pipe overheated – leaving water temperature exceeded the protection limit. 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: Water pipe overheated – leaving water temperature exceeded the protection limit.
Part involved: leaving water / water pipe temperature sensor, backup heater.
When it shows: Leaving water above limit: 57 °C (R410A split), 65 °C (R32 split), 67 °C (Monobloc with optional heater, Gen1 TS manual), 72 °C (Hydrosplit, Gen1/Monobloc S R32, split with integrated heater), 75 °C (R290 installer manual) / 82 °C (R290 TS guide), 90 °C (High Temperature split).
Likely causes:
- Abnormal operation of electric (backup) heater; external heat source (boiler/solar) not hydraulically decoupled so hot water is introduced; bad water pipe sensor; indoor Main PCB defect.
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: no.
Manual reset: Service-engineer repair and restart required (LG: resumed only after certificated professional's check).
What you can check
- Read the code on the controller (LG shows 'CH' + number; older wired controllers alternate 'CH' and the number) and note it together with the model number. Report it to your installer or an LG-authorised service centre – LG owner's manuals say an error code generated by self-diagnosis is a reason to call the service. This is an 'Error'-class fault: LG says the system can only be resumed after a qualified professional has checked it, so do not keep trying to restart it.
What the engineer will check
- Measure actual pipe temperature with a thermometer; check backup-heater control and relay, external boiler/solar interface and decoupling, sensor position and resistance; replace sensor or Main PCB.
Who to ask for: Heating/heat pump engineer (wet-side hydraulics).
Certification: None statutory for sealed-system wet-side work; G3 unvented qualification if the DHW cylinder is worked on.
What you might notice
Sources
- AIR-TO-WATER HEAT PUMP SERVICE MANUAL (General) – R32 Hydrosplit, MFL68682007 ↗ · MFL68682007 · page 71, 91 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026