CH11 on a LG heat pump: Indoor unit & inverter PCB communication error (High Temperature split)
Short answer
On a LG heat pump, CH11 means: Indoor unit & inverter PCB communication error (High Temperature split). 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 THERMA V High Temperature Split
The manual says: Indoor unit & inverter PCB communication error (High Temperature split).
Part involved: indoor Main PCB ↔ indoor inverter PCB.
When it shows: Communication loss.
Likely causes:
- No signal communication between indoor unit and (indoor R134a) inverter PCB.
On the THERMA V R290 Monobloc
The manual says: Correspondence (communication) error between outdoor Main PCB and inverter PCB (R290 Monobloc).
Part involved: outdoor PCBs / harness.
When it shows: Loss of Outdoor-PCB ↔ Inverter-PCB communication.
Likely causes:
- Communication line between outdoor PCB and inverter PCB broken; inverter PCB damaged.
Is it safe?
On the THERMA V High Temperature Split
| 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).
On the THERMA V R290 Monobloc
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes – trouble clears when the condition is repaired; emergency operation must be restarted by the user after a power reset.
Manual reset: Not normally required; user restarts after power reset if emergency operation was running.
What you can check
On the THERMA V High Temperature Split
- 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.
On the THERMA V R290 Monobloc
- 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. For this 'trouble' class LG allows temporary emergency operation: if the controller shows a pop-up offering it you may accept (OK) as a stop-gap; running costs will be higher, so do not use it long term. Emergency operation does not restart by itself after a power cut – you must switch it back on at the controller. Check the heat pump's breaker/isolator at the consumer unit is on; if a breaker or RCD has tripped, do not keep resetting it – leave it off and call an engineer.
What the engineer will check
On the THERMA V High Temperature Split
- Check the communication cable terminations and polarity between the named PCBs, look for intermediate twisted joints, shorts or open circuits, check for noise sources near the cable, confirm supply voltage and earthing, check software/EEPROM versions of both PCBs are compatible, then replace the defective PCB.
Who to ask for: Heat pump engineer / electrician (inverter and PCB diagnostics).
Certification: Competent person for electrical work (BS 7671); isolate and wait 3 min for DC-link discharge.
On the THERMA V R290 Monobloc
- Check the communication cable terminations and polarity between the named PCBs, look for intermediate twisted joints, shorts or open circuits, check for noise sources near the cable, confirm supply voltage and earthing, check software/EEPROM versions of both PCBs are compatible, then replace the defective PCB. Check loose connectors/wiring between internal PCBs in the outdoor unit.
Who to ask for: Heat pump engineer / electrician (inverter and PCB diagnostics).
Certification: Competent person for electrical work (BS 7671); isolate and wait 3 min for DC-link discharge.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- No heating on the THERMA V R290 Monobloc: 1 report
Sources
- LG THERMA V High Temperature Installation Manual (AHUW166T3 / AHNW166T3 cascade R410A/R134a), MFL67212828 Rev.00 (2019) – ManualsLib 1770589 ↗ · MFL67212828 Rev.00_051519 · page 119 · Reviewed 23 September 2026
- LG THERMA V R290 Monobloc Installation Manual (HM..HF UB60 / UB40, PHCS0), MFL68681848 Rev.03 (2024) – ManualsLib 3668662 ↗ · MFL68681848 Rev.03_112224 · page 179 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026