CH37 on a LG THERMA V Monobloc: Pressure ratio too high – R410A Monobloc
Short answer
On a LG heat pump, CH37 means: Pressure ratio too high – R410A Monobloc. 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: Pressure ratio too high – R410A Monobloc.
Part involved: refrigerant circuit.
When it shows: Pressure ratio above limit.
Likely causes:
- Refrigerant-cycle abnormality (high discharge/low suction ratio).
Is it safe?
| 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
- 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.
What the engineer will check
- Check refrigerant charge, EEV, fan, water flow; LGMV pressures.
Who to ask for: Heat pump engineer with LG Therma V training; F-gas certified refrigeration engineer for refrigerant-circuit work.
Certification: F-gas certification (UK F-gas Regulation, Category I) for any refrigerant handling on R32/R410A units; for R290 units additionally competence in flammable (hydrocarbon) refrigerants (e.g. BESA/ACRIB HC safe handling).
What you might notice
What owners and engineers report
2 owner and engineer reports mention this.
- Keeps stopping / cutting out on the THERMA V Monobloc (R410A): 1 report
- No heating on the THERMA V Monobloc (R410A): 1 report
Sources
- LG Therma V AHBW A0 Series Service Manual (R410A Monobloc AHBW036H0, AHBW056A0…AHBW168A0), P/No. MFL58346405 (April 2013) – ManualsLib 3030181 ↗ · P/No. MFL58346405 · page 48 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026