Heat pumps · Error codes · Joule
37Joule · Modul-AIR exhaust air heat pump
37 on a Joule Modul-AIR exhaust air heat pump: Lost connection with Green Comfort Module
Short answer
On a Joule heat pump, 37 means: Lost connection with Green Comfort Module. 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: Lost connection with Green Comfort Module.
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.
Manual reset: Installer override required.
What you can check
- Read and note the code shown on the controller display, then contact your installer or service engineer.
- Check the heat pump's breaker/isolator at the consumer unit is switched on (do not repeatedly reset if it trips).
What the engineer will check
- Manual 'possible solution': Check cable. Replace if necessary.
- Check communication cable between controller/PCB/driver board (type, polarity, termination).
- Check power supply to the remote module.
- Replace faulty PCB/controller if wiring is sound.
Who to ask for: heat pump controls / electrical.
Certification: Electrical competence.
What you might notice
Sources
- Joule Modul-AIR All-E, Modul-AIR All-E with Green Comfort Module & Modul-AIR Aqua - Installation & Maintenance Manual ENG-0026-07 (UK/IE) ↗ · ENG-0026-07 · page 105 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026