Heat pumps · Error codes · Joule
71Joule · Modul-AIR exhaust air heat pump
71 on a Joule Modul-AIR exhaust air heat pump: Back up heater protection active
Short answer
On a Joule heat pump, 71 means: Back up heater protection active. 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: Back up heater protection active.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| 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 heating system pressure gauge reading against the value in your handover documents (manufacturer commissioning values: typically 1-2 bar) and that the filling loop is closed.
- Check the outdoor unit/air grilles are not blocked by debris, leaves or snow.
What the engineer will check
- Manual 'possible solution': Check sensor. Replace if necessary.
- Check water flow rate and temperature sensors.
- Check set-points and system design temperatures.
- Check refrigerant charge.
Who to ask for: heat pump engineer.
Certification: None specific.
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 106 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026