E931 on a Rinnai heat pump: Comunication error with main controller
Short answer
On a Rinnai heat pump, E931 means: Comunication error with main controller. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 24 September 2026 · 2 sources
What it means
On the HPI (HPi32) R32 monobloc
The manual says: Comunication error with main controller.
Part involved: see manual.
On the R290 monobloc (HPR290)
The manual says: Internal communication error.
Part involved: controller / PCB communication.
Is it safe?
On the HPI (HPi32) R32 monobloc
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
On the R290 monobloc (HPR290)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
What you can check
- Note the code shown on the controller and the model number on the unit's rating label before contacting your installer.
- Check that the heat pump's isolator and consumer-unit breaker are on; do not open any casing.
What the engineer will check
On the HPI (HPi32) R32 monobloc
- Follow the manufacturer's troubleshooting for this code.
Who to ask for: Heat pump engineer.
Certification: Heat pump installer competence; F-gas and flammable-refrigerant (R32/R290) handling competence for any refrigerant-circuit work.
On the R290 monobloc (HPR290)
- Check communication cables and connectors between boards/controller.
- Check board power supplies.
- Check addressing and firmware compatibility.
- Replace the faulty board.
Who to ask for: Heat pump engineer.
Certification: Heat pump installer competence; F-gas and flammable-refrigerant (R32/R290) handling competence for any refrigerant-circuit work.
What you might notice
Sources
- Maxa i-32V5 Heat pump air/water inverters with axial fans - Controller Manual ↗ · page p.36 (MAXA i-32V5 controller manual) · Reviewed 24 September 2026
- Maxa i-290 Inverter air/water heat pumps with axial fans - Controller Manual (0106-0118) ↗ · page p.44 (MAXA i-290 controller manual) · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026