4-5 on a myenergi eddi solar immersion diverter: Back-Feed Voltage - unexpected voltage at heater output
Short answer
On a myenergi inverter, 4-5 means: Back-Feed Voltage - unexpected voltage at heater output. The inverter stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Back-Feed Voltage - unexpected voltage at heater output.
Likely causes:
- Heater terminals connected to a supply or faulty heater wiring.
Is it safe?
Switch the inverter off at its isolator and call an engineer.
| Does the inverter stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The inverter stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Reboot device from menu or via supply breaker.
What you can check
- Read the fault on the eddi screen. Check the eddi supply breaker is ON. Switch off and call an electrician.
What the engineer will check
- Check heater output wiring for back-feed/incorrect connections.
Who to ask for: Electrician / plumber-electrician for immersion circuits.
Certification: Competent electrician (BS 7671); immersion heater work to Part P.
What you might notice
Sources
- myenergi Help Centre - eddi Installers > Fault Codes ((4)1 to (4)8) ↗ · Help Centre article · page 30222348659473 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026