E05 on a Technibel S.A.S. Technibel PHRIE / PHIE inverter monobloc air-to-water: A2 to A3 serial signal sending failure
Short answer
On a Technibel S.A.S. heat pump, E05 means: A2 to A3 serial signal sending failure. 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: A2 to A3 serial signal sending failure.
Likely causes:
- A2-A3 connection.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Automatic stop; if the fault lasts <30 min it clears automatically, if >30 min it is memorised (AL LED steady) and needs manual reset (A2 RESET button 5 s, system control OFF, or power off).
What you can check
- Note the code/LED pattern and the model from the rating plate, then contact a heat pump/refrigeration engineer.
- Check the heat pump's breaker/isolator at the consumer unit is on.
What the engineer will check
- Check OC connector.
- Check A2 and A3 boards.
Who to ask for: refrigeration / heat pump engineer.
Certification: Electrical competence for work inside the unit.
What you might notice
Sources
- Technibel PHRIE / PHIE inverter monoblock air to water heat pump, medium temperature, R410A - Service Manual (Jun. 2015, 10 12 211 - GB - 06) ↗ · 10 12 211 - GB - 06 · page 95 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026