E20 on a Technibel S.A.S. Technibel PHRIE / PHIE inverter monobloc air-to-water: Automatic address setting failure - A3 cannot receive any serial signal from A2 (A2 not detected)
Short answer
On a Technibel S.A.S. heat pump, E20 means: Automatic address setting failure - A3 cannot receive any serial signal from A2 (A2 not detected). 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: Automatic address setting failure - A3 cannot receive any serial signal from A2 (A2 not detected).
Likely causes:
- A2 not detected during auto-address.
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.
Resetting itself: Manual reset: fault memorised by A2 board; reset by A2 RESET button (5 s), setting system control to OFF, or switching off power (power-off recommended for E15/E16/E20/L02/L08/L09/L10/L13/F29/F31).
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