E055 on a CTC control system alarm/information platform: Incorrect/wrong phase sequence: compressor would rotate the wrong way; two phases must be swapped with the supply isolated. Generally occurs only at installation
Short answer
On a CTC heat pump, E055 means: Incorrect/wrong phase sequence: compressor would rotate the wrong way; two phases must be swapped with the supply isolated. Generally occurs only at installation. 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: Incorrect/wrong phase sequence: compressor would rotate the wrong way; two phases must be swapped with the supply isolated. Generally occurs only at installation.
Part involved: mains supply phase order.
Likely causes:
- Two supply phases connected in the wrong order.
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.
Manual reset: Press "Reset alarm" on the display; a persisting fault must be rectified before it can be reset.
What you can check
- Note the alarm code/text, the product model and serial number and contact your installer.
What the engineer will check
- Isolate the supply and swap two phases at the incoming supply to the product.
Who to ask for: electrical.
Certification: Qualified electrician.
What you might notice
Sources
- CTC EcoZenith i255 Installation and Maintenance Manual (400V 3N~/230V 1N~/230V 3~) ↗ · 162 505 67-9 CR01164 2026-05-10 · page 81 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026