E027 on a CTC control system alarm/information platform: Comm. error HP: display card (A1) cannot communicate with the HP control card (A5)
Short answer
On a CTC heat pump, E027 means: Comm. error HP: display card (A1) cannot communicate with the HP control card (A5). The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Comm. error HP: display card (A1) cannot communicate with the HP control card (A5).
Part involved: display card A1 / HP control card A5.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
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.
- Check the heat pump isolator/consumer-unit breakers are on.
What the engineer will check
- Check communication cables and connectors between the named boards.
- Check power supply to the named board.
Who to ask for: heat pump controls / electrical.
Certification: Electrical competence for work inside control panels.
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