E117 on a CTC control system alarm/information platform: Driver: Offline - communication error, heat pump (junction box) and driver not communicating
Short answer
On a CTC heat pump, E117 means: Driver: Offline - communication error, heat pump (junction box) and driver not communicating. 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: Driver: Offline - communication error, heat pump (junction box) and driver not communicating.
Part involved: inverter driver.
Likely causes:
- Heat pump and inverter driver not communicating.
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
- If the manual instruction applies, press "Reset alarm" on the display once and note whether the alarm returns (manual: press reset and check whether the alarm recurs).
- Note the alarm code/text, the product model and serial number and contact your installer and the driver error number shown.
What the engineer will check
- Check inverter driver, its supply voltage and temperature, and communication wiring.
Who to ask for: heat pump inverter / electrical.
Certification: Electrical competence; F-gas if refrigerant work needed.
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