Fault-in-I-O-card-control-cabinet-electric-boiler on a Worcester Bosch Greensource air to water heat pump: Alarm window: Fault in I/O card control cabinet/electric boiler
Short answer
On a Worcester Bosch heat pump, Fault-in-I-O-card-control-cabinet-electric-boiler means: Alarm window: Fault in I/O card control cabinet/electric boiler. 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: Alarm window: Fault in I/O card control cabinet/electric boiler.
Part involved: I/O board internal unit.
When it shows: Internal communication error in internal unit.
Likely causes:
- Internal communication error in internal unit.
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: no.
Manual reset: Select Acknowledge on the control panel (manual says there is never a risk in resetting an alarm); heat pump restarts within ~15 min if there is demand. Call the installer if the alarm recurs.
What you can check
- Read and note the full alarm text shown on the controller and pass it to your installer.
- Select Acknowledge on the control panel (manual says there is never a risk in resetting an alarm); heat pump restarts within ~15 min if there is demand. Call the installer if the alarm recurs.
What the engineer will check
- Check whether LED on I/O board is flashing.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
What you might notice
Sources
- Installation Manual Air to Water Heat Pump with DHW distribution unit Greensource 6/7/9.5 kW ↗ · 6 720 641 467 (2010/01) · page 43 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026