H01-5803 on a Worcester Bosch Bosch Compress Hybrid 3400i AW: No power supply at compressor (Alarm)
Short answer
On a Worcester Bosch heat pump, H01-5803 means: No power supply at compressor (Alarm). 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: No power supply at compressor (Alarm).
Part involved: outdoor unit controller / compressor drive.
When it shows: No power supply to the compressor (outdoor unit locked).
Likely causes:
- No power supply to the compressor (outdoor unit locked).
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: Reset via HPC 410 fault menu after cause removed (engineer).
What you can check
- Read and note the full code (and sub-code) shown on the controller and pass it to your installer.
- Check the heat pump isolator and consumer-unit breaker(s) are switched on; if a breaker has tripped more than once, leave it off and call an engineer.
What the engineer will check
- Check compressor wire and high pressure switch connections.
Who to ask for: F-gas refrigeration engineer / heat pump installer.
Certification: F-gas certification (Category I) required for refrigerant circuit work; qualified electrician for electrical work.
What you might notice
Sources
- Installation Instructions Compress Hybrid 3400i AW HC3400iAW 8 l ↗ · 6721861825 (2023/08) · page 43 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026