Heat pumps · Error codes · Worcester Bosch
A01-5808Worcester Bosch · Bosch Compress Hybrid 3400i AW
A01-5808 on a Worcester Bosch Bosch Compress Hybrid 3400i AW: AC input zero cross error (Info)
Short answer
On a Worcester Bosch heat pump, A01-5808 means: AC input zero cross error (Info). The heat pump keeps running. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: AC input zero cross error (Info).
Part involved: outdoor unit controller / compressor drive.
When it shows: AC frequency < 40 Hz or > 70 Hz, or no AC zero cross signal.
Likely causes:
- AC frequency < 40 Hz or > 70 Hz, or no AC zero cross signal.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Information only |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: yes.
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 input voltage between all phases and PEN; if within limits and persists replace compressor drive; if supply high/low customer to have supply fixed.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
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