softstarter on a Worcester Bosch Greenstore LECP ground source heat pump: Soft starter alarm (red LED flashes 2/3/4/5)
Short answer
On a Worcester Bosch heat pump, softstarter means: Soft starter alarm (red LED flashes 2/3/4/5). 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: Soft starter alarm (red LED flashes 2/3/4/5).
Part involved: soft starter.
When it shows: 2 flashes undervoltage <190 VAC (auto reset 5 min); 3 overcurrent during start-up >80 A for 1 s (auto reset); 4 relay protection (user action/possible replacement); 5 incomplete ramp (auto reset). Type 3 indicates compressor fault.
Likely causes:
- 2 flashes undervoltage <190 VAC (auto reset 5 min); 3 overcurrent during start-up >80 A for 1 s (auto reset); 4 relay protection (user action/possible replacement); 5 incomplete ramp (auto reset). Type 3 indicates compressor fault.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: yes.
Manual reset: Auto reset with 5 min recovery (2,3,5); unit replacement if 4/5 repeat.
What you can check
- Read and note the full alarm text and category letter 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
- Diagnose per chapter 21: 2 flashes undervoltage <190 VAC (auto reset 5 min); 3 overcurrent during start-up >80 A for 1 s (auto reset); 4 relay protection (user action/possible replacement); 5 incomplete ramp (auto reset). Type 3 indicates compressor fault.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
What you might notice
Sources
- Installation, Commissioning and Servicing Instructions Worcester Greenstore LECP GSHP (System/Combi 6-11 kW) ↗ · 6 720 806 768 (2013/02) · page 58 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026