6242 on a Worcester Bosch Bosch Compress 5800i AW: Alarm: safety temperature limiter FE on electric booster heater has tripped
Short answer
On a Worcester Bosch heat pump, 6242 means: Alarm: safety temperature limiter FE on electric booster heater has tripped. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Alarm: safety temperature limiter FE on electric booster heater has tripped.
Part involved: booster heater limiter FE.
When it shows: Alarm: safety temperature limiter FE on electric booster heater has tripped.
Likely causes:
- Booster heater overheat protection tripped.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: no.
Manual reset: Reset/acknowledge via UI 800 fault menu after cause removed.
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 heating system pressure gauge reading (Bosch guidance is typically 1-2 bar when cold); report low pressure to your installer.
What the engineer will check
- Check circulation pumps and system pressure; vent system.
Who to ask for: heat pump installer / electrician.
Certification: Electrical work to BS 7671 by competent person.
What you might notice
Sources
- Installationsanleitung Bedienfeld UI 800 (Luft-Wasser-Wärmepumpe) 6721833375 ↗ · 6721833375 (2023/09) DE, AT, CH, LU · page 22 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026