Glow-worm Energy System fault S.42
Flue non-return flap closed
Gas boilerWhat it means
Status indicates the flue non-return flap is in the closed position.
Likely causes
- Flue non-return flap stuck or closed
- Incorrectly installed flue without sufficient fall can cause condensate to pool, leading to flue blockage or boiler faults
- Leak in the flue system
- Flue gas recirculation in extended flue gas installations
Where to start
- Check flue non-return flap operation
- Measure CO (ppm) and CO2 (%) at max rate and calculate CO/CO2 ratio
- Measure CO (ppm) and CO2 (%) at min rate and calculate CO/CO2 ratio
The full answer, free
- 12 more checks in order
- The readings and component tests from the manual
- How to put it right, step by step
- The manual page for this fault (page 50), right under the answer
Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.
From the Glow-worm manual for the Energy System. Check the model on the data plate before you order parts.
Other Glow-worm Energy System fault codes
- D.14Operating mode of the modulating pump
- F.00Flow temperature sensor fault
- F.01Return temperature sensor fault
- F.10Short circuit: flow temperature sensor
- F.11Short circuit: return temperature sensor
- F.22Safety shutdown: water deficiency in the boiler
- F.23Safety shutdown: temperature spread too great (NTC1/NTC2)
- F.24Safety shutdown: temperature rise too fast
- F.25Safety shutdown: flue gas temperature too high
- F.49EBUS fault: voltage too low
- F.61Fault: gas valve assembly control
- F.62Fault: gas valve switch-off control
- F.70Invalid product code (DSN)
- F.77Fault: condensate or smoke
- F.88Fault: gas valve assembly
- F.89Fault: pump
- S.53Product in waiting period / operating block function due to water deficiency...
- S.54Waiting period: water deficiency in the circuit (flow/return spread too large)