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Worcester Bosch Greenstar RI Heat Only fault 8

MAX safety thermostat activated

Gas boiler

What it means

Blocking fault. Flue gas thermostat overheat or APS (air pressure switch) activated.

Likely causes

  1. Flue gas thermostat overheat
  2. APS activated

Where to start

  1. Check flue gas thermostat
  2. Check air pressure switch (APS) operation

The full answer, free

  • How to put it right, step by step
  • The manual page for this fault (page 54), right under the answer
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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 Worcester Bosch manual for the Greenstar RI Heat Only. Check the model on the data plate before you order parts.

Other Worcester Bosch Greenstar RI Heat Only fault codes