Grant Boilerhouse fault 5
Boiler operating on overheat thermostat
Oil boilerWhat it means
Boiler is being controlled/tripped by the overheat thermostat, indicating a circulation or control fault.
Likely causes
- Faulty boiler thermostat
- No circulation
- Faulty circulating pump
- Air lock in system
- Debris, leaves, hair, fluff accumulation in air inlet cover and air damper
- Debris accumulation on fan impeller and fan housing
- Contamination in oil pump filter
- Air lock in pump
- Pump running dry causing bearing damage
Where to start
- Check circulating pump
- Check for air lock
- Holding the body of the Photodiode (NOT the cable), carefully pull it out of the burner and clean the sensor end
The full answer, free
- 48 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 48), right under the answer
Safety: Isolate oil and power before you touch the burner. Do a combustion test after any burner adjustment or part change. OFTEC (or equivalent) work only.
From the Grant manual for the Boilerhouse. Check the model on the data plate before you order parts.