Biasi 24 s combi boiler. The problem is the central heating comes on randomly even though the thermostat for heating is turned right down, the time clock is in the off position, and there is no room stat fitted. What is wrong with this boiler?

Alwyn Crowe, May 2007

Biasi SG3 with riello 40 gun fires constantly for extended periods of time. heat is working fine in the house just doesn't seem right. Also there is a slight smell oil fumes in the basement near it.

TimD, April 2012

hi all biasi 24s model, boiler is in off poisition, and heating switches on. i put the thermostat to summer settings and it still switches on, turned the switch to winter settings and still switches on.had the dhw microswitch changed a month ago and the diaphram.
help

stuart, October 2009

Its almostly certainly the second option.

The DHW gland will have leaked into the microswitch making the boiler think there is a demand for heat.

The gland and the switch will need to be replaced but that involves removing the gas valve so is a job for a CORGI.

Tony Glazier, August 2007

If it's a prisma 24s the two most likely options are ;
The central heating thermistor is faulty and putting the boiler on for frost protection.,
Or the domestic hot water microswitch is keeping the boiler running on hot water even though the taps are off.
Try putting the selector switch to hot water only. This should stop it if it is the first option.

T.H.S, May 2007