The gas will not stay on to heat the radiators, however is fine with the hot water. When we switch the heating on the gas lights for few seconds and goes out, it then keeps trying to spark up but will not stay on long enough to heat the system. When using the hot water the gas lights and stays on all the time until you stop drawing from it. What is the fault?

Rodney Palmer, April 2008

when heating is on pressure drops and water coming out of overflow pipe

barry baker, December 2009

works on heating but will not fire up on hot water

mitch, October 2009

heating side of boiler works fine but dose not fire up on hot water demand

mitch, October 2009

The most likely cause of this problem is the CH flow switch not detecting enough flow. Check the switch (red wires) which should close when there is flow. There may be some contamination stopping it operating or it may have failed. Try removing it and cleaning, otherwise change it. It is not the same as the DHW switch although it looks the same!

keith knutton, May 2008

cant remember what set up these run but most boilers tend to run at full gas rate for domestic hot water and for heating they fire up on high then go to low flame. example on modureg low rate can work its way out and burner will extinguish as it tries to go to low. other possibility faulty thermistor on ch circuit. hard to say when you aint there tho sorry.

z, April 2008