I have a Potterton Prima 40B conventional heat-only boiler that was installed in 1999. The pilot light goes out after the hot water comes on. It will stay on if the heating is on, but about 2 minutes after the hot water timer comes on, it goes out. I've had the thermocouple replaced.

I wanted to get some advice before I have to spend on a new boiler and its trimmings.


Hi, I now have a little more information. If I ignite the pilot, it will stay on. The controls are set to CH only with the HW off. The burner will come on to start the CH. If I then switch the HW on, after a couple of minutes the pilot goes out and the boiler will have to be reignited.

This morning I have tried it vice versa. CH off HW on. The boiler stays on. If I have both on at the same time it goes off.

Just to add, I left the CH controls to zero last night but on at the main control the pilot stayed on all night at that. I then turned the temp up on the heating this morning and the boiler went off, but I was able to reignite and it stayed on (until HW was turned on). I then turned the CH off and HW on and its still working.

  • Can you include a more clear description of the sequence of events? It sounds like the pilot is on, then the main burner comes on. The main burner shuts off, then 2 minutes later the pilot goes out. Is that correct? – Tester101 Aug 28 '15 at 19:29

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