DIY Doctor UK DIY Forums

Hi

I have just had the boiler serviced and the pilot light took ages to light then after a while would go out, so i replaced the thermocouple and lights easier now but after the heating been on for a while then switched off after a while the pilot light goes out, i am a bit puzzled as to what is happening.

Anyone had this prob or does anyone have any ideas what it could be.


Thanks

hi you do not say what make of boiler it is, and this is important, because a lot of boilers had copper low content heat exchangers and it sounds like you have a common problem that happens with these as they get older, they tend to get corroded inside so when the heating is on its ok,, but when the heating goes off the latent heat in the heat exchanger has to dissipate out this is normally via the pump overun stat that runs the pump for 3/4 mins after the boiler has turned off,
However sometimes system were wired up from the start and the pump was never wired direct to the boiler, if not this causes the corrosion insde ,, So back to the problem the water left in the heat exchanger now becomes higher than the temp of the overheat stat which in turn is coupled with and interupter which for safteys sake knocks out the pilot light
So i should get the R G I to check to see if the pump overun stat is working or if the pump is wired correctly to the boiler

hope this helps


mick

Does the pilot flame look good and strong (blue) ?
If not the pilot may need cleaning and possibly a new injector.

Is the thermocouple fitted properly, tightened onto gas valve.

htg

hi
the flame is blue at base and yellow at top its about 2.5".

Should the thermo sit in the pilot or should there be a small gap between. Mine has a 4 mm gap and am wondering whether this is to far so when there is draft hitting the flame away from the thermo it cools and turns off, is this possible.?

sorry, the gap between the thermo and pilot is about 1cm! is this normal?

The TC should sit in the pilot flame, this is what keeps the thermo-electric part of the gas valve open so there is gas to the pilot.

Get an RGI to repair.

htg

Hi Thanks for all your help..

I adjusted the TC closer to the pilot but could not adjust it so it sits right in it as it uses the same mounting and is a fixed distance. This has now solved the problem.

:D

I didn't say adjust the TC, the mounting for this will be fixed. It's the pilot flame at fault.

From the description the pilot seems to be yellow tipping - you need a RGI to check and repair.


htg