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Category: UK Plumbing
Satisfied Customers: 3966
Experience:  NA
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Pilot light will not stay lit Engineer has replaced

Customer Question

Pilot light will not stay lit Engineer has replaced thermocouple checked electrics and replaced gas valve The boiler ran for a day but today same problem as the pitot light will not stay lit Boiler 20yrs old servowarm
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Submitted: 7 months ago.
Category: UK Plumbing
Expert:  NA replied 7 months ago.

Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Please provide all information I request as it makes it more difficult to troubleshoot something when I'm not there onsite. Essentially, you become my eyes and ears. Thanks for the opportunity to help. At the end of our dialog, you will have a chance to rate my service, but please wait until we are finished and you're satisfied you have all the information you need. Please be patient as many times we work with several customers at once.

I see none of our experts have picked up your question yet. Couple things: is the pilot flame strong, blue, and enveloping the last 3/8 inch of the thermocouple? Does the boiler have a good wind cap at the top of chimney outside?

Customer: replied 7 months ago.
Exhaust outlet to boiler is well capped. It has nothing to do with wind. The pilot light is lighting easily but after holding the button down for 60secs there is no gas supply as the light then goes out the flame is more blue than orange and is about 3/4inch high below the thermocouple
Expert:  NA replied 7 months ago.

So it sounds like it is a gas supply problem, then. Has regulator been checked?

Customer: replied 7 months ago.
Doubt if it is the regulator as the pilot light is lighting fine but not staying lit when released
Expert:  NA replied 7 months ago.

Unfortunately just stating "doubt if it's the regulator" is not getting us anywhere. We need to look at all the things that cause a pilot to go out and actually eliminate them one by one. Typically the most common reason a standing pilot goes out is a bad thermocouple or poor pilot flame. The output of the thermocouple can actually be measured using a meter and a thermocouple adapter. These should put out between 25-30 millivolts. The next thing if this checks out OK is a bad gas valve. Sounds like that's been replace, although it's always possible to get a defective valve. Low pressure or gas pressure problems can also cause pilot outages. Finally if pilot goes out intermittently, a downdraft through the chimney can blow pilot out.

Customer: replied 7 months ago.
Thanks. Thermocouple and gas valve have been replaced. By bypassing the overheating reset switch and wiring the thermocouple direct to the gas valve the pilot light can be relit (trying to locate and replace cutout switch) BUT the pilot is going out when the boiler switches off overnight and has to be manually relit in the morning
Expert:  NA replied 7 months ago.

Could be blown out by wind coming down chimney, OR when boiler is lighting (or burner shuts down) could be doing it with such force it blows pilot out. Or, as I said, could be a pressure problem and this can be measured with a device called a manometer.

Expert:  NA replied 7 months ago.

Let me know if you have additional questions. Otherwise, good luck! Thanks for using Just Answer and please don't forget to rate my service as that's how experts get paid (thanks in advance for any bonus left). Otherwise experts work at their own time and expense. Feel free to post back with any more questions.

Expert:  NA replied 7 months ago.

Did you have additional questions on this?

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