Boiler PIlot light goes out during night...consistently

[slimwallet]

Its a fairly old Concord CX boiler and typical experience is in the morning pilot light is out. Re-light boiler which is sometimes a little tricky to get going ....usually 2 or 3 attempts. Very occasionally it will go out after 5 minutes or so but usually is fine for whole of the day through to evening.

Go to bed and wake up with no heating as pilot out. We have had 3 new thermocouples in last two months explained as first being failed, second being faulty and now on third but still no difference so starting to lose confidence in the fitter. I do know that the thermocouples that have been fitted were apparently "generic replacements" and not Concord brand. Is that important?

Any suggestions gratefully received.

MAny Thanks

 

[Boilerman2]

Get your service engineer to:
1) make sure the pilot is clean with a good blue flame which envelops the tip of the thermocouple.

2) check the electrical resistance of the overheat interupter and overheat thermostat

3) check the power unit on the gas control valve (Assuming it's a V4400C)
if it is a V4600c the power unit is not replaceable and a new gas control may be required.

The above advice is for your GAS ENGINEER only it is NOT DIY ADVICE!!

 

[Agile]

You may intend that as advice for a professional in which case it should only be in the CC. Not in the open forum where DIYers will use it and possibly the OP as well.

In any case this is such basic work on a very basic boiler that any boiler engineer should not have any problem with it. Not even Namsag!

Tony

 

[slimwallet]

MAny thanks for the advice. I will pas it on although I'm not sure I will use the same chap anymore as it sounds as though other checks should have been done.

I have a glimmer of understanding how these things work but what never makes sense as why it only happens overnight ????

Boiler cuts in and out throughout day with no problems so surely if overheat thermostat or gas control valve was a problem it should also happen during daytime on occasions aswell!

 

[FiremanT]

Boiler cuts in and out throughout day with no problems so surely if overheat thermostat or gas control valve was a problem it should also happen during daytime on occasions aswell![/quote]

That does seem odd. A bit of a long shot, but is there anything like a washing machine set to work overnight in the locale?

If so, the vibrations cause cause a loose connection, say on the t'couple / gas valve to give way It only takes a split second of interuption to kill the pilot. I don't think theis boiler would have an OH stat or interuptor, but if it does, the same could apply.

By the way, have you spoken to your fitter? What does he say? It may be a little unfair to condemn him at this stage, as, if the pilot is clean, it couldn't be argued that he was wrong to change the 1st t/c. Changin a 2nd without testing for other reasons could be considered a little idle, but it still isn't a hanging offence, and things do go wrong. Given the cheap nature of a t/c it is no disaster. Clearly a 3rd time would be a little silly!

Regarding the source of the t/c: most original ones on older boilers were Honeywell Q309A. A lot of fitters use "universal" replacements which are as cheap as chips, and last for about the same time. I always use genuine Honeywells, where available, and, bizzarely, they don't cost a great deal more! I don't think there was actually a specific concorde t/c, it was probably originally a HW.

 

[slimwallet]

Thanks,

THere is nothing in vicinity that runs during night..not even a cat to cuddle up to it so it is a bit of a mystery

Maybe I am being a bit premature on condeming my chap and I assume from the comments that a universal T/C is not likely to be the issue.

In my paranoia I did wonder if pilot died due to a dip in mains pressure when everbody's boiler cuts in a roughly the same time on a morning but perhaps that is a bit far fetched!!

 

[slimwallet]

I thought I would post an update for all who followed or posted on this thread.

When boiler was hot wriggling both leads to overheat stat caused no problems at all.

When totally stone cold a wriggle on one of the leads caused pilot to trip as signal to gas control valve was lost. This was repeatable time and time again.

So it seems that expansion when warm gave a good connection but sometime during night connection was intermittently lost as spade connector cooled.

Connections now really tightened and boiler running perfectly.

Thanks to all those who contributed

 

[namsag]

OP sorry for hijack just replying to a previous comment.

Agile.
The day a CC ariel repairman gets even half as good as me is the day i will start worrying.
For someone who has to ask how to hang a boiler on a wall to try and take the pi55 is so fekin funny.
I have forgotten more than you will ever know.