pilot light wont stay on, thorn apollo boiler

[paulgatecrash]

Hi i wonder if anybody can help me my pilot light wont stay on, i would like some ideas as to what may be causing the problem
i have an old thorn apollo that has been serviced regulary up until a year ago. we are planning to have a new combi boiler fitted to an extension due to be finished in the summer so i don't want to pay a large repair bill

 

[ChrisR]

Probably the thermocouple. Not expensive but not the most common type. Make sure that whoever you call brings one!

 

[Nestor_Kelebay]

Chris:

Perhaps you can answer a question for me. If a pilot light won't stay lit, and the thermocouple is suspected to be the problem, it seems to me that an easy way to confirm that would be to:
a) disconnecting the old thermocouple at the gas valve,
b) connecting the new thermocouple to the gas valve, and
c) heating the new thermocouple with a candle or butane lighter to see if the pilot will stay on then.

But, when I once suggested that on another board, I got hollared at by a guy who claimed to be a plumber who said what I was suggesting was both wrong and dangerous advice. At the time, I didn't dispute it because I thought there may be different kinds of gas valves that I wasn't aware of, but the more I think about it, the more I think that there was nothing wrong or dangerous about that advice. If the pilot light stays lit when heating another thermocouple with a candle, then that's confirmation that the old thermocouple is in need of replacement.

Can you explain to me what, if anything, was wrong or dangerous about that advice I gave?

 

[Nestor_Kelebay]

PaulGateCrash:

Scroll back to the posts in this forum that were posted almost a week ago (on or about February 4th, 2006) and look for a thread entitled "Solder Ring Tee valves/ joints" posted by psarinuk.

Read my post in that thread, and it will explain how a gas valve typically works. If you know how a gas valve works, it's easy to diagnose why the pilot light isn't staying lit or why a boiler or water heater isn't firing up.

 

[chrishutt]

Can you explain to me what, if anything, was wrong or dangerous about that advice I gave?

Nothing terribly wrong in principle, providing you know exactly what your doing, but many don't. Surely it's safer to fit the new thermocouple in the correct way so it's heated by the pilot light. Also the test you suggest doesn't prove a fault with the old thermocouple. The problem could be lack of pilot flame impingement on the thermocouple.

There is also the issue of encouraging non-competent people to carry out gas work. As you know the thermocouple is an important safety device to prevent the release of large volumes of gas without controlled ignition (from the pilot light). Think what might happen if your suggestion was taken up by someone who didn't understand the risks.

 

[paulgatecrash]

Hi thanks for your help. a plumber came round to day and fitted a new thermocouple unfortunately that did not do the trick so he is going to ring me with a price for a new gas valve on monday

 

[bab]

one does expect he ruled out the over heat stat & terminals before changing the valve.

 

[Paul Barker]

let's hope so. Probably did though, just the poster doesn't understand these concepts so wouldn't think to mention, or does understand but omited to mention. Very hard without a crystal ball to know.

On that bopiler I would fit a new ohstat and leeeds as a matter of course and probably new high and low limit stats. Don't care if it is due for replacement this summer that's plenty of time to pay for those few cheap parts on a knackered old boiler.

As far as the gas valve goes, if it's only 4600a or c I would probably change it, but if it's one of the more expensive ones I'd be looking at the new boiler right away but obviously would have to find alternative location to an extension which doesn't exist..

 

[chrishutt]

Paul, I know I ought to know this, but what is the difference between the 4600 A and C gas valves?

 

[Paul Barker]

The c is slow ignition main burner, a is full on right away.

 

[chrishutt]

Thanks, I remember now (honest).

 

[brumylad]

the gas valves for this boiler are available cheap (£20) on ebay.

This boiler will work with a universal thermocouple but that means the overheat stat will no longer fuction, this is pottentially damgerous.

 

[Paul Barker]

Well why the hell did you mention it you idiot. You could now be responsible for an explosion, maybe a death.