pilot going out

[charlie]

Hi everyone am new to forum.

Have got a Baxi solo rs 50 boiler were pilot goes out as soon as i remove finger off gas valve.

The pilot is burning ok over thermocouple....
Have changed the thermocouple but still have problem.....
So changed gas control valve but still have problem.....

Please help cant think of any thing else to do.

p.s. the system is gravity fed so over heat cut-out is shorted

 

[stevetheplumber]

Hi everyone am new to forum.

Have got a Baxi solo rs 50 boiler were pilot goes out as soon as i remove finger off gas valve.

The pilot is burning ok over thermocouple....
Have changed the thermocouple but still have problem.....
So changed gas control valve but still have problem.....

Please help cant think of any thing else to do.

p.s. the system is gravity fed so over heat cut-out is shorted

youve changed all the parts that could cause this either one is faulty or youve done something wrong
you can test the thermocouple with a multimeter but i cant remeber what voltage it should produce im sure baxi will tell you
check the link on the overheat hasnt failed in some way

 

[newbie1]

as steve said normally this would be the thermocouple then gas valve but i wld def check the thermocouple again
were the parts you replaced it with new as normally the problems are nearly allways soved by a new thermocouple
is this youre own boiler

 

[Bernie2]

Try bridging out boiler over heat stat. Some of them act as an interrupter with a connection underneath the thermocouple connection on the gas valve.

The voltage for a thermocouple is usually about 10 - 40 millivolts. Take out connect to the inner and outer and then heat up thermocouple to get reading.

You can get drop testers for thermocouples as well.

They fit on the end, you then heat up the burner end and hold in the drop out on the drop tester. If it holds in for 30 secs or so, the thermocouple is okay.

They where about a tenner from HRP.

 

[charlie]

Thanks for all replies.

The overheat stat is already linked out as manufactures instuction as it is gravity fed system.

Will try testing with voltmeter as this sounds good idea of proof of working of thermocouple.

Hope it is a duff thermocouple i've bought so i can get up and running again as i can't think of what else it might be.

Will keep everyone informed.

Forgot to ask .....as anyone bought a duff thermocouple before ????

On the new one it is flattened for about 2 inch of its length with what looks like a stamp of some sort ???

Is this normal ??

Try bridging out boiler over heat stat. Some of them act as an interrupter with a connection underneath the thermocouple connection on the gas valve.

The voltage for a thermocouple is usually about 10 - 40 millivolts. Take out connect to the inner and outer and then heat up thermocouple to get reading.

You can get drop testers for thermocouples as well.

They fit on the end, you then heat up the burner end and hold in the drop out on the drop tester. If it holds in for 30 secs or so, the thermocouple is okay.

They where about a tenner from HRP.

to test do you mean 1 lead onto copper outer sheath + 1 lead on to the small bulb end which screws into the gas valve ??????

 

[Bernie2]

Yes! Link them up that way outer sheath and blob on end.

I assume you have tried the gas supply to the pilot for flow and the pilot injector for clear?

The only other easy thing is the overheat stat connections being clean and tight. I know you have bridged them out or piggybacked as the manual says, but they have to be tight not overly tight but making good electrical contact.

 

[charlie]

gas pressure to valve 26mb .
fitted new injector.
connections secure.

Am at a total loss all parts involved have been changed for new but pilot still going out.
Anymore suggestions please as it is a total baffle to me .

 

[Plouasne]

Over pressure (26mb at valve) with flame lift off ?, I believe that the working pressure for natural gas in the UK should be 20mb, its 20 years or more that I have worked on gas in the UK, so could be wrong

 

[newbie1]

26mb is that standing pressure at inlet with appliance off if so not a huge problem as the regulator should adjust that so working pressure should be anywhere in the 19-23mb range with appliance running and as per manufacturer for burner pressure

 

[charlie]

pressure measured at test point on valve.
appliance off as that is my problem cant get it to light as pilot wont stay on !!

again help please anyone am really desperate to get this thing sorted.....

 

[Bernie2]

Test inlet and outlet pressures on gas valve? A supply pressure is usually about 20mbar not 26mbar. Perhaps the meter governor is stuck? But the appliance should govern that down if the gas valve is set right for the appliance. Have they given you the right replacement gas valve?

 

[smoggs03]

i had this on my parents what i found was the connection between thermocouple and gas valve was dodgy (blue plastic type thing) any way managed to temp it with foil by packing it out !!

 

[migoplumber]

as smoggs says the blue thingy with a yellow wire often causes a problem, do you have one?

never bought a dodgy thermocouple ever, however i have bought 4 dodgy gas valves, if that was your original problem, and you have a dodgy one, that would also explain why your stuck!!

shaun

 

[Puddle]

back to basics,what gas valve is fitted is it the gray push knob or the green push knob
forget gas pressures,you should be able to fit thermocouple to gas valve in your hand, heat thermocouple tip with blow lamp while pressing in gas valve knob,release after 25 secs and valve will stay open,I have had faulty thermocouples recently,you can check voltage but above test easier for many,am concerned about this high limit thermostate being wired though,if not needed bypass at gas valve and fit thermocouple straight to gas valve power pack,as you say pilot goes out after gas valve knob released ,if green controls could be you are pressing side ways instead of straight down,this will turn pilot out

 

[Bernie2]

Yes Puddle I was puzzled about cutting the over heat stat out. I checked it in the manual and it does say that. But I am still puzzled as to why?

I can guess of course that the higher temperatures required before convection starts properly in a gravity system may have something to do with it. But I would have thought they would have taken that into account and put a higher setting overheat stat in, not bridge it out.

 

[charlie]

Have tried anther thermocouple and problem remains.
can,t think of a way to test valve any further without buying yet another valve at a cost of approx. 60 pound as i'm sure they will not give me a swop/replacement at the suppliers as i have no proof they have sold me a faulty one.

 

[Bernie2]

Funnily enough you don't usually have any trouble with swops usually.
The shop have to prove it was working when they sold it to you. In practice they usually just return them to the makers and I think the makers in this instance are Honeywell. If Honeywell say its okay then you know its not the gas valve.

 

[stevetheplumber]

Yes Puddle I was puzzled about cutting the over heat stat out. I checked it in the manual and it does say that. But I am still puzzled as to why?

I can guess of course that the higher temperatures required before convection starts properly in a gravity system may have something to do with it. But I would have thought they would have taken that into account and put a higher setting overheat stat in, not bridge it out.

the overheat stat would have been fitted as standard to allow using the boiler on a sealed system but not necessary on a gravity system as its open vented
on some boilers if you wanted to use a sealed system you had to buy a kit to add an overheat stat as sealed systems became more common they include the stat but we had a lot of problems with overheat faults on gravity setups and the cure was to bridge out the unnecessary stat

pressure measured at test point on valve.
appliance off as that is my problem cant get it to light as pilot wont stay on !!

again help please anyone am really desperate to get this thing sorted.....

as i said befor youve changed everything thats involved in the pilot chain providing the pilot flame is good and warming the thermocouple. To test the gas valve cheaply get a new thermocouple screw it DIRECTLY into the gas valve and with the gas to appliance turned of and the thermocouple hanging down warm it with a blowlamp and you will feel if the gas valve is holding in when you realese the button

pressure measured at test point on valve.
appliance off as that is my problem cant get it to light as pilot wont stay on !!

again help please anyone am really desperate to get this thing sorted.....

i said befor youve changed everything thats involved in the pilot chain providing the pilot flame is good and warming the thermocouple. To test the gas valve cheaply get a new thermocouple screw it DIRECTLY into the gas valve and with the gas to appliance turned of and the thermocouple hanging down warm it with a blowlamp and you will feel if the gas valve is holding in when you realese the button
my bet on this would as has been said the overheat test it with a meter for continuity by screwing the thermo diretly into the gas valve you can eliminate this