apollo pilot light wont stay lit!!!

[Notebook64]

apollo boiler - noticed pump running or noide, but no hot water - heating.
Pilot light out, restarted but when relaesing valve button for lighting it went out. Changed pilot light cover/jet as badly worn. Also heated thermocouple and getting about 25mV going to the valve. Thermostat switch high low makes a swithching nois, and also electrcity turns on noise - pump?
However as I relaese the valve, it goes out at the last second. Any help appreciated.

thanks

 

[wilder74]

Id say overheat stat,if youve changed t/c,but could be gas valve,are you rgi,so you could link the o/h out

 

[Notebook64]

Id say overheat stat,if youve changed t/c,but could be gas valve,are you rgi,so you could link the o/h out

Not rgi. Electronics maintenance tech.
I havent changed the thermocouple yet. It has 2 wires mid way to the valve that connect to a stat. how does this work as appear to connect to the outer copper of the tcouple? What does it do? normally open or closed? Is this the oh?

 

[gas4you]

The overheat, when tripped will cut the continuity in the thermocouple circuit, so the pilot will go out.

Should really be getting an RGI in as it is a safety device for your boiler.

 

[andytheplumber]

Its the thermocoupler interrupter.

 

[Agile]

Your 25 mV would have been o/c !

You need to measure the on load voltage from the TC both before and AFTER the o/h stat!

The on load voltage is uaually about 11-13 mV and aftert eh o/h stat often down to 9-10 mV. The gas valve usually needs about 7-9 mV to stay on reliably!

Tony

 

[Notebook64]

Your 25 mV would have been o/c !

You need to measure the on load voltage from the TC both before and AFTER the o/h stat!

The on load voltage is uaually about 11-13 mV and aftert eh o/h stat often down to 9-10 mV. The gas valve usually needs about 7-9 mV to stay on reliably!

Tony

Hi tony
oc? open circuit?
Is the stat normaly closed or open?
To measure this I would have to remove the cover and light the pilot light. Then measure the voltage by removing the end of the thermocouple from the gas valve. This would give me one reading. Where do i take the other? On the top of the boiler on one side of the stat?

Also
gas valve
what is the pot on it going -ve to +ve? amount of gas? oxygen?

thanks
Nick

 

[Notebook64]

just checked the stat inline with the thermocouple and its short circuit/closed, so its not that. Also lloked at the stat mounted in the wall of the unit. I take it that this is the high low? anyway it also is short circiut.
Is this correct?

Thanks

 

[Notebook64]

Anyone give some more input?

Thanks

 

[superdupergasman]

25mV sounds very high for a thermocpl, usually 15mV but anyway
get a new one and try it.

The over heat stat sould be a dead short, know as an interupter type, when over heated (around 100oC) it will become open circuit and cut off
voltage to the Gas valve electromagnet.

It can be only 3 components T/C, o/h stat or Gas valve, get a new T/C and try it....only a fiver so no big deal, your stats fine so if not your t/c your into a gas valve.

 

[Rob]

Yeah, CHANGE the thermocouple and OH stat.

 

[Notebook64]

thanks guys
had trouble buying the pilot light cap jobby as not corgi registered. Can these be bought online, or isnt this a protected partif you see what I mean.

Thanks
Nick