Vaillant Boiler 221 pilot light keeps going out !

[paul55]

Got a combi boiler Model No VCW GB 221

woking fine up to yesterday problems started after i tried the central heating after the long summer break,

worked fine for coulpe of hours then the next day no hot water ,cause pilot light went out for some reason !

water pressure was at 0 so i got it up to 1.5 bars

had air in the rads took that out .

put the pressure up to about 1.75bars

Now cant get the pilot to say on for long .

takes ages to get it on seems to want to go out like theirs no gas !

once the pilot light is on i turn on the tap for hot water it seems i have to turn the tap more now than b4 to fire up the boiler .

the boiler does fire up the hot water does come but after about 30 - 1 min

a noise goes TOCK! inside the boiler and the pilot light goes off!

happend all the time even when i switch on the rads after a min or so TOCK! and the pilot goes off with !

any idea's what i should be looking at ? what is that noise!

 

[Gees]

Looks like the thermocouple is dying ( it holds the gas valve open with a current provided by the pilot light)
As for the slow start on hot water .. sounds like my old pal the divertor valve

( I am NOT a heating engineer)

 

[paul55]

yeah thx for that but what about once i get the pilot light working the

boiler works for about a minute !

what casusing the Tock noise then the pilot light goes off!

 

[breezer]

I am not a plumber or heating engineer, but perhaps as you say there is a tock noise then the pilot light goes out, that may be the gas valve closing down (because of thermo couple) so no gas, pilot light goes out

 

[Gees]

The noise you hear as Breezer suggests is probably the gas valve closing. Its usually a spring loaded rubber covered steel disc about 1 inch in diameter ( its inside the gas valve ) when the electromagnet lets go the valve closes very quickly ( with a sort of PLOP ). As the tc wears out sometimes it will provide enough current to hold the valve open but when it gets very hot it may be breaking down.

First thing to do is replace the tc and see what happens..


Cheers

 

[paul55]

im gonna clean the tc see if that works i let u guys know how i get on for future ref

 

[paul55]

ok just open it up cause the my regular plumber's at a wedding and cant come round till monday

so i open up the silver cover just a single screw and to clips at the bottom

can get really good access to the tc bits and did'nt wanna open up the nuts and bolts as my lever of expertise in this field is no that clever so i shaked it about a bit undon one nut and clean the pipe not sure which one it is ie gas or electric ! hoover up in there as there was a lot of dead spiders inside god know's why ! lol and put it all back so far its been working for about 30 mins where as b4 would not work for more than i minute so fingers crossed!

 

[paul55]

it think its done the job

2 days no problems

thx to all who help much appreciated guys thx's