boiler not firing up

[philbatty]

I have a four-year old system with a Potterton Statesman Utility oil-fired boiler. The boiler runs normally for around four hours from cold then refuses to fire up because the boiler thermostat remains operated. The boiler thermal trip does not operate. I have tested the thermostat and it appears ok. Radiators and water heating work normally although water feed to the boiler seems hotter than usual. Any suggestions?

 

[Whiter]

What is the problem? If stat has reached temp are the pipes to the boiler still hot, are the rads cold, has your room stat reached temp, does the circulating pump work when the system is hot?

 

[wilhelm]

change the boiler stat.
err not an order, a suggestion.

but....

is the boiler outside?

is the boiler low level discharge? (oooerr)

and has it got an fan over run?

 

[philbatty]

Whiter, thanks for your reply. After about four hours of running, ie; the boiler cycling on and off as normal, the radiators gradually get cold. The room stat operates, the pump runs but the boiler will not fire, there is no power to the burner because the boiler stat remains operated. I can get the boiler to fire by turning the stat up full but the problem recurs after a short time. When everything has cooled down overnight, the system works normally for another four hours. (I tested the boiler stat with a pan of water and a thermometer, it switched on and off at the correct temperatures. ) Before I change the boiler stat is there anything else that could be causing this problem?

Wilhelm, thanks for your reply.
The boiler is inside the house. Not low level discharge as far as I know. (I have the installation manual) the boiler does not have a fan or pump overrrun.

Phil

 

[kevplumb]

ahhhh

lurkio has come out of the shadows

yeah i will expect the usual obusive e mail

 

[wilhelm]

naturally

anyway im still trying to digest this problem, bought some sherry for xmas.....well its open now.

let me think on

 

[wilhelm]

i downloaded the manual, nope, no over run, and it looks like a manual re-set.... and you say it b'aint be tripped. so i dont think boiler is at fault


well if boiler dont fire, perhaps one of your motorised valves is......


ka poot.

 

[Whiter]

Try a new boiler stat or test the old one when the boiler won't switch on.