CH Problem **UPDATE**

[Alan1]

Hi,
After the last post i've moved my pump to a higher location and the vent pipe is now the at the absolute top of the system, so the air issue is sorted.
But this has now shown a clear problem in the boiler. Its a halsted blenheim 15/30, this is what it does: heats one cycle, reaches the thermostat temp then drops to pilot light, then 30 seconds later the boiler cutts off with a clunk noise.

There is an overheat shut off on this model but this routine occurs regardless of temp.. (i've tried it at virutualy no heat)

So my question now is which part the the boiler do i need to replace, overheat thermostat?

I've got a vented system with 1 pump and this boiler is used only for the Central Heating.. I've changed the thermostat on the boiler within the last week.. And the thermocouple..

 

[MANDATE]

I'm fairly sure you may find the advice you want from www.halsteadboilers.co.uk

 

[COG]

it sound as if your overheat stat is tripptng out, you cant run the boiler with virtually no heat, when that burner is lit on min its still alot of energy. there is more chance that the stat is picking up an overheat problem,air ,sticking pump etc.an overheat stat will tend to fail and stay off,the type you have that is,

 

[Alan1]

so u think there is another problem in the system causing the overheat stat to trip the boiler?,

I spoke to halsted and the guy said it is likly to be the 'spilt wire/interupter lead' that has a fault.. think thats likely?

(its the wire that connects the overheat stat to the thermostat/and electic block)
Though i think i'll just replace the overheat stat and the gas control valve if this does'nt work.
Even if there is an amount of air in the line or sludge in the system i find it hard to belive that the boiler will run 1 full cycle then power down before cutting out if the line has air..
I would expect a less exact behavor or routeen for this problem.
A boiler fault sounds more likely do you not agree?

 

[COG]

Rather than just swapping parts ,get yourself a hand held stat with surface probe or flying lead and see what temp you get at the limit stat, you can get one for around £20. the leads that Halstead mentioned do tend to get poor as they get hard with the heat it and age so it would be no harm to change given the low cost, but a system fault is far more suspect from what you have said than a gas valve dropping out ,again you can test it if you have a multi meter with mili volts settings. . keep in mind that most company tech service eng that answer the phone work only of drawings etc and have never been on site to fix a boiler so are limited with system faults,and usually look for a component fault as thats all they have to go on (i used to work with some,never again). excuse spelling and grammar having a bad few days