Hi,

In the process of clearing a house (deceased relative) and decided the
boiler should have a routine service as it'll be running unattended to keep
some background heat whilst the building is vacant, and winter approacheth.

Long story short - did the "right thing"[1] and booked in a CORGI fitter.

After he cleaned the boiler, he wanted to fire it up to do the smoke test.
Problem is that it wouldn't fire the main burner. After some messing about,
I proved for him that there was in fact 240V reaching the solenoid gas
valve module

The pilot was on and holding in at this stage.

The control gear design is simple - switched-live from heating
controller/stats come in. That goes via a mechanical boiler stat. That then
presents to the solenoid valve module that also takes in the pilot light
thermocouple and provides controlled gas feeds to the main burner and the
pilot. Old style system, no visible electronics (maybe a bit hidden in the
valve module, or not).

When I carefully removed the live connection from the valve module and
replaced it there was a definite "clunk" coming from the unit which I took
to be a valve solenoid.

Weird thing was that the main burner failed to start as a result of
the "clunk". Weirder still was that after about 2 minutes, the burner did
eventually light up and ran correctly on full flame. Upon turning the
boiler circuit off, it took about 1 minute before the main burner shut
down. This time lag for starting and stopping appeared to be consistent and
repeatable.

******

Question: is this time delay between electrical power applied and gas being
switched on a feature of some types of valve module? Or is it indicative
that the module is on the way out? Sticky bits betwixt the solenoid and the
valve perhaps?

******

Before anyone asks, I did ask the fitter and he said he didn't know due to
lack of experience with that type of boiler. Which seems odd as it's not
exactly an old or uncommon model.

Many thanks for any opinions on the valve (or otherwise!)

Cheers

Tim


[1] Nice enough bloke, shame about apparent lack of experience and ability
to undertake basic electrical fault finding, considering his hourly rate.
I'll do the sodding job myself next time.