In an earlier contribution to this discussion,
steve wrote:

Set Square/Ed,

Thanks for your replies.

I've tried turning the temperature knob right down and up again but
the boiler still doesn't fire up.

As for the pump, I was assuming the pump was working because when the
boiler is running, all the radiators get hot (even the ones furthest
away start to get warm). However, I've now removed the bleed cap and
I can see the shaft moving round, though I guess it could still be a
detached impellor. I could turn the water flow off around the pump
and take it apart to actually check it's working correctly.

Not sure whether this is normal but when I first opened the bleed
valve it seemed like air was being sucked into the system. After a
few seconds though water started to drip out slowly.

Tonight I've ruled out the controls by bypassing the room thermostat
and hard wiring the main switch.

Also, when I first tried the boiler tonight I set the boiler stat to
it's lowest setting to try avoid it over-heating. It cut off after
the usual 5 minutes or so. I then reset the controls and turned the
stat up to max and the boiler still didn't fire up. Also, you can
hear the stat click and it's not even as far as the first setting,
which makes me think it's not actually overheating - or the stat
still isn't working - maybe I was sold a faulty one?!

So if the pump is working what else could be causing the lack of flow?
Could it be a seriously corroded heat exchanger. I'm assuming
there's no air lock or blockage as I've done a full drain and the
entire system is now refilled - is that a safe assumption?.

If the flow is ok, could it be a faulty over-heat stat? Unfortunately
I don't have a manual for the boiler so can't find out how you'd go
about replacing it. I've checked Baxi's web site and they don't have
manuals for their older boilers. Would this even be a serviceable
component?

Thanks again,
Steve


What sort of control valve does your system have. Is it a 3-port
mid-position valve to direct the water from the boiler either to the HW
circuit or the CH circuit or both together? Is there also a
thermostat on the hot water cylinder? What is that set at?

When the boiler fails to fire, is the pump still running? What do you
actually have to do to get the boiler to fire again? [You mentioned turning
the controls off and on. *Which* controls?]
Does the boiler have a reset button which has to be pressed in to make it
work again?
--
Cheers,
Set Square
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