"Stoney" wrote in message
...
This my third go at getting somewhere with my ailing boiler.
The problem now appears to be that the thermocouple is failing at high
temperatures. So it will stay on all night but it will stop working after
the boiler runs for 10 minuites or so.
Does anyone have any experience of this?
I have put in a new thermocouple but the same thing is happening.

It could be that this is what it's meant to do: some open-flued appliances
(generally gas fires, but maybe some boilers?) have a 'vitiation' device -
an arrangement for detecting that oxygen levels in the air being drawn in
for combustion are dangerously low, and shutting down the appliance. If you
fix this 'problem' it could be the last one you'll fix :-|

Is the boiler in an enclosure of some sort, and if so does it have
any/enough ventilation? Are the main burner flames nice and regular shaped
and blue or straggly and yellow? I would not expect vitiation (depletion of
oxygen) to occur in any reasonable-size room within 10 minutes but there are
some unusual combinations of the location of the boiler and its flue
relative to the natural airflow within the house, which can cause combusion
products not to discharge up the flue but to hang around and starve the
boiler (and cause carbon monoxide production!).



--
John Stumbles
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The most dangerous component in a car is the nut that holds the steering
wheel