"Ed Sirett" wrote in message
news
On Wed, 11 Jan 2006 14:32:54 +0000, Andy Hall wrote:
On 11 Jan 2006 02:04:09 -0800, "Bal" wrote:
I have checked the flue, all is clean, clear and the fumes are coming
out as normal.
OK.
If you are still getting the main burner and pilot cutting out after
having replaced the thermocouple (but it has improved), then the only
things left are the overheat thermostat (I think you had a suggestion
on how to test that) or the gas valve.
The thermostat would be pretty cheap I would have thought. By the
time you get to a new gas valve I'd start to wonder if it's worth it
in a boiler of this age and whether replacement would make more
economic sense.
I'm still concerned by the flame colour though. It would be a very
good idea to get the flue gas composition checked for carbon monoxide.
Realistically, that is a professional job since flue gas analysers
cost around £200+
The main causes for the OPs problems would be.
1) Lack of primary flow leading to over heating and shutdown.
2) A poor connection on the overheat stat that is set off by a slight rise
in temp.
3) A duff overheat stat.
N.B.
If the flames are yellow like a candle stop using this appliance, even
though it is a room sealed appliance.
I'm wondering now if we are dealing with a semi blocked heat exchanger which
is allowing some of the products of combustion to clear (hence heat comes
out of the flue) but filling the casing with burnt gases which then smother
the flame and pilot. I'd (very carefully and with one hand on the switch)
try choosing a day when wind conditions don't blow back into the balanced
flue and fire up without the outer case fitted to be able to say with
confidence that products are clearing "through" the finning of the heat
exchanger. I have in the past had problems with an Ideal Elan where the fins
had become restricted and the flames "filled" the combustion chamber and
licked out under the edge of the chamber. (In this case the solder on the
wires to the overheat stat actually melted off and cut the flames/gas)