Hi

Thanks for the info. I will have a look at the Flue to-night for soot.

Your suggestion about a weak mixture might well be right, The fan was
wire-brushed and alot of muck was removed from it so it may well be
supplying more air at this stage.

The valve I talked about is part of the 'pump' which is mounted on the
end of the motor. The oil feed line comes in one side and there are
two hex-nuts on it. One of them is used to bleed the pump when I run
out of oil and I have an air lock. The other hex nut (about 10-12mm in
size) has a screw in its centre about 4mm with a screwdriver slot in
it. I took it out once and there is a small spring inside it so I
guess it is probably the oil pressure adjuster.

What should I do to fix a meak mixture? I will get the make and model
of the boiler also when I get home and post it later on to-night, I
think it is a Riello but I will check to make sure.

regards

MJW

"John" wrote in message ...
"Michael Walsh" wrote in message
om...
I had my central heating oil boiler serviced last year, it had a
bearing replaced in the motor.

Since then it seems to burning a 'rich mixure', i.e. there is a very
obvious kerosene smell from the exhaust. And the oil fill seems to be
used quicker.

The smell is not forced to be due to a rich mixture. Unlikely though it
sounds a weak mixture also creates smell in the exhaust gases. There is a
fairly narrow band in which the mixture is "correct". In this band the
efficiency peaks, outside it the efficiency falls off fairly rapidly. Rich
mixtures invariably leads to soot formation which manifests itself as
visible smoke and soot deposits around the flue discharge. Weak mixtures
smell sour and the excess air causes the heat produced to be swept through
the boiler and out of the flue too fast to be absorbed by the heat
exchanger. In both non-ideal cases the fuel usage goes up.

There is a mixture screw/valve in the side but when I tried to adjust
it the burner stops and refuses to start again of its own accord
unless I increase the mixture.

Depending on the screw it might be the pump pressure adjuster. Is it on the
burner casting or on the oil pump?


Is it the quantity of fuel or the lack of air? Or am I completely on
the wrong track.

See above. It may be pertinent that the burner motor had a new bearing
fitted as this would involve removal of the fan and cleaning off of the
blades during reassembly. This gives fan delivery performance improvement
and weaker mixture results.


I can't remember the burner model number but if it helps I can look it
up to-night.

It would be a help, together with the make and model of the boiler