Roger Mills wrote:
On 16/04/2011 13:29, Nick wrote:
Boiler is Potterton 200K BTU. About 15 years old.
Conventional fully pumped vented system.
Installed and serviced annually by the same engineer.

Through the winter it had a problem. Heat output considerably down,
making
soot and noxious fumes. Boiler is located in a well vented external
boiler
room.

Engineer came out and diagnosed the gas control valve as being worn out.
Next visit he serviced the boiler, de-coked the heat exchanger,
dismantled
and cleaned the flue, fitted and adjusted the new gas valve. Left in
working
order.

The boiler is certainly running much better. Good blue flame and somewhat
quieter. Water output temp has risen gradually and continues to rise.

Problem is that it is still making soot in appreciable quantities.
Flakes up
to about 10mm across.
Have spoken to the engineer again and he is a bit stumped.

My only guesses are (1) the boiler is now working more efficiently and is
burning off residue from the H/E or (2) that the burner unit is worn,
burning improperly, and creating soot.

If (1) I hope the problem will go away, but it has now been 3 months.

Any ideas please?

Nick.



Soot usually comes from a yellow flame when there's not enough air to
burn the gas fully - but you say the flame is blue?

I know nothing about gas boilers, but a lot about fires,,and you are
right,,soot is bad combustion and the soot particles glow yellow hot and
that's what makes the flames yellow.

So it sounds as it the other theory - that its simply burning old ****
out - is the right one. You should see what comes out of a chimney if
you set one on fire. LOTS of soot!

The last guy to service my (oil) boiler had some sort of gas
analyser..presumably that's true of yer gas man, so if the combustion is
within spec, that's all you need to worry aboput..ultimately the soot
will burn away I guess.