wrote:

I have a system boiler abot 10 years old (non condensing). It is a Glowworm
complheat. I am getting condensation from the flue dripping down the wall and
staining the brickwork.

Any comments?

Check the return water temperature to the boiler when the heating is
running (and up to temperature). It ought to be about 70 on a
conventional boiler. If it is too low (i.e. less than 56 deg C) then
that will promote condensation of the flue gasses.

Is it serious?

Condensation in a non condencing boiler? Yup, can be. The condesate is
wet (obviously!) and mildly acidic. A combination that can rot the
inside of a boiler or heat exchanger in short order if left unchecked.

How do I stop it?

Re-balance the system (see FAQ), you may need to increase the pump speed
to prevent the water cooling too much per circuit. In particularly
tricky cases you may need a blending valve to mix a little hotter water
from the flow side of the boiler into the return to keep it above the
dew point.

How do I clean the bricks?

Are they just wet or actually stained?



--
Cheers,

John.

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Re-balance the system (see FAQ), you may need to increase the pump speed
to prevent the water cooling too much per circuit.

Also check that the flow temperature control isn't too low.

Christian.