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?

Why would a gas boiler make soot?

Apr 16, 2011 Last reply: 4 years ago 23 Replies

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danny 4 years ago

Not true. Lack of make up air can cause issues with incomplete combustion and high carbon monoxide levels. Gases can't vent out if there's no air to replace them

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Fredxx 4 years ago

Please read this:

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replying to a 10 year old thread to a boiler that's already 15 years old.

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Brian Gaff (Sofa 4 years ago

Yes they might all be dead by now form co 2 or breathing soot.

Brian

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Brian Gaff (Sofa 4 years ago

Ah don't make em loike thee used to boy. Brian

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