Gas boiler flames affected by wind

[405 TD Estate]

When my gas boiler is on and it's quite windy outside the flames are affected by the wind quite a bit - as if it's windy where the flames are yet as its an old type the inlet air comes from the house and the outlet is a stack running from the ground floor to the roof guttering line and has no faults / holes etc I can see and looks in good condition and has a berathing type cap on the top. What's going on?

I have a CO monitor and the level increases (still within safe limits) when this occurrs so obviously it's not burning properly.....

[John Rumm]

It sounds like the wind is affecting the amount of draw the chimney stack is providing and hence altering the air rate at the burner.

[Andrew Gabriel]

It could be forcing fumes back down the chimney, which then get used as the burner air intake, and with reduction of oxygen present, cause CO increase. Has anything been built up around the height of the chimney outside since the chimney was built which might be interfering with the airflow up there? What sort of ait intake is there into the room from outside?

Boiler shouldn't be producing much CO in the first place if it's been properly serviced. Has it been regularly serviced? That's really important with an open flued boiler. What level of CO are you observing?

[405 TD Estate]

There is a vent block into the kitchen all be it behind cupboards but they would not stop the flow of air so I would be happy air can be drawn into the kitchen - also the kitchen is open to the rest of the house so it could draw air from there. What I find strange is the chimney - a 6" diameter (roughly) pipe is very very long - upto the roof guttering and yet the wind which can only blow across the top of it (and it has a rain cap type thing on as well) can affect the flame probably 15 feet below!

I've just had a thought - perhaps the rest of the house is put under

+ve pressure with the wind (wind blowing on one side of the house or something) and there is a -ve pressure as the wind blows across the top of the exhaust chimney so too much air passes through the boiler? Sound plausable?

[405 TD Estate]

upto 10ppm for short times. (when boiler is on)

[John Rumm]

Just blowing across the top of a pipe will cause a pressure drop that will tend to suck a fluid up the pipe.

[meow2222]

re wind blowing affecting the flame, this is bound to happen with your type of flue. As long as its not going out, is burning ok and is not polluting the indoor air, no problem. Someone else will be able to tell more re the CO levels.

Yes, though IRL the wind will travel in various directions, often turbulent, so it will blow both in and out of the pipe to some degree.

NT