Unusual behaviour

alleycat`

I seem to have seen this on here before and can't recall the outcome but i had an odd experience with the stove today.

I think it is down to the wind and direction but i thought i'd run it past everyone else to see what they think.

Lit the stove as usual, bit of kindling, firelighters away we go.
Stove is up to about 200F and i add a couple more pieces of wood to get it off as normal.

It climbs to about 220 or so, suddenly the stove goes out, flames just die, and a massive puff of smoke comes back in via the top vent.

About 15 seconds later the stove "re-lights" and off it goes again, it the does this about 4 or 5 times over the next 15 minutes.
Each time it appears to coincide with the wind actually "stopping", then actively "roaring past the window".

Once the stove gets up and over 350 the problem goes away and hasn't repeated.

I'm wondering if it was a function of the chimney working in reverse in some way (possibly as it was still cold'ish).

I know i'm due a sweep in the new year but it doesn't seem to be a function of "blockage" but more the air getting drawn down the chimney in some way.

My chimney isn't lined, it is one of those "lego" type ones similar to pumice but i'm almost certain it is concrete based and it isn't very old.

I'm guessing it is to do with cold chimney / warmer house but it is very odd and thought it worth an ask.

SEE

Very strange, has the chimney got a cap to prevent birds getting down?

dacouch

Probably momentary lack of oxygen

alleycat`

SEE wrote: »

Very strange, has the chimney got a cap to prevent birds getting down?

Yes it does have a cowl, made by colt, it isn't an anti-down draft variant.
I'm considering i might need to change it.

alleycat`

dacouch wrote: »

Probably momentary lack of oxygen

If it was just that i'd expect the fire to go out but i don't understand why the smoke would get forced out of the top air vent.
The behaviour is almost like the air is getting forced into the room down the chimney.

The stove was fine last night, wind was a slightly different direction and less gusty.

Swipe

I wouldn't be overly concerned unless it was happening on a frequent basis. Sounds like a one off down draft to me when the wind happened to blow in a certain direction.

muckybutt

We sometimes get it alleycat, I dont have a downdraught cowl on as it only happens a handfull of times a year when the wind is in one direction, chimneys can be funny things at high levels especially if there are high trees or buildings near you, these all afftect the air flow and can create turbulance at roof top height which causes down draught.

It could also be caused by any internal vents you have in the house such as bathroom or kitchen extractors, these all need to have backdraught shutters on them, but you can also get backdraught in other ways as well.

If it becomes more of a problem I would suggest getting a backdraught cowl on, i'm also hoping you have a carbon monoxide detector in the same room as the stove.... just in case.

alleycat`

We don't have trees but we do have an odd arrangement of houses that can funnel the wind in one particular direction.

I'm looking at some of the extractor covers and the air brick with regards to how the covers work for them.
If it becomes an issue with the direction of the wind i'll have to take some proactive action with them.

I have 2 CO alarms as it happens.
One in the room with the stove and one upstairs near the bedrooms.
I'm always paranoid one will let me down

G_M

It's downdraft.

Depending on location/alignment of chimney, and wind direction, you can get downdrafts.

I get this all the time (particularly bad - have tried several specialist cowls without success!). In my case I learnt (LOTS of googling) that because my house is built on the side of a hill, with the chimney extending well above roof height, when the wind blows over the top of the hill (in my case from the north) it then swoops downward towards the roof line... and down the chimney.

Once you have sufficiently high temperature, the effect is reduced/cancelled by the effect of heat rising. So the hot air going up cancels the cold wind coming down (or not, in my case )

Try anti down draught cowls.....