I have a Jotul F500 V2. An hour into my burn a big wind gust put out my fire. This happened twice. I had to open the stove door a crack to get it back. After that it was smooth sailing because the wind either shifted direction or gusts weren't as strong. Is this what a back draft is? We have had issues with wind before and still haven't decided what the best course of action is. We don't now whether to add length to the chimney or get a wind cap. Worried with a wind cap that cleaning will be an issue. We clean from the bottom up. We are not getting on the roof. We are not full time burners and do not do overnight burns that often.
Wind gust put out my fire.
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stoveliker
Minister of Fire
Here are pictures. The first is from the front of the house taken from higher ground. Second is the back of the house taken looking up from downhill. Third is ground level. From some vantage points it looks like it is higher and others I can not tell.
stoveliker
Minister of Fire
I’ll take a stab it being we have a log home too. The house no matter how tightly chinked has a lot of air infiltration. Depending on wind direction it can induce a Postive pressure in the room or a negative pressure.
I’d check historical wind direction on the day it happened and relate it to what side of the house it hit on.
Second walk outside and or get on the roof and look for possible trees or buildings that could shift the angle of the wind towards your stack.
We had some wind inducted back puffing which took a long time to figure out. I intentionally made the stove smoke badly and got up on the roof and studied the smoke pattern and discovered the steep roof pitch was inducing a wild eddy current when the wind blasted out of the south west. Even though we have a tall stack and strong draft simply adding 3 feet solved the issue.
Food for thought.
I’d check historical wind direction on the day it happened and relate it to what side of the house it hit on.
Second walk outside and or get on the roof and look for possible trees or buildings that could shift the angle of the wind towards your stack.
We had some wind inducted back puffing which took a long time to figure out. I intentionally made the stove smoke badly and got up on the roof and studied the smoke pattern and discovered the steep roof pitch was inducing a wild eddy current when the wind blasted out of the south west. Even though we have a tall stack and strong draft simply adding 3 feet solved the issue.
Food for thought.
An hour in to the burn that's not good... Wind cap. I would start with a famco...then vacustack. Famco cleans easy but vacustack requires cleaning...if you don't burn 24/7 probably go evey 3 years. Famco could get lots of wind driven rain and needs to be greased..but it adjusts fast to wind.
If it did it earlier in burn and only twice a season id say live with it...
Have you watched your chimney when it's smoking? Does it leave really long tails or change direction constantly? Where was your air inlet set when stove went out and stt?
Extending the chimney on that setup looks like it would need a lot of support. Might be better to just be under roofline but still within code.
If it did it earlier in burn and only twice a season id say live with it...
Have you watched your chimney when it's smoking? Does it leave really long tails or change direction constantly? Where was your air inlet set when stove went out and stt?
Extending the chimney on that setup looks like it would need a lot of support. Might be better to just be under roofline but still within code.
What direction was the wind relative to the house when it you had a puff back?. My guess is that is what you saw. The wind didnt blow out the fire as much as the change in draft created a sudden increase in air that ignited unburnt fuel. My guess is the wind was coming from the front of the house and out the back downhill. Wind likes smooth surfaces and normally the flow is in parallel layers stacked up from the ground up in the air. Its called laminar flow. Once the velocity increases the air starts to "stick" to the ground and then "unsticks". this will create circular swirls of air near the surface creating turbulent flow. So even though the overall wind is going in one direction, the wind near a stationary surface can be swirling in multiple directions. This effect can be accelerated with sloped roofs and open areas in the surrounding canopy. It looks like the surrounding tree canopy is higher than the house, this creates a area of turbulence around the house. There is no substitute for elevation, the air gets smoother the higher up you go but in some cases, it is not practical. I used to work in a factory in a valley. In order to keep the stack exhaust out of the valley we had to have a 310' stack. Even with that is the conditions were right we could see 100 foot swirls of vapor coming off the stack if the wind were right. The only way to really diagnose the issue is wind tunnel testing but I do not expect many folks would be interested or could afford it.
The backpuff issue is usually made worse when the stove is turned down after a load of wood usually in preparation to going to bed. Modern stoves are machines trying to get the optimal air fuel ratio at the right temps. The air flow is related to flue gas flow, temperature and differential pressure from the air intake to the stack outlet. Turbulent flow messes with the differential. The wood off gassing responds slowly while air flow responds quickly. The net result is with a changing pressure differential on the stack, the wood can be offgassing with less air than it needs and it goes to a lean fuel ratio, rapidly increase air flow and that stack full of hot lean partially combusted gas can start burning much more rapidly causing it to expand rapidly, in some cases that can blow out the fire but normally its just a pressure pulse. Older cookstoves frequently had top cooking plates that just stay in the stove by gravity in a tapered hole, if they had a backpuff the plates would lift. My old VC Defiant had that issue and are known to backpuff, they also had a thin metal air intake flap. On windy night I could hear the backflap rattling and learned that I had to be real careful to add wood slowly and avoid trying to crank down the air ro the result was a backpuff that could lift the cooking plate. That is one of the reason why VC owners frequently had a cast iron pot full of water on top of the cook plate to weigh it down
.
The problem as you note is if you put a resistance in the stack like a cap that can cause plugging especially if your wood is marginally dry (dry wood rarely makes creosote and creosote condensing on the screen is what plugs it). Clean stoves running dry wood rarely have that issue unless the stack draft is marginal or the stack is uninsulated. Some folks swear by having a key damper down near the stove as a partial fix, once the stove is let and going, crank down on the damper a bit, that can reduce impacts from changes in outlet draft. The problem is most of the time you do not need it so its easy to forget to crank back on the damper. Flue geometry also can factor in, if a stove dumps into large flue, the velocity in the stack is lower than optimal and it can make it more prone to turbulence on the stack outlet. Some folks go larger than needed on flue diameters and that can screw up stack outlet velocity. Gases exiting a stack at high velocity tend to punch through local turbulence. Old Jotuls used to come with odd usually small diameter flue outlets and folks would adapt them to larger diameters and they could act up. Swap them to the right smaller diameter and they would run better.
The backpuff issue is usually made worse when the stove is turned down after a load of wood usually in preparation to going to bed. Modern stoves are machines trying to get the optimal air fuel ratio at the right temps. The air flow is related to flue gas flow, temperature and differential pressure from the air intake to the stack outlet. Turbulent flow messes with the differential. The wood off gassing responds slowly while air flow responds quickly. The net result is with a changing pressure differential on the stack, the wood can be offgassing with less air than it needs and it goes to a lean fuel ratio, rapidly increase air flow and that stack full of hot lean partially combusted gas can start burning much more rapidly causing it to expand rapidly, in some cases that can blow out the fire but normally its just a pressure pulse. Older cookstoves frequently had top cooking plates that just stay in the stove by gravity in a tapered hole, if they had a backpuff the plates would lift. My old VC Defiant had that issue and are known to backpuff, they also had a thin metal air intake flap. On windy night I could hear the backflap rattling and learned that I had to be real careful to add wood slowly and avoid trying to crank down the air ro the result was a backpuff that could lift the cooking plate. That is one of the reason why VC owners frequently had a cast iron pot full of water on top of the cook plate to weigh it down
. The problem as you note is if you put a resistance in the stack like a cap that can cause plugging especially if your wood is marginally dry (dry wood rarely makes creosote and creosote condensing on the screen is what plugs it). Clean stoves running dry wood rarely have that issue unless the stack draft is marginal or the stack is uninsulated. Some folks swear by having a key damper down near the stove as a partial fix, once the stove is let and going, crank down on the damper a bit, that can reduce impacts from changes in outlet draft. The problem is most of the time you do not need it so its easy to forget to crank back on the damper. Flue geometry also can factor in, if a stove dumps into large flue, the velocity in the stack is lower than optimal and it can make it more prone to turbulence on the stack outlet. Some folks go larger than needed on flue diameters and that can screw up stack outlet velocity. Gases exiting a stack at high velocity tend to punch through local turbulence. Old Jotuls used to come with odd usually small diameter flue outlets and folks would adapt them to larger diameters and they could act up. Swap them to the right smaller diameter and they would run better.
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