Stove has been running all day no issues until now. Loaded a half load at 2 PM. Stove temp is up to 500. Cat temp about 1250. Stove keeps backpuffing. Opened the damper to warm the flu and shut it back. Air is halfway where its been all day. 10 min later more backpuffing. Temps about 39 and rainy outside. Have had fires going with much warmer temps and presumably less draft and no issues.
Backpuffing
- Thread starter JohnDaileyNH
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Even with that setting if there is no flame and you have alot of wood off gassing at once that is backpuff territory. With that heavy damp air it may have cut your draft down some as well. You need more draft to pull the wood gasses through before they can collect and ignite. Since the VC's are downdraft stoves the gasses will collect at the top so your draft needs to pull it down and out before it can do that. If you had an updraft stove likely wouldn't be as much of a problem as the gasses have an easier time exiting the stove and/or being burned by the cat or secondary combustion before they can collect in an explosive volume.
So normal to expect this in this kind of weather I assume. Next question, what can I do to help improve the draft? Run the damper open longer to heat the pipe? More air on the primary?
I'd say more air from the primary. At least enough so that some flame is maintained. Also not mentioned but there is such a thing supposedly as too dry wood whereby it would offgass more readily contributing to the backpuff issue. Too dry meaning <13% on a fresh split at room temp. This according to VC not me. My experience is the species and size of splits figures more into it than the mc. But the heart of the issue is the volume of wood gas produced being too much for the draft to pull through and exhaust it prior to its ignition. So basically one of two things, reduce the offgassing or increase the draft to pull more of it out. I think fewer bigger splits as opposed to more smaller splits may help. Maintaining a flame may help with burning off the wood gas before it can collect in volume to be more explosive. Videos I've seen of VC's backpuffing have one thing at least in common and that is the primary air was turned down to the point where there was no flame just a red glow under the wood to try to extend the burn time. In my thoughts and observations the cat does not figure into the backpuffing issue much at all whether it's ignited or not. I don't understand why VC (HHT) is insistent on this downdraft design in their stoves which makes them so complex to run. They can run well with all the stars in line and a good draft. Increasing the draft on my Intrepid recently made a significant positive difference. Increased the draft to 0.06. Enough said at least for now.
Puffing is pretty common with VC stoves especially with the top load.
Yes it's got a lot to do with having the air cut back, but the reason for the air cut back is to keep the cat in check. I've had small flames dancing on the wood and left the stove to smell the smoke from the back puff a short time later. Getting the correct primary air setting is a fine line if the cat is very active, real easy to get to 1600+.
Yes it's got a lot to do with having the air cut back, but the reason for the air cut back is to keep the cat in check. I've had small flames dancing on the wood and left the stove to smell the smoke from the back puff a short time later. Getting the correct primary air setting is a fine line if the cat is very active, real easy to get to 1600+.
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