Air leak or overdraft?

I have a Buck Model 81 Non-Cat insert which I bought used. It is in the basement of my house and vents through a 5.5" flex liner which is 31' tall. The insert tends to burn hot and fast; even when fully damped down. It flames up a lot and I don't feel like I can control the burn the way I want to. The door fits tight and the seal was recently replaced on the door.

I use this insert sparingly because I don't quite trust it. When I do use it, I don't put much wood in at a time. A few splits and that it is. It has a large firebox, so it can take a lot more. I've also never been able to achieve a nice secondary burn like I can with the Hampton insert.

I did come across this website which suggests that large non-cat stoves with tall flues tend to be difficult to control and consume wood quickly: chimneysweeponline.com/hoxdraft.htm

I have also noticed that the left side of the stove seems to flame up more than the right side. The air intake appears to be on the left side on the bottom the insert, but the air appears to enter in the center of the burn box near the door. This insert has an ash pan which I don't use. The door for the ash pan is also on the left side, so I guess it is possible that air could be leaking in from the ash pan. I visually inspected the seal for the ash pan, and it looks ok.

So my question is do I have air leakage issues, or an overdraft issue? I'm considering having the Buck dealer from the area to come out and give me an assessment. Otherwise, I'm considering selling the Buck and going to a catalytic Blazeking insert. I like the idea of the extended burn times of a cat insert, but it would also cost me a lot of money for another insert.

I have attempted to block off the intake a bit more. I took some heavy duty foil and slipped it underneath the damper plate to get a tighter fit over the air intake. It may have helped a little bit, but definitely did not completely solve the problem.

I'll probably go down the path of having the Buck dealer come out to suggest some remedies. If nothing works though, could I swap this out with a Cat stove and resolve the problem, or would a Cat stove still have the same issues with a strong draft?

pen said:

Have you seen this article? http://www.gulland.ca/florida_bungalow_syndrome.htm

That 5.5 at 31 feet is like a hoover drawing on that stove.

I'm not one to do a modification for the fun of it. But I think this may be a case of where it would be advised.

That must be a monster draft on the stove.

pen

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Pen, this is a really good article which describes the issue in much greater depth than the link I posted. Thanks for providing that.

Ok, I just had a big 'Ah ha!' moment. There are two air intake holes on the bottom of the insert, one of the left and one on the right. There is a slide that moves left to right that pushes a small steel plate over the air intakes. The plate that covers the right intake is missing.

I covered the intake with a piece of foil and voila, a it was a completely different insert. Interestingly, it seems that the intake on the right feeds the left hand side of the stove, and vice versa. This explains why the fire was always ragging on the left side of the stove where the ash pan is. With the foil over top of the intake, my insert no longer looks like the fires of Hates.

All I can figure is that the screws must have been loose on the plate and it fell off when it was being moved. I can see where the holes were already drilled into the slide where the plate was attached. New plate ordered from Buck Stoves today.

PLAYS WITH FIRE said:

with the 91 I'd furnace cement it closed and put a piece of fire brick over it.

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It wasn't the ash pan. One of the air inlet covers was missing.

I found the missing air inlet block laying all the way in the back of the bottom of the insert. I was able to retrieve it with a magnet, and found a couple screws laying around that were just the right size to reattach it. The insert is a completely different animal now. Perfect timing too since it is supposed to go down to -6 overnight.