Buck 91 with smoke smell

[MatlockJ]

So, just bought a used Buck Model 91 (about 5-6 years old, but in good condition), installed it in my masonry fireplace and noticed a smoke smell whenever the blower kicked in. I know I've made a few mistakes with installation along the way, which I'm trying to rectify. Here's the full history:

First, installed it with a steel chimney flue liner (6", because this would fit inside of the 8" square terra cotta flue tiles). Initially, I thought the smell was from a leak somewhere, but I haven't been able to find a crack (although I can't exactly see the top air cavity around the catalytic converter), then I had a revelation the other night when looking around with a bright light looking for smoke: I saw a fine line of smoke being drawn out of the air inlet (just below the front door and just in front of the blower intake). I closed the air inlet and pressed to seal it, and smoke smell decreased greatly. In retrospect, I did get smoke billowing out the door whenever I would open it, even after opening the shotgun for a few minutes.

So, now I'm thinking the smell is at least partly due to poor draft, especially since I was decreasing the 8" flue to 6". I'm thinking of removing it and installing 8" flue to the base of the terra cotta tiles and removing the liner inside of the terra cotta, as they appear to be in good condition and would be about the right size. I had a much smaller / cheaper Century Heating insert I bought from Ace in the space previously, and never had any smoke smell (replaced with the Buck in hopes of heating the whole house).

Am I completely off in thinking this way? Anybody else with a late-90s / early-2000s Model 91 have similar problems, this seems to be a design prone to backdrafting whenever the blower is on. Thanks in advance for your advice, you all seem to be a neverending source of fireplace knowledge.

 

[pgmr]

The blower shouldn't be causing the problem, though it might make you notice it by distributing the smoke. Does the stove backdraft when the bypass is open? If so, then you have a poor draft. How tall is your chimney?

When did you do this install and test burns? It really hasn't been that cold yet in the Midwest, so you're not getting the kind of draft you will when it's really cold.

 

[Chargerman]

I am trying to figure out why having the blower on would effect draft. They are basically a metal box built inside another box and the blower just pulls air in and out between the two.
Are you opening the door when the Cat is engaged? You should open the damper before the door with a catalytic stove. I would guess the 6" flue is not helping matters at all. How tall is the chimney?

Also, are all your door and window gaskets sealing? I would guess the blower is making whatever leak you have more noticeable but I don't quite get the draft reduction.

 

[davidmc]

Hi MatlockJ. I would think it was solely a draft issue. These large stoves require an 8" flue to properly draft. I am planning to start my curing fires this weekend. All the large Cat stoves need the 8" flue. For 8 yrs. prior to this Buck I ran 2 VC Dutchwest stoves. The large and XLarge both required the 8". I have a link for the buck manual if you have not read it this will help.

http://www.buckstove.com/stovemanuals.html

 

[MatlockJ]

Thanks for your replies.

pgmr: The stove does backdraft when the bypass is open, although it is (predictably) a lot better when hot. The chimney is 15' tall to the inch. Installed over the past two weekends...granted hasn't been cold yet but with such a significant smoke smell, I'm not sure that the cold weather will solve the problem...

Chargerman: I think the blower isn't really affecting draft, but perhaps poor draft + the fact that the blower intake is literally 3" away from the damper opening is causing smoke to be pulled backwards through damper and into the blower intake. I noticed backdraft even when the cat is not engaged. The door and window gaskets are sealing well (switched them all out when I bought the stove), and the smoke smell seems to be coming directly out of the blower vents on top of the insert; ie there is no smoke smell directly around the door or the side windows.

davidmc: Yeah, I agree with you, but still somewhat concerned that there might be a leak somewhere since I haven't owned the stove since new. I read the manual & recommendation for 8" flue, was hoping to get away with the 6" from my previous stove.

Do you all see any problem in me running a 8" steel liner to the base of the terra cotta flue tiles & sealing the liner directly to the tiles? The tiles aren't big enough to permit an 8" liner all the way to the top. Also, do you all have any clever ideas for seeing if this is, in fact, related to a crack somewhere that I can't see (or do I need to just get the larger flue in place first before tracking down anything else)?

Thanks much for your help everyone.