Getting Catalytic Burn

[CTstove]

Hi Everyone,

Could use input on what I might be doing wrong with my Vermont Castings Intrepid II. I'm still new to burning with this stove that came with a house I bought. I did read the manual and FAQ on this site.

I got a fire going with the damper open and brought it up to 450 degrees after 1.5 hours based on the stovetop thermometer. When the damper was closed smoke started coming out the doors so it failed to draw in the catalytic mode. I opened the damper and let it go another 30 min to get temp up to 550, but still no draw when switched to catalytic mode.

I've got good seasoned hardwood and recently cleaned the refractory chamber and catalyst. Any suggestions? Temps here have been in the 30's and I guess the draw will be better when it's even colder, but I really want to run the stove.

Thanks for any ideas.
Chris

 

[stovelark]

Hi Chris- Sounds like you are doing the right stuff. What size is the chimney flue? Could be the chimney flue is larger than optimal and is staying cold not letting it draw. Also, is the cat element in good condition? Is it blocked ? Couple of things to think about. Might be time for a new cat,

 

[CTstove]

Hi Chris- Sounds like you are doing the right stuff. What size is the chimney flue? Could be the chimney flue is larger than optimal and is staying cold not letting it draw. Also, is the cat element in good condition? Is it blocked ? Couple of things to think about. Might be time for a new cat,

The catalyst is structurally intact. No cracks or crumbling and I blew it out. Would it be better to measure the temp on the stovepipe?

 

[stovelark]

Hi Chris If you are hitting those temps on the stovetop, that should be hot enough to support catalytic operation. Do u know what size the chimney is? I'm thinking that might be the issue. Its cold enough now that draft should be good. in bypass, can you run the stove in a normal temp state? I mean, once it hits 400 to 500, can you adjust the intake air control to run the stove? I know the stove would be more effective in cat mode, but if u can run it in bypass, you can still run the stove, it just will not be as efficient. i'm still wondering if the cat is no longer active, even if it looks ok....

 

[RandyBoBandy]

I typically don't pay attention to my stove top before engaging the bypass. I wait until my stack is above 400. If everything is clean in the stove like you say it is then I would have to poor draw. What are your chimney specs?

 

[CTstove]

Thanks stovelark and Randy for the replies. Being fairly new to the game, I don't know all the specs of the chimney. It has a clay liner, and about half its length runs through an internal wall in the house.

I'll first try putting the magnetic thermometer on the stack and wait till that gets above 400 before closing the bypass damper and switching to catalytic mode. It sounds like there's just not enough draw and maybe that will help. Although the stove runs perfectly well with the bypass open, I don't see much change when adjusting the air intake. The next step would be replacing the catalyst I suppose (or just run in with the bypass damper open).
Chris

 

[ddddddden]

I typically don't pay attention to my stove top before engaging the bypass. I wait until my stack is above 400. If everything is clean in the stove like you say it is then I would have to poor draw. What are your chimney specs?

+1

Even if your catalyst were not active, as long as it's not physically clogged, I think the exhaust should still flow out of the stove. Something else in the stove could be obstructing flow, but you said you have cleaned the refractory chamber, and I'm not familiar enough with VC to have an opinion on anything else inside the stove, so. . .

tell us all about your chimney.

Even a perfectly clean catalyst presents a lot more resistance to exhaust flow than an open bypass door does. If something about your chimney is not right, it may have enough draft to pull through the open bypass, but not enough for the catalyst + refractory chamber.

 

[ddddddden]

...I don't know all the specs of the chimney. It has a clay liner, and about half its length runs through an internal wall in the house...

Ah, the ol' masonry chimney. You're probably going to want to run a 6" liner pipe through there. Most masonry chimneys are sized for a fireplace. Way too big to draw properly with a stove.

https://chimneysweeponline.com/hoosst.htm

https://www.hearth.com/talk/threads/reline-a-masonry-chimney.147725/

 

[RandyBoBandy]

Ah, the ol' masonry chimney. You're probably going to want to run a 6" liner pipe through there. Most masonry chimneys are sized for a fireplace. Way too big to draw properly with a stove.

https://chimneysweeponline.com/hoosst.htm

https://www.hearth.com/talk/threads/reline-a-masonry-chimney.147725/

And insulate the liner if possible

 

[RandyBoBandy]

If you haven't been able to get the cat purrin I bet the original home owner couldn't either. Which leads me to believe that cat is absolutely fine.

 

[webby3650]

It’s been a while since I tore one of these apart.. you were able access all parts of the refractory box? Not just directly around the catalyst?

 

[CTstove]

First, thank you all for your input. I'm looking forward to becoming a wood stove burner. From your replies, it sounds like the chimney specs are the culprit and the original owners faced the same issue. I do believe, since it is an independent chimney for only the stove, that it must have been designed for that, but it probably wasn't optimized for a catalytic stove due to either the chimney dimensions and/or liner. For now I'll run it as a regular stove with the bypass damper open. At some point I'll get it professionally evaluated. I was hoping to use it so save money and not sink money into it, though.
Chris

 

[CTstove]

It’s been a while since I tore one of these apart.. you were able access all parts of the refractory box? Not just directly around the catalyst?

Right, I opened a chamber at the back of the stove to access the refractory chamber and vacuumed out the two compartments on either side of the cat that were full of ash, as the manual instructed. There is no catalyst temp probe, which I guess from reading is ideal, to know when it lights off. All I have is a magnetic thermometer on the top.

 

[RandyBoBandy]

If your goals are to heat your home I would say get the chimney inspected and lined as soon as possible. You will be happy you did when it's January or February and you are enjoying extended burn times with a properly running cat. I also suggest a cat probe. AT100 from Auber instruments is what most VC burners use.

 

[ddddddden]

...I do believe, since it is an independent chimney for only the stove, that it must have been designed for that, but it probably wasn't optimized for a catalytic stove due to either the chimney dimensions and/or liner...

You're saying that there was never a fireplace associated with this chimney? Even if it was built for a stove, older stoves tended be larger and had an unrestricted exhaust path, like your stove runs with the bypass open. I wouldn't be surprised if your flue is at least 8 x 8" = 64 sq in, more than double the 28 sq in area of the 6" flue on most modern stoves. This extra area allows the exhaust to expand, cool off, and slow down. It might work when conditions are ideal, clear & cold out, but this is not a good recipe for consistent performance, and the variation in performance will drive you nuts, if you're trying to use the stove as your main source of heat.

For now I'll run it as a regular stove with the bypass damper open...

You may want to try running it with the catalyst removed instead. Burning hot with the heat passing through the bypass may warp the bypass door/frame.

 

[webby3650]

First, thank you all for your input. I'm looking forward to becoming a wood stove burner. From your replies, it sounds like the chimney specs are the culprit and the original owners faced the same issue. I do believe, since it is an independent chimney for only the stove, that it must have been designed for that, but it probably wasn't optimized for a catalytic stove due to either the chimney dimensions and/or liner. For now I'll run it as a regular stove with the bypass damper open. At some point I'll get it professionally evaluated. I was hoping to use it so save money and not sink money into it, though.
Chris

I’ve not known the older VCs to be all that temperamental. Unless that flue is really big I’d be surprised if it was the culprit here. I could see the cat crashing after a while, but not smoking out the stove if the bypass is closed. I really think if the draft was that bad, it would struggle at other times as well. Especially with cold starts.

 

[ddddddden]

Performance on cold start would be good info.
If the cat and refractory chamber are unobstructed, and draft is sufficient, what does that leave? Bad gasket?

 

[stovelark]

I tend to agree with webby- if the stove will run in bypass suitably, the chimney sounds like its drafting... what is the setup like connecting to the chimney? Does it really take 1.5 hrs to reach 400 degrees? I know the intrepid is a smaller stove and some stove flues were 7x11 and 8x12 as well as 8x8, which would certainly work against it as well. I know a 6 inch liner would enhance draft in any condition. Is the chimney connector pipe tightly sealed? Maybe a clean out door from the flue not closed well? Maybe a chimney cap partially clogged with creosote? Just pondering all possibilities.

 

[CTstove]

I tend to agree with webby- if the stove will run in bypass suitably, the chimney sounds like its drafting... what is the setup like connecting to the chimney? Does it really take 1.5 hrs to reach 400 degrees? I know the intrepid is a smaller stove and some stove flues were 7x11 and 8x12 as well as 8x8, which would certainly work against it as well. I know a 6 inch liner would enhance draft in any condition. Is the chimney connector pipe tightly sealed? Maybe a clean out door from the flue not closed well? Maybe a chimney cap partially clogged with creosote? Just pondering all possibilities.

Maybe this is a clue. If it is very cold out, the stove starts up like a dream and I can get a good hot fire quickly. But as it gets into the 30s, it becomes a struggle to get it going and really takes 1-2 hours to settle in. It does draw, but the fire is sluggish and slow to build. Once it dips into the 20s, then it cranks.
Chris

 

[CTstove]

I tend to agree with webby- if the stove will run in bypass suitably, the chimney sounds like its drafting... what is the setup like connecting to the chimney? Does it really take 1.5 hrs to reach 400 degrees? I know the intrepid is a smaller stove and some stove flues were 7x11 and 8x12 as well as 8x8, which would certainly work against it as well. I know a 6 inch liner would enhance draft in any condition. Is the chimney connector pipe tightly sealed? Maybe a clean out door from the flue not closed well? Maybe a chimney cap partially clogged with creosote? Just pondering all possibilities.

There's no clean out door or cap on this chimney. As I mentioned, we bought this house a couple years ago and I'm only now getting around to burning the stove so I recently took off the stack and pulled connector pipe out of the chimney to inspect them. There was some sealant around the connector pipe that fell off in the process. When I reinserted it back into the flue, it appeared to fit snugly.
Chris

 

[ddddddden]

Sounds like you have inspected the indoor pipe. . .I'm sticking with oversized chimney. If you can get on the roof, this is easily measured. You could also get some idea by sticking a ruler into the hole where your connector pipe enters the chimney. Yeah, there might be a leak somewhere in the old masonry, but your best solution would still be to drop a liner pipe down the chimney. Liner kits start @ $300. If the stove still does not perform well, and you decide to get a new $600 non-cat stove rather than rebuild the VC, which can be $$, your chimney will be ready.

 

[RandyBoBandy]

Have we touched on moisture content of your firewood? It really needs to be below 20%