Craftsbury 8392 Catalytic Problems

[wwalker]

Hi all - I'm in my second season with a Hearthstone Craftsbury 8392. I purchased it for its efficiency and the catalytic. Last year was generally good until the end of the season when the catalytic gasket (white rope) slipped out of place every time I tried to close it. This created a loose seal, and caused the fire to extinguish pretty quickly. Dealer told me to keep the cat disengaged for the rest of the season, and I did. Worked ok.

Our dealer, during the annual inspection this summer suggested it wasn't necessary (why install it then?!) and that removing it would eliminate the problem.

He was right. For about 45 days.

We burn daily for about 18 hours, mostly oak/ash/maple/walnut/cherry - all seasoned appropriately.

I am careful to only engage the cat when it's square 'in-the-zone', and began noticing that the fire would struggle when I engaged the cat. I remove excess ash daily and perform a complete clean out near weekly, using a combination of soft brushes and shop-vac to clear any and all ash I can easily access. I gently tap the cat's to knock any additional ash I can.

For the past 3 weeks, when I engage the cat, it kills the fire within 5-20 minutes depending on how hot and packed out it is. I don't want to pay for another service call, but the lack of cat has me running through wood at a wild pace. Not sure if it's normal, but I get the same temp burn for nearly twice as long when the cat is engaged vs not... that is when the cat is working. So not only am I not getting the benefits of the cat, but I'm literally burning through my wood for the season at a faster pace!

Thanks in advance for any recommendations!

 

[stoveliker]

A loose cat seal would not extinguish a fire; engaging the cat increases the impedance of the exhaust gas flow (decreases the suction on the firebox). Having a loose seal there would slightly decrease the impedance.

I think the gasket issue is separate from the performance issue.

To me it sounds like you have marginal airflow through the system, such that when you engage the cat, there's no longer enough flow due to the added impedance of the cat.
This could be because a chimney that's not tall enough, the chimney or cap has an obstruction, an increase in impedance by the cat is too much (clogged cats), or competition for the air in the room/home making it harder to suck in enough into the stove. This could be due to changes in your home such as more exhaust fans (bath, kitchen, radon), better air sealing making it hard for make up air to come in, or more leaks upstairs leading to negative pressures down where the stove is.

Can you describe the flue from stove top to chimney cap?

 

[wetwood4life]

I think your cats are clogged. If the stove used to run smoothly, and now goes out when you close the bypass, it's almost certainly the cats.

My stove (Castleton) is a different design, but had almost the same issue last year. I kept cleaning the front of the cats every week, but the fire kept going out. Over the summer I pulled the cats out of the stove and saw the back was packed like 90% clogged.

We did a deep clean - vacuum it out, then soak them in 25% diluted vinegar for 30 minutes, gently agitate every so often (would recommend an hour or two if you have the patience). The vinegar broke free most of the crusted gunk. Night/day since then. On my stove, the catalysts have a separate "single" use gasket, you might need to buy one to reinstall your cats correctly.

 

[wwalker]

Thanks all - I also assumed clogged cats, but naively hoped that my weekly cleaning was sufficient. I wonder if the annual maintenance this summer came up a little short and I'm dealing with upwards of 8 cords worth of 'gunk'.

@stoveliker - We bought a rancher in '22 and spent '23 rebuilding it into a 2-storey. The attached pic shows the highest point of the roof vs the chimney cap. We're not showing any signs of airflow being the issue and have not experience any negative pressure (yet). I also updated my profile pic to show the stove configuration in house. The exhaust runs up the interior of the house until it pops out the roof.

We're dealing with our first real week of winter in Pennsylvania, so I'm not inclined to pull out that cats until it's a bit warmer. But thank you for the advice @wetwood4life - I'll follow those instructions... and wet wood... I think I know where your 'gunk' came from

 

[stoveliker]

Do you have an outside air connection?