Should I insulate my liner?

[arnermd]

Hello All,
Looking for some advice to reduce buildup in my liner. I burn 4 cord a year and typically remove 3-5 gal of shiny black crumbs per year after cleaning. Seems excessive to me and wondering if it would be of benefit to insulate the liner, at least the top 2-3 ft or so where the majority of the buildup seems to be. See my installation details below. I typically do not have any draft issues, even with a cold stove on a warm day. I typically measure 0.1 - .18 iwc with a hot flue.

The current liner is 8" uninsulated, corrugated, single wall stainless inside a masonry flue. My VC manual gives the option for 6 or 8" flue but requires
8" to run with the front doors open which I occasionally do.

I have been running this stove for 13 seasons now and the amount of build up has been pretty consistent. I have been getting just under 2 seasons out of my cats and nearly always burn with the cat temps >800, usually over 1000-1200 with full fuel load and occasionally over 1500F when things get out of hand.....

Any suggestions would be appreciated.

 

[EbS-P]

Yes that is excessive. Insulation would help. How long does your wood sit stacked? Do you ever measure the moisture content?

A cat should last 10000 hours. Two years seems short.

The draft seems quite high.

 

[arnermd]

Yes that is excessive. Insulation would help. How long does your wood sit stacked? Do you ever measure the moisture content?

A cat should last 10000 hours. Two years seems short.

The draft seems quite high.

Right... forgot to mention the wood. I let it go at least 2 years under a metal roof. All Ash and Red Oak. I do have a moisture meter, as I recall I am typically around 15% - 20% MC

A Cat should last more than 2 years, I agree.... Have you any experience with the newer Vermont castings flexburn stoves? They eat cats.... very common problem. Probably becuase they lack the ability to control cat temps....

 

[begreen]

Double-walled stove pipe connecting to an insulated liner will help keep the flue gases hotter which will reduce creosote condensation in the flue system.

It would also be helpful to know what the flue temp typically is. Creosote starts condensing below 250ºF. We typically run with about a 400-550º flue temp in a straight up, insulated flue system. After ~7 cords I get about 1-2 quarts of soot and sote, but we are in a milder temperature zone.

 

[arnermd]

Fortunately I have lots of logged data from last year.

The first plot is what I would call a typical burn,

• Flue temp is from a probe in the exhuast gas about 12" above the top of the stove.
• Cat temp is in the gas about 1" downstream of the cat
• Griddle temp is metal temp measured in the center of the griddle twords the back of the stove

This plot is flue temp for the entire burn season. Hard to see details here but you can see typically my flue temps are 300 - 600.


Same plot but for the Cat..... this is why I think my cats don't last. I started the season with a new metal cat from Midwest Hearth. Interesting how the mid winter spikes seem to be worse, could be I was running it harder or maybe it was increase draft from colder outside air temps.

 

[begreen]

Nice data. Yes, those spikes above 1600º are not good for the cat. It would be interesting to see the flue temperature higher up so that it shows pipe temp instead of the stove exhaust temp.

 

[EbS-P]

So in the first graph by 21:00 are you in coaling stage?

 

[EbS-P]

So in the first graph by 21:00 are you in coaling stage?

Edit. I’d try a damper to slow things down a bit. Maybe those mid winter spikes are when it cold and windy

 

[brenndatomu]

A damper, and some insulation would make a big difference