Stack Temperature

I have a mid-80's Coal/Wood combo Stove. Someone else has posted about having the same model (slips my mind). The question is after reading tons of posts about 135, 250, 375 degree "F" stack temperatures. What would be "typical" for a temperature to see on a stack for a vintage stove like this? There is no high tech here, I crack the below grate air to allow the fire to burn relying on the natural draft of a 35 foot chimney to draw. My pipe is too hot to touch. If I was to open the air wide open, 3/4 open, half open or even 1/4 open the heat will drive you out of the room. I want to improve my efficiency and reduce my consumption which is 2 five gallon pails a per 24 hours. I am thinking about putting a shell around the stove to put a blower system in it so I can keep the fire turned down and get more heat out of it.
I am borrowing a temp gun from work this work and will know more by next post.
drujinin

The temperatures can vary widely, even with the same model unit. Sounds like you need a barometric damper if you don't have one, a 35" chimney can pull a serious draft. A handfired unit should stop drafting at about .060, anymore and you are sucking up heat and coal.

0.06"? Are you sure you didn't mean 0.6"
I would have to walk over to the LAB and look at an inclined water manometer but I didn't think they would read down that low.
Anyways I choked it down some more last night to see if the fire would go out and it doesn't so I am running cool enough to touch the pipe for a second or two. I am going to drill some probe holes in it just to get some readings on temp and suction.
Its warm outside today which isn't agreeing with the weather forecast which makes it hard to get good stack draw values.
The only reason I have been hesitant to put a barometric damper on it is because I can't deal with the fact that would suck warm air out of the house. Of course when I am burning wood it should help with that also.
I do suppose the reasoning is suck air through the fire and use more fuel in return for a small degree of warmth or suck out of the warm room an equivalent amount of air in return for a fuel savings.
Is this a correct assumption??
drujinin

drujinin wrote:0.06"? Are you sure you didn't mean 0.6"

The only reason I have been hesitant to put a barometric damper on it is because I can't deal with the fact that would suck warm air out of the house.

Actually, the reading is -.06 as the draft you read is lower than room pressure.

You are saving the 70* air from your room and sacrificing several hundred * air to the chimney and outdoors. GET A BARO.

OK!
I need to upgrade the pipe quality and do an inside chimney inspection anyways.
drujinin

Where is everybody taking their readings? Right now I have a magnetic Rutland gauge on my Harman Mark II's stack about 12" above the stove, which is 1/2 way to the barometric damper.
It's 32 outside, and my 6" stack goes up maybe 6' before turning then 2' into a, 8X8" brick chimney that is probably about 30' tall.
The stove is burning good, approx. 3/4 full of pea, with 2-3" dancing blue flames over 80% orange coals. Circualting blower is off.

Moving the magnetic guage around, the temps are:
Side of stove near the top - 490
Stack 12" above stove - 280
Stack 12" above barometric damper - 155

The only ballpark numbers I could find online are from Hearth.com's Q&A where they say a coal stove at 450-475 degrees should have a stack temp of 225-250, but where do they take those readings?

I think I'm probably running a little on the hot side, so I'm going to cut the air back 1/4 turn for now.

Any thoughts or suggestions?

Thanks,
Steve

Mastiffman wrote:Where is everybody taking their readings? Right now I have a magnetic Rutland gauge on my Harman Mark II's stack about 12" above the stove, which is 1/2 way to the barometric damper.
It's 32 outside, and my 6" stack goes up maybe 6' before turning then 2' into a, 8X8" brick chimney that is probably about 30' tall.
The stove is burning good, approx. 3/4 full of pea, with 2-3" dancing blue flames over 80% orange coals. Circualting blower is off.

Moving the magnetic guage around, the temps are:
Side of stove near the top - 490
Stack 12" above stove - 280
Stack 12" above barometric damper - 155

The only ballpark numbers I could find online are from Hearth.com's Q&A where they say a coal stove at 450-475 degrees should have a stack temp of 225-250, but where do they take those readings?

I think I'm probably running a little on the hot side, so I'm going to cut the air back 1/4 turn for now.

Any thoughts or suggestions?

Thanks,
Steve

My Harman is currently running at 225 degrees stack temp. The gauge is on the vertical pipe between the outlet and the tee where the baro is. My draft is running at -.06 WC, the chimney is about 30' tall, masonry, on the outside of the house. Draft vent is open 2 turns, stove 3/4 full of pea coal. At 1 turn it runs about 150 degrees. Before I installed the baro the pipe temps were much higher, the paint on pipes would start to smoke and I would get a combustion odor, I think the pipe connections expanded so much that the seams opened up a little.

29 degrees outside now.

It's recommended to keep the stack temperature at or above 350 degrees to prevent condensation in an uninsulated chimney. My wood/coal boiler using dried wood varies widely in temperature. Even with a hot fire, my stack temperature is around 150 degrees once it settles down. I had a terrible time with creosote last year before I tore out the clay liner and installed a stainless liner wrapped with ceramic fiber and foil.

That's the beauty of coal, though! No condensation issues to worry about, and hence - no creosote! We only need enough heat in the exhaust to develop the required draft (or in my case, I have a direct vent stove - no heat needed at all). But yeah, with wood, on a cool fire and long chimney, you can get GALLONS of creosote liquid running out everywhere. Been there, done that. What a smelly mess.

So, if coal causes no condensation, is a 350 stack temp. too high??

A stack temp of 350* is pretty hot for a coal stove. Around 200-250* is wasting a lot less heat up the flue. If you need to have your fire burning so hot that the flue is above 3-350* , then maybe you should look into trying to get more heat off the stove body with a fan or a better fan. A stack temp of 3-350* is going to have the stove at 500*-600*+ . If some of the stove heat is washed off with a fan, the stack temp will drop, the room temp will rise. and that is what we are looking for, a warm room.

Greg L

Right now my stack temps shows 115 with stove top at 250. Our big pot of chilly sure is enjoying it going into the 5th hour of cooking.

When I say 350 degrees stack temp, I mean at the breech of the unit.

I'm sorry for asking but what or where is the breach of the unit?

By the way there is an add on the website or in the wisconsin farmer paper for bagged nut coal in a 920 area code.

The breach is where the heat exits the stove or where the flue pipes begin.