Stove Top vs Pipe Temps in Tall Chimneys

[wkpoor]

Oldspark thought this topic worthy to revisit so I am posting it.

I would like to here from people with chimneys 35' or greater. Since I always have had stove pipe temps significally lower than stove top, even on reload, and have never seen it another way I naturally assume that to be normal. After reading on here it seems pipe temps at or above stove top are common and more the norm. I have operated 2 pre EPA stoves and 2 post EPA stoves in same location with same results. An example is if my stove top is 600 I will have a 200 pipe. I have on occasion seen 500 pipe but only after I force it there with cardboard or a bunch or small splits with damper and draft wide open. A typical day for me is damper and daft full closed. Even today with 57 degree OAT.
The old Nashua that I sold to buddy is on another very tall chimney and he is reporting exact same results.

 

[oldspark]

A lot of interest in this I guess, was hoping for some one with a similar setup for chimney could tell up what their flue temps are.

 

[wkpoor]

Got home after work last night (or early this morning actually), opened both damper and primary, reloaded the stove and left both open to see. Hottest the pipe got was 300 with a roaring stove full of flames and then it started to settle back as temps went to 600. That was plenty enough heat for these warm temps so damper and primary were shut down leaving me with nice secondary flames. Pipe temps quickly cooled to 200. If I had left the damper open temps would have continued to climb but that 2-1 delta would have remained.Thats pretty a typical scenario.

 

[pen]

I think some of the confusion here comes from folks having a soapstone stove.

Soapstone takes a while to heat up compared to steel. When the cat isn't engaged a lot of heat is going up the flue and since the soapstone is slow to react, it only makes sense that pipe readings would be higher than the stove itself.

In general, even on my steel stove w/out a cat there is a short time at the beginning of a load where the stove pipe is hotter than the stove itself. About the time they even out is when I start closing the air down.

pen

 

[wkpoor]

That may be a small part of it but if you read carefully I never see that short time you spoke of. In fact never gets even half of stove temp. Then there is the sustained temps after everything up and running with the primary backed off. Do you see those at about 3-1?

 

[pen]

Use many different thermometers or an IR thermometer? Wondering if the difference is in how fast different thermometers react. The newest condar surface thermometer I picked up for the stove pipe is extremely fast compared to the rutlands I'd used in the past. The difference is remarkable. Won't be owning another rutland I can tell you.

Usually my surface temps of the pipe (about 16 inches up) are 1/2 to 2/3 of the temperature of my stove top. for example, if the stove top is 700 it's normal to have a 400-475 degree stove pipe.

pen

 

[wkpoor]

Use many different thermometers or an IR thermometer? Wondering if the difference is in how fast different thermometers react. The newest condar surface thermometer I picked up for the stove pipe is extremely fast compared to the rutlands I'd used in the past. The difference is remarkable. Won't be owning another rutland I can tell you.

Usually my surface temps of the pipe (about 16 inches up) are 1/2 to 2/3 of the temperature of my stove top. for example, if the stove top is 700 it's normal to have a 400-475 degree stove pipe.

pen

I have 4 rutlands and they all agree very close to each other and have all been compared to 2 difference IRs. Reaction time still doesn't explain cruising temps which your pipe numbers are significantly higher than mine. I'm measuring pipe temp about same distance as you above stove.

 

[Huntindog1]

I dont have a 35 foot flue but I have a pretty tall one at over 25. My stove likes to cruise at 400 stove pipe (15" up) and stove top temp at 600 to 700 with good dry wood like a load of oak. If I dont load good wood like that there is a noticeable differnce in heat output. I can get the stove pipe to 500-600 with smaller stuff or loading on a bigger and hotter bed of coals. But I have to work at it as the stove likes to cruise with a stove pipe temp of 400 like its a tuned machine or something. One thing I like to see is a good temp difference between the stove and pipe. Tells me all my heat isnt going up the chimney.

 

[Backwoods Savage]

I think some of the confusion here comes from folks having a soapstone stove.

Soapstone takes a while to heat up compared to steel. When the cat isn't engaged a lot of heat is going up the flue and since the soapstone is slow to react, it only makes sense that pipe readings would be higher than the stove itself.

In general, even on my steel stove w/out a cat there is a short time at the beginning of a load where the stove pipe is hotter than the stove itself. About the time they even out is when I start closing the air down.

pen

Sorry Pen, I think this is wrong. It just stands to reason, even with a steel stove. If that stove is cold and you start a fire, that flue will get hotter than the stove. No, it will not stay that way nor does it stay that way in a soapstone or a cast. The point, and I think it is being misunderstood, is that when you cool the stove and then reload, at first that flue will get hot if you operate the stove right. Yes, very soon then the stove temperature will be much higher than the flue and that is how it is supposed to be. But for some reason some folks read that someone had a flue temperature higher than the stove and freak out. Let me give one example though. A few days ago I had a stovetop temperature of 690. Now if the flue was hotter, I would have had a definite problem. However, the flue temperature was 380 degrees, which, if my math is correct, is 310 degrees cooler than the stove.