Taller stack=higher flue temps?

[graycatman]

Imagine two setups that are exactly the same: same stove, running at 600 stovetop, same wood, same house, same weather conditions, etc. The only difference is one has a 15' stack, and one has a 30' stack. so, everything else being equal, would you expect to see higher flue temps in the setup with the 30' stack?

I have a 30' stack-14' of Selkirk DSP with 2 45's at the top separated by a 1' straight piece, into 16' of Metalbestos straight up. I find that to run a stovetop at 550-600 my stack has to be at 700-750 (Condar probe). I ask the question because I often see non-cat owners reporting stovetops well in excess of their flue temps, and I can't seem to come close. My wood is good (20-24 months c/s/s, no oak, a lot of locust).

 

[oldspark]

That's still way lower than my flue temps and you cant compare a cat to a non cat, different breed of animal.

 

[begreen]

Yes, when the stack is tall and the draft is strong, it can pull too much heat up the stack. This is a good case for a draft damper and or slightly more restriction of the air intake.
FWIW, if this is a new style Condar probe, I wouldn't bet my life on the reported flue temps.

 

[btuser]

higher stack = more draft = stronger pull = more heat up the chimney = higher stack temp.

All things being equal

 

[wkpoor]

Well then explain this. I have 41' from stove top to cap. I have had 5 different stoves on this chimney in the last 11yrs. And my surface temp measured 18" above stove outlet normally runs about 250 with a 600 degree stove top. Only way to get stack temps up is open the primary and let yellow flames roar. Once I shut down the primary and run on secondaries then the temps fall fast and cool right off. About the highest I can even get to is 600 with the primary wide open and stove top over 800.

 

[oldspark]

Glad you posted wkpoor, as YRMV, my chimney is 21 feet total and I have high flue temps all the time and dont like it, the old Nashua had much lower flue temps.

 

[begreen]

One of the big problems here is that folks try to project one solution for all situations. There is a huge amount of variables involved. Every home, stove, flue, location, climate, position in the house vs the prevailing winds, fuel, is going to affect the stove and flue temps. And then there are complicating factors like suspect instrumentation and the all too prevalent human factor. This makes some comparisons folly.

 

[jdonna]

One of the big problems here is that folks try to project one solution for all situations. There is a huge amount of variables involved. Every home, stove, flue, location, climate, position in the house vs the prevailing winds, fuel, is going to affect the stove and flue temps. And then there are complicating factors like suspect instrumentation and the all too prevalent human factor. This makes some comparisons folly.

+1

The pressure plane plays a role as well, negative, neutral or positive.

 

[oldspark]

"One of the big problems here is that folks try to project one solution for all situations"
Bingo to that Bro!

 

[ScotO]

One of the big problems here is that folks try to project one solution for all situations. There is a huge amount of variables involved. Every home, stove, flue, location, climate, position in the house vs the prevailing winds, fuel, is going to affect the stove and flue temps. And then there are complicating factors like suspect instrumentation and the all too prevalent human factor. This makes some comparisons folly.

+2...like you said here, every single situation has a different set of variables...but a good post, nonetheless......brings up some good points to consider.

 

[ScotO]

I do imagine, in situations where you are getting high stack temps, that you could install in a damper as stated earlier. But even in a particular install, that damper may not always help the situation (due to outside temps, high/low pressure systems, wind, etc). So, as with everything else a woodburner has to consider, there would be a learning curve in every single individual application.