Stove temp increases to 800 ° in the fire Box and flue temp lowers to 300 °

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Hiram Maxim

Hiram Maxim

Minister of Fire
Nov 25, 2007
1,065
SE Michigan
My Buddy's big monster stove was loaded up this morning and after it heated up to aprox. 500 ° he watched the Stove temp increases to 800 ° in the fire Box and flue temp lowers to 300 °??

He is going what the hell?

Anybody have this sort of reaction? He was burning well seasoned red oak for maximum btu output during this cold snap.

Also he said that he went out side and it looked like white smoke was billowing down from the chimney but he didn't smell smoke! is this moisture from the wood and the cold temps?

Anybody experience anything like this?

Thank you,Hiram
 
That's how our PE works. After reducing primary air, secondary burn gets going strong. The firebox and stove get hotter, yet the flue temps drop. It's not unusual for us to see 750 stove top and 450 flue temps after feeding a full load in the stove.
 

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You know you are a Hearth addict when you have performance charts for your stove that you made yourself. I wish I could do that....

Great info BeGreen.

My guess is that closing the air down lets the air remain in the frebox longer, and therfore more of the heat is transfered to the stove. As well, there must still be combustion occuring in the gasses when the air is open, and once closed and with the reburn kicking in, that combustion occurs in the firebox, and cooling can occur as it exits the stove.
 
That's perfectly normal for an EPA stove. They design them to keep the heat in the stove and just enough heat up the stack to maintain good draft. My stove top can reach 700 while stack temp is only 300.
 
Even my old smoke dragon does that when the fire reaching that mix between active wood flaming and coaling. Just not so drastically and of course, I cannot see the "northern lights" as many of you can. "OOOOZing with jealousy"

pen
 
I have had a lot of white "smoke" as well on cold mornings, and was mildly concerned until I looked at my neighbor's chimney. He has a natural gas furnace, and was putting out more white "smoke" than me. Nothing more than water vapor hitting that cold air.
 
Thanks guys! Really appreciate it.

Hiram
 
BeGreen said:
That's how our PE works.
Click to expand...
I've got a question about that graph. At 10am you have 550 in the flue dropping to 150 over 6.5 hours. At 5pm you have 550 in the flue dropping to 200 over 9 hours. You're gross heat output (stove top) was greater on the second cycle than the first cycle yet the first cycle was full up and the second cycle was just 3 splits. How do you explain that? What are you doing different between these cycles that makes the second one burn less wood over a longer period and still yield a higher BTU/hr figure?
 
I am going to say that there was a better bed of coals. Also at 5pm the flue (all the way up) is heated and so is the stove, theirfor no heat is wasted trying to heat a cold flue or stove.
 
PunKid8888 said:
I am going to say that there was a better bed of coals. Also at 5pm the flue (all the way up) is heated and so is the stove, theirfor no heat is wasted trying to heat a cold flue or stove.
Click to expand...
That can't be right. On the first cycle he would have already had coals from the night before (most probably). Then he started a fire at 8:30am. That fire warmed the stove and flue. Then at 10am the pre-heated stove was loaded. With the second cycle, on the other hand, the stove wasn't at operating temperature when it was loaded.
 
bokehman said:
BeGreen said:
That's how our PE works.
Click to expand...
I've got a question about that graph. At 10am you have 550 in the flue dropping to 150 over 6.5 hours. At 5pm you have 550 in the flue dropping to 200 over 9 hours. You're gross heat output (stove top) was greater on the second cycle than the first cycle yet the first cycle was full up and the second cycle was just 3 splits. How do you explain that? What are you doing different between these cycles that makes the second one burn less wood over a longer period and still yield a higher BTU/hr figure?
Click to expand...

Neither our wood species, nor our wood split size is consistent. Also, the first cycle was a warm up the stove and house cycle. Once the stove is fully up top temp, the EBT seems to work better. This graph mostly illustrates that with reduction of primary air, flue temp go down, while the stove top temp continues to go up. To be really meaningful I would need to plot a graph of several days of burning. Maybe later.
 
BeGreen said:
That's how our PE works. After reducing primary air, secondary burn gets going strong. The firebox and stove get hotter, yet the flue temps drop. It's not unusual for us to see 750 stove top and 450 flue temps after feeding a full load in the stove.
Click to expand...
Boy, if I made a chart like that, no room for all the "load splits" points.
I need a new stove. DOH!
 
BeGreen said:
That's how our PE works. After reducing primary air, secondary burn gets going strong. The firebox and stove get hotter, yet the flue temps drop. It's not unusual for us to see 750 stove top and 450 flue temps after feeding a full load in the stove.
Click to expand...

How are you reading those flue temps???? With a probe or surface mount thermo??? Double or single wall if surface mount?? Just curious as my PE spectrum acts the same way but my flue temps are so much higher.
 
double wall flue, probe thermometer... softwood.
 
BeGreen said:
double wall flue, probe thermometer... softwood.
Click to expand...

Your chimney isn't very high, is it??? I can't get my flue temps below 600 with the secondary kicked in and air shut all the way down. Actually, my stovetop and flue gas are usually pretty close, most of the time flue is higher...
 
About 19' tall. But I have a pair of 45's for an offset right above the stove to align with the HT flue. That may be slowing things down a bit. Have you considered adding a flue damper?
 
BeGreen said:
About 19' tall. But I have a pair of 45's for an offset right above the stove to align with the HT flue. That may be slowing things down a bit. Have you considered adding a flue damper?
Click to expand...

Already did, right at the stove connection. I got about 6 1/2' Double wall into a 25' or so HT-103 chimney. I can tell the damper makes a difference but obviously, it's not enough. I only have it open during reloads to suck up the smoke and for 10 minutes or so after I load up. The rest of the time she's completely closed. And no, I've checked and checked and checked and I have no gasket leaks or other air leaks. I hate seeing all that heat escape up the chimney but I don't know what else to do... Here's a pic of my setup.
 

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