Question on stack temp

[NH_Wood]

Hi everyone,

I've got a good load burning now - strong secondaries. Stove top cruising at 500*. Question on my stack temp. Reading 700* degrees. Primary air completely shut down and stovepipe damper closed 1/2 way. Should my stack read that high, or am I losing a lot of heat out the stack? Thanks! Cheers!

 

[oldspark]

I dont know much about stack temps but have read a lot :lol: , I assume this is a cold stove and a new fire, after the stove gets good and hot for a while the stack should come down and be lower than the stove top, that is the way my stove works, some days it could take a hour or 2.

 

[precaud]

What you describe seems improbable, unless you loaded your stove with small splits and they're taking off. How, and where, and with what, are you measuring 700º?

 

[oldspark]

What you describe seems improbable, unless you loaded your stove with small splits and they're taking off. How, and where, and with what, are you measuring 700º?

Why do you say that, it is very possible on start up and reload, why do some of you think that is not possible?

 

[precaud]

spark, I know you have a thorn up your rear on this issue. Chill, please, I'm trying to help sort it out. The post started with "I’ve got a good load burning now" so I'm just trying to get more info. It's impossible to be precise yet with the limited info we have.

 

[oldspark]

spark, I know you have a thorn up your rear on this issue. Chill, please, I'm just trying to help sort it out. The post started with "I’ve got a good load burning now" so I'm just trying to get more info. It's impossible to be precise yet with the limited info we have.

OK, there is another assumption, why do you think I have a thorn up my rear, not very hard to have a higher flue than stove top under certain conditions and wanted to know why you think it is not possible? Who has thorn?

 

[precaud]

I don't want an argument. Let's keep this on topic.

 

[oldspark]

Trying to but you are making it hard when you say things like that?
Possible reasons for higher flue temp than stove top
New fire
reload
primary air open too far

 

[oldspark]

precaud, I thought by answereing my question about why you think it is not likely it would help the OP and me.

 

[Backwoods Savage]

Hi everyone,

I've got a good load burning now - strong secondaries. Stove top cruising at 500*. Question on my stack temp. Reading 700* degrees. Primary air completely shut down and stovepipe damper closed 1/2 way. Should my stack read that high, or am I losing a lot of heat out the stack? Thanks! Cheers!

Oldspark, perhaps some working has given some wrong ideas between you and precaud. Precaud perhaps took something wrong or maybe both but let's not let this get between you guys.


NH_Wood, while those temperatures are entirely possible, if you are measuring temperature on the outside of the flue I would say it is not normal. With our stove, with a 500 degree stove top our flue would more than likely be 300 or below (but we also have a cat stove). Most folks will find at the point you mention that the flue temperature will drop way below 700.

Definitely right on a reload or starting from cold that flue temperature then is very normal, but even then, we do not let our flue get that hot. We typically do not go over 500-600 degrees on the flue reading. So with your flue reading that high it begs the question on if you may have a possible air leak somewhere.

I don't know the details on your stove but I do remember someone commenting on some stove about the draft being on a slider (like Woodstock's) and somehow it had gotten off the track. That meant when they thought the air was shut down it really wasn't. It was a simple thing to put it back on the track and all was well. That is just something for a possibility.

Hopefully you have checked all gaskets and perhaps you've also done the test with match or incense going all over the stove to try to detect any leaks. Let us know how you come out with this.

 

[oldspark]

Backwoods, I have no idea what the deal is with precaud, I can very easily get these kinds of temps until the stove settle in which can be a hour or 2.

 

[Backwoods Savage]

I think he was probably referring to this from the OP, "I’ve got a good load burning now - strong secondaries..." Meaning that this not after a reload or a cold stove starting. Also, most folks do not get those flue temperatures (if measuring on the outside of the flue) for an hour or two. For sure ours does not. But nonetheless, I'd just let that conversation die and forget about it totally as I really do not think either of you intended on it going south. Methinks both of you are too smart to let that happen.

 

[vvvv]

WOULDNT I LOVE TO STICK A MAGIC HEAT ON IT! VCBURNER [member] should have some post related to MH+EPA forthcoming....meantime why not blow a fan on the flue & observe changes in the fire?

 

[Backwoods Savage]

Forget the magic heat junk. Pook (the above poster) is sort of a weird on on this forum (sorry Pook, just stating the obvious) who likes to push the magic heat. In my book it is one of the worst things one can do to install this thing. Bad news all the way around. You can even do some searching on this forum about it.

 

[oldspark]

I think he was probably referring to this from the OP, "I’ve got a good load burning now - strong secondaries..." Meaning that this not after a reload or a cold stove starting. Also, most folks do not get those flue temperatures (if measuring on the outside of the flue) for an hour or two. For sure ours does not. But nonetheless, I'd just let that conversation die and forget about it totally as I really do not think either of you intended on it going south. Methinks both of you are too smart to let that happen.

Glad you chimed in, I get those flue temps in a very short time and have secondaries just like the OP is seeing, this is what confuses me I thought seeing those high of flue temps in a short time was normal. Trying to stay on the OP's subject here.

 

[precaud]

It appears the OP has sensibly abandoned ship. Don't blame him, it's been hijacked.

Spark, the fact that you can operate your stove in such a way as to get higher stack temps than stovetop temps, doesn't mean that it's desirable. That's why I say, it's a silly argument. And we've already hashed this topic out in another thread.

Until we get more info from the OP, we can't do anything but speculate on the cause.

 

[oldspark]

It appears the OP has sensibly abandoned ship. Don't blame him, it's been hijacked.

Spark, the fact that you can operate your stove in such a way as to get higher stack temps than stovetop temps, doesn't mean that it's desirable. That's why I say, it's a silly argument. And we've already hashed this topic out in another thread.
,
Until we get more info from the OP, we can't do anything but speculate on the cause.

I am telling the OP i see the same thing so thought it was revelent, I have no desire to have high flue temps, If I am hyjacking this thread some one tell me so but that also include a ton of others, just trying to help the OP with all the info possible. :-/

 

[precaud]

If I am hyjacking this thread some one tell me so

OK. You are hijacking this thread, please chill and wait until the OP gives us more info.

I can honestly say, you asked for it.

 

[Battenkiller]

I've got a good load burning now - strong secondaries. Stove top cruising at 500*. Question on my stack temp. Reading 700* degrees. Primary air completely shut down and stovepipe damper closed 1/2 way. Should my stack read that high, or am I losing a lot of heat out the stack? Thanks! Cheers!

Sounds pretty high to me. I like to see max temp on my old dragon to be below 650º. Sometimes it gets away from me, but never had it run away once the bypass in closed.

Closing the stove pipe damper will without a doubt cause your stack temps to rise dramatically. You are containing heat that would otherwise be going up the stack. Of course, it depends on which side of the pipe damper you have that thermometer.

If the thermometer is above the damper on the pipe, high temps would indeed be very unusual. My feeling in that case is that those strong secondaries are sending up a lot of excess heat up your flue, and yes, it is being wasted. Sure, you need sufficiently high flue temps to draw air in, but you've got to have excess draft going on with temps that high.

You say you've got the primary air shut down all the way. Sounds like you have a lot of secondary air being pulled into the stove by that draft, exacerbating the problem. I suspect that with all that stone on top that there will be a pretty good lag time, but the same secondaries that are excessively heating up your flue will cause that top to catch up after awhile.

If this is a one time event, I would just ignore it. Wood stoves are capricious in nature. No one can predict exactly how every load will burn, or how the logs inside will fall as they burn. You can be running the stove just at the edge of runaway all the time and never know it until a few key things fall into place at once and all of a sudden the stove has a mind of its own. If this is a frequent occurrence, however, I feel there is something that needs to be addressed.

 

[Todd]

Hi everyone,

I've got a good load burning now - strong secondaries. Stove top cruising at 500*. Question on my stack temp. Reading 700* degrees. Primary air completely shut down and stovepipe damper closed 1/2 way. Should my stack read that high, or am I losing a lot of heat out the stack? Thanks! Cheers!

If those stack temps are internal I say your alright, if external too high.

 

[begreen]

FWIW, different stove designs are going to give different results. The temps being reported are similar to what Highbeam has reported. Could it be that some Hearthstones let a bit more heat up the flue? I think so. This seems like a whole lot of angst over nothing.

Also remember that there has been reported a similar variance with different thermometers. Last year we saw a crop of new Condar probe thermometers reading +100 from a calibrated thermometer. If the OP is actually getting +600 temps inside the flue during peak secondary burn, that doesn't seem like something to get excited about. Could be just strong draft. If the flue is tall and draft hard, try closing the key damper all the way. It will still draft.

 

[NH_Wood]

Wow! Just returned from a day of work and checked my post. Sorry to have caused a commotion! Anywho = back to topic. I get these temps regularly - at cold start, reload, and during the burn. I'm measuring the temps using an internal probe, above the damper. I've found that if I begin to close the primary air earlier in the initial burn, I can keep the stack at ~ 600* or below - but - still early on in the burning process - not sure what it will do in the middle of winter with stronger draft. Ckdeuce was helpful in providing his stack temps with his Mansfield (similar to mine) and providing a link to a Highbeam post - again, indicating stack temps similar to mine. So - perhaps BeGreen is correct - Hearthstone stoves might lead to this situation. I also agree that there is a long lag between seeing high stovetop temps even though the stack is quite hot early in the cycle - a fact of soapstone I'm sure. Doesn't take long for the stones to get warm and throw heat, but does take a while for the stove top to get hot (500* or so). Ultimately, I hate the idea of losing too much heat up the stack - perhaps with some tweaking I'll figure out how to keep the stack temp lower. I do have an unusual setup. My stack is tapped into a masonry chimney flue - flue is oversized clay tile (11"X8"), interior chimney going through 2 floors. Draft is good - perhaps too good. I know that I should be venting to 6" pipe, but the flue also services my fireplace (stove tapped into flue on opposite side of fireplace in an adjacent room - I don't burn the two at the same time). Perhaps I have too strong a draft with the larger flue, which is why I made sure it install the pipe damper for more control. I really had no other option for the install - either would have had to line the clay flue and lose my fireplace (wasn't an option) or send the stove pipe through the 1st and 2nd floor ceilings and out the roof (not remotely in the budget). So - I thought it important to include this info for other folks reading the post. Oldspark - thanks for the input. Precaud - no worries - we're all here to help to burn better. Dennis - thanks for the input and PM. Cheers!

 

[Todd]

I think your fine with those internal temps. If your using the Condar probe it's right in the orange colored normal range.