Is it possible to have a hot stove and cool flue because of poor conditions (whatever they may be) as one might think the stove and flue would both be cool under less than ideal conditions.
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corey21 said:
Is this a surface thermometer? If so, this translates to 450 to 570°F interior flue gas temperatures. These are totally normal flue surface temps.
(If this is a surface thermometer and not a probe thermometer.)
Perhaps with soapstone stoves - my stove holds its temp for a long time - some hot coals right now with surface temp of just under 300* and internal flue temp of 320* or so. I bet that my stack becomes cooler than my stones before long. But, with steel or cast, I'm guessing the this is less likely to happen, and stack should be hotter than (or perhaps nearly equal with_ the stove temp. Smarter folks will correct my thinking! Cheers!oldspark said:
probe reads 300 to 380. i have a probe and a surface thermo surface one reads 200 to 250.BeGreen said:
Ah, best to describe it as a probe thermometer then. It's a little on the cool side, but not unusual for shoulder season burning. Give it a little time to learn your stove and wood better. When the temps drop the draft will be stronger and if the wood is under top cover, it will be a bit drier too.
i think i should relax then. i am concerned about creosote but it was at those temps last night and i had a great secondary burn going.BeGreen said:
At those temps I think you might have a cresote problem but maybe it will get better the colder it gets. My flue temps will get away from me if I do not watch it.corey21 said:
300-400 is way too cold inside the flue during proper clean combustion of a non-cat EPA stove. Something is not right. I predict that somewhere along the line the quoted 300-400 is actually the surface temp of the flue which would correspond to 600-800 inside the flue which is proper.
I tried to get my flue temps above 600 today and I couldn't do it. With the side door cracked and the fire raging - burning small elm splits and 1/2" - 1 1/2" dry ash and elm rounds - I managed to hit 550. I did this gradually because I was firing a cold stove. I got a small fire going, let it die to coals, and then heaped it with small rounds and left the side door cracked. When the flue temps appeared to have peaked, I closed the door and left the primary wide open. The fire continued to rage and the wood was consumed within an hour, but the flue temps dropped quickly to 425.
I kept checking my chimney and after I'd established the first bed of coals and then got flames going strong again, I had almost no visible smoke from the stack. So I'm convinced I'm getting good clean burns. I just don't see high flue temps.
I know I have very dry wood and I know I have a good strong draft.
Maybe my condar probe is bad. I don't know.
I kept checking my chimney and after I'd established the first bed of coals and then got flames going strong again, I had almost no visible smoke from the stack. So I'm convinced I'm getting good clean burns. I just don't see high flue temps.
I know I have very dry wood and I know I have a good strong draft.
Maybe my condar probe is bad. I don't know.
BeGreen said:
I don't know where folks are getting that conversion factor from. I've always read that the internal flue gas temp is twice the external single-wall pipe temp, and my instruments appear to confirm this. Please tell me I didn't waste my money on these expensive devices.
The first photo shows an external pipe temp of 271ºF, while I am simultaneously getting a reading of 603ºF from a high-quality K-type thermocouple probe that plugs right into the back of my IR gun.
The second photo is a little out of focus, but it shows 636ºF on the outside of the pipe and 1281ºF at the probe. Actually, the probe temp was still rising, but the probe itself is only rated to 1295ºF, so I pulled it out before it exceeded that mark and bent over from its own weight. It was bright cherry red in color. You can see that the IR and the magnetic thermo are close enough to each other for government work. The magnetic thermo is a bit sluggish on a rapid rise, it matches the IR much better after the flue temp stabilizes.
Both photos show the internal temp to be more than double the external temp, but I attribute some of this excess to the fact that I still haven't cleaned that pipe yet this season. It has a health 1/8" internal coating of fly ash that's insulating it a bit.
With gas temps exceeding 1200ºF for 30-60 minutes each day, creosote doesn't really stand a chance. And at that temp, the outside of the pipe isn't even close to the UL limit.
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I believe that last winter Condar had posted on their site that the flue gas temp was ~1.5X surface thermometer reading. Since this post below, this appears to be redacted, or perhaps I am just not finding it.
https://www.hearth.com/econtent/index.php/forums/viewthread/51880/
https://www.hearth.com/econtent/index.php/forums/viewthread/51880/
Not sure I care about the internal temp, surface temp is what I and the house interface with, the gas temp could be 5000 degrees as long as the outside is where I want it.
BeGreen said:
Well, I don't know what Condar says or what kind of flue they are measuring, but I took these photos of my plain old ordinary wood stove flue. What my eyes see, my heart must believe.
After several talks with the engineers employed by the supplier of my instruments, I trust these tools 100%. I recently sent my gun back for a minor repair and they checked the calibration of my gun while I was on the phone with them. Spot on, according to them. I purchased the thermocouple from them as well, to make sure it matched for type, and was told it was accurate to about +/- 1% over its entire range. Photo is of simultaneous readings of IR gun and thermocouple plugged into the same device. Magnetic thermo is close. What's to doubt? Internal flue temps in my install are twice the external temps. I imagine that is close to the truth for folks the world over.
Oldspark, I don't know why it is irrelevant what your internal temps are, these are the keys to tweaking your system, not the external temps. Draft is computed using gas temps, not stove pipe temps. After all your recent posts, to tell the truth, I still don't have a clue where you want your pipe temp to be, but I can tell you that if it are getting temps above 650ºF at any time, that is too high, and if you are getting temps any lower than 250ºF at any time before full coaling occurs, that is too low. You will likely run in between these throughout the first 2/3 of the burn, then drop off to below 200ºF... at which time you better fill 'er up if you want a quick, smokeless re-start.
IMHO
Yeah, it's Condar that says the internal temps are 50% more than external and I haven't seen any test close to that claim yet.
Maybe Begreen's antique probe reads 50% since it's so old? :lol:
Maybe Begreen's antique probe reads 50% since it's so old? :lol:
Todd said:
I can relate to that. My old probe is either completely erratic or rock steady depending on what it's plugged into. :coolgrin:
BK I am talking about real world situtations not a computed draft finding, either my chimney drafts enough or it doesnt and I find that out by trying what I have, that is all I ment by not caring about the internal temp. Youhave convinced me the internal temp is double the surface. Not sure why Condar thinks other wise.
This is so funny that no one can figure out where my comments about flue temps come from, not sure how long it would take to put it together from old posts but the flue temp thing is all over the place with different members. Some do EXACTLY like I do and others scorn me for worrying about it, all I wanted was info about flue temps and it turned into somethin else almost all the time.
This is so funny that no one can figure out where my comments about flue temps come from, not sure how long it would take to put it together from old posts but the flue temp thing is all over the place with different members. Some do EXACTLY like I do and others scorn me for worrying about it, all I wanted was info about flue temps and it turned into somethin else almost all the time.
oldspark said:
But you should care because you don't want to wreck your liner with a continuous burn over 1000 degrees internal which would be about 500 for your external thermometer.
Here's a test anybody can do.
Remove one of the screws from your flue pipe and put a heavy duty coat hanger or similar metal rod into the hole. Run you flue temp up to 600º and hold it steady there for about fifteen minutes. Then turn out all the lights, pull out the hanger (gloves, please) and look at the color of the metal. Try to remember how red it looks, and then compare that color to the corresponding color in the chart below. Look at the temperature column on the left and match that with the proper color to get an fair approximation of your internal temp at 600ºF on your external pipe thermometer.
You have to do this in a darkened room, otherwise the ambient light will mess with how red it looks and give you an underestimation of the real temp.
Remove one of the screws from your flue pipe and put a heavy duty coat hanger or similar metal rod into the hole. Run you flue temp up to 600º and hold it steady there for about fifteen minutes. Then turn out all the lights, pull out the hanger (gloves, please) and look at the color of the metal. Try to remember how red it looks, and then compare that color to the corresponding color in the chart below. Look at the temperature column on the left and match that with the proper color to get an fair approximation of your internal temp at 600ºF on your external pipe thermometer.
You have to do this in a darkened room, otherwise the ambient light will mess with how red it looks and give you an underestimation of the real temp.
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Todd said:
Todd, I do believe the continuous 1000ºF UL safety rating is for the actual temperature of the metal, not the gas temps. I had the same single-wall black pipe for my old stove for almost twenty years, and I'm sure I consistently ran it in the 500-600ºF range all that time. That's because I was advised to by every expert I ever spoke to. It was in fine shape when I finally hauled it to the recyclers when I needed a larger capacity flue for the new stove. Exposure to 1000ºF is nothing for steel, especially stainless. The metal parts on the inside of your stove exposed to temps a hell of a lot hotter than that.
Oldspark, I'm certainly not attempting to show scorn for your concern, just poking you a little. I thought you knew me well enough by now I didn't have to put silly emoticons in there to let you know. I think you are showing a lot of intelligence for pursuing this the way you are, I just don't have the inclination to go back over all those posts to rehash it all. You've been at this long enough that I'm sure you'll figure out what you need to know sooner than later and all will be fine.
BK, I do not have a problem with any of your posts, with Pen's help I more or less figured out what I was doing wrong and I still keep my flue temps in the range I want.
I was thinking the same thing but it does seem to be a little on the low side, keep an eye on the chimney for creosote.corey21 said:
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