Several of you have been graciously answering my stove operation and temp questions lately and I greatly appreciate it. So far I have found out that for the last few years I have been overfiring my stove. I now have a flue thermometer(probe 20" above stove) and stovetop thermometer(mounted on hottest point on top of stove measured with infrared). I have removed a grate in the bottom of my stove that I had previously added. So now I am burning properly I believe. My question- if the stove top temp is say 500-550, the flue is just around 400 or so. The recommendations on the flue thermometer show 400 as the cutoff for ideal combustion. During lower temp burns with the stove damper backed off(stovetop around 400), the flue may only be 300. My understanding is this will create creosote. Which temp should I be more interested in? Keeping both in ideal range, especially for long burns does not seem likely without several damper adjustments during the burn. Is this normal and I'm just not used to it because I've not been reading temps?
Flue temp vs. Stovetop temp- Which is priority?
- Thread starter bjorn773
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
- Status
Corie
Minister of Fire
The stack temp is really the one you should pay attention to. However you need to keep a good eye on what's going on inside the firebox.
Low stack temp, but active secondary combustion and little to no smoke from the chimney? Good burn, even at a low stack temp, how much creosote can possibly condense in the flue if you're only send 3 grams of total particulate matter up the chimney per hour?
Low stack temp, but active secondary combustion and little to no smoke from the chimney? Good burn, even at a low stack temp, how much creosote can possibly condense in the flue if you're only send 3 grams of total particulate matter up the chimney per hour?
Our F400 tends to run this way, not sure why. I have a hard time getting the stack temp over the stovetop temp. At times I wonder if the Condor is accurate. But like Corie said, it seems to be burning quite cleanly.
webbie
Seasoned Moderator
I guess you get all sides of the story here!
If the stove is single wall (the top), I like to monitor the temp of that part....because that is what has the most bearing on the actual heat output you are operating the stove at.
Stack temp might be more for those who like a lot of gauges and gadgets, but there are so many factors that affect this (ash buildup inside pipe, stage that wood is burning, etc.) that I prefer the stove top.
Truth be told, we usually had one thermometer on each (the stove top and the stack).
If the stove is single wall (the top), I like to monitor the temp of that part....because that is what has the most bearing on the actual heat output you are operating the stove at.
Stack temp might be more for those who like a lot of gauges and gadgets, but there are so many factors that affect this (ash buildup inside pipe, stage that wood is burning, etc.) that I prefer the stove top.
Truth be told, we usually had one thermometer on each (the stove top and the stack).
Yeah I had a probe in the pipe on the 30 until I changed liners and finally got a stainless elbow for a stove adapter. I didn't want to poke a hole in the elbow even though being an old turbine engine guy exhaust gas temp tells me more about combustion than anything else. A year from now the stove top thermo will probably be gone too.
BUT this does raise a question for the class, and of course our favorite stove engineer. With a free stander or an insert, either one with a blower, after the stove is up to temp and you fire the blower should you bring the stove top temp back up. Example: With the 30-NC the stove can be rolling at 550 and when the blower is started, even at a low speed, the thermo is going to drop back to around 450 as the air blows across the top of the stove. No perceptible change in the burn.
Should the stove be fired to bring the stove top reading back up to 550 or just let it cruise?
BUT this does raise a question for the class, and of course our favorite stove engineer. With a free stander or an insert, either one with a blower, after the stove is up to temp and you fire the blower should you bring the stove top temp back up. Example: With the 30-NC the stove can be rolling at 550 and when the blower is started, even at a low speed, the thermo is going to drop back to around 450 as the air blows across the top of the stove. No perceptible change in the burn.
Should the stove be fired to bring the stove top reading back up to 550 or just let it cruise?
jpl1nh
Minister of Fire
Correct me if I'm wrong, but it's my understanding that the fireboxes are designed, especially in secondary burn units, to reflect and concentrate heat within the combustion area to help achieve the higher temperatures necessary for complete combustion. I would think that the stack temperatures would always be cooler than the firebox and stove top as the air expands upward, and since heat has already been expended into the surrounding stove, stove pipe, etc. Maybe Corie could clarify that and why or why not. I know in my cat stove, typically as the cat engages my stack temps drop to around 300 while I know the cat is acheiving as much as 1100-1200 degrees only a couple of feet upstream from my stack thermometer(which is not a probe so it may be reading cooler than the actual gas stream) Bjorn, I would say what you really want to avoid is temps up over 700 either stove top or stack, and below 250 stack temp with an active pre-coal burn going on. Just my .002 cents worth. Yes, you might ideally need to adjust your damper a few times throughout a burn cycle to maximize efficiency and minimze wasted flue gasses, but I think with a bit of experimenting and observation you'll learn what your best overall setting is for long burns. Factors such as outside temperatures, wind, the wood your using may affect those settings slightly but you'll learn that too. The several damper adjustments you might make during a daytime long term burn probably won't dramatically improve your efficiency over the one time setting you learn to make.BeGreen said:
Bill
Minister of Fire
bjorn: My stove top running 400 and my chimney therm says about 300 also. It's still fairly early in the heating season, it will run different when its 0 outside. When I start my stove up it's not unusual for me to hit 800 degrees inside the chimney, I cut the damper down at that point. I always thought it was a good idea to let the chimney rip once and a while to clean out the crud.
Highbeam
Minister of Fire
Other than creosote formation I don't really care what my stove pipe temp is. Why should I? Maybe I'm missing something. It can take very high temps but the stove itself is limited to relatively low temps and is also the source of heat so I want to know how hot it is. I do like gizmos though so maybe someday I'll consider it. If you're only going to choose one thermometer then by all means go for the stove temp.
Metal said:
How long to you think those snap-together tin stove pipes from the hardware store can take 1000 degrees Metal? For that matter 24 gauge single wall Dura-Black?
Bb let me take a shot at answering your concerns even when the fan kicks in the fire box will be the same temp its just extracting the surface temp by passing air over it
bjorn773 all the talk is about the damper setting and dropping temps there is still the primary air control that can be adjusted to add heat without adjusting the damper and it will promote more secondary combustion with the damper closed naturally the vent pipe is going to cool with the damper closed after all you want the stove to retain as much usable heat as possible
I'd say keep the two thremometers and watch the both experiment and learn how to find the sweet spot of good heat production little creosote and longer burns
bjorn773 all the talk is about the damper setting and dropping temps there is still the primary air control that can be adjusted to add heat without adjusting the damper and it will promote more secondary combustion with the damper closed naturally the vent pipe is going to cool with the damper closed after all you want the stove to retain as much usable heat as possible
I'd say keep the two thremometers and watch the both experiment and learn how to find the sweet spot of good heat production little creosote and longer burns
stoveguy2esw
Minister of Fire
Corie said:
corie hit the nail on the head, not much creo formation when the carbon solids are dang near all burned away, as for the concentrated heat section of the unit , usually these areas are not directly against the top of the stove and the top is protected by a thermal blanket or baffle of some kind. stack temps do generally run a bit lower in a reburn unit (but not all cases) i have had stack temps with my old AC at 800 and up when the cat was hitting about 1200, both readings with a condar probe one on top of the cat and the other 18 inches up the flue and have had temps as low as 300 with 700 on the cat. but even when i wasnt ripping the stove in the dead of febuary, i still wasnt getting any appreciable buildup in the flue, even with a 10 year old applied ceramic (still my choice as the best out there) catalyst.
derbygreg
Member
OK I chose to put the thermostat on the stove especially considering I have a double or triple wall stove pipe.
What temp approximately should the stove top run at during a normal burn I have a non cat Quadrafire Isle Royale?
What temp approximately should the stove top run at during a normal burn I have a non cat Quadrafire Isle Royale?
I should clarify here, I have probably been using improper terminology. I do not have a "damper" in the stove pipe. When I have been "backing of the damper", this is the primary air. This is the only control I have of the air as the secondary pulls through non-adjustable intakes on the lower rear of the stove.
MichaelS
Member
I monitored both last year. I found my Stove top runs hotter than the stack. If I have the primary air 100% open for start up the flu temp. would stay pretty even to what the stove top was until I shut the air down.
Burn-1
Feeling the Heat
derbygreg said:
Greg you will be surprised how warm the griddle top on that Isle Royale will run. I have my thermometer on my stove pipe with my Isle Royale so I can sleep better.
derbygreg said:
Carpneils can provide some direct experience under cold conditions. But about 550-650 is normal.
derbygreg
Member
BeGreen said:
Thats sounds good, It has been lit for a half hour and is already 500 plus degrees!
From what I remember, Neil likes to run his hotter in the winter. But I'll let him answer that. Keep us posted on how the stove is working for you and put up some pictures!
- Status
Similar threads
