Flue Temperature

[disamatic]

curious what people have as a flue temp. 18" up. Also what your stove top temp may be. Thanks!

 

[bobdog2o02]

400° stove, 275° pipe

 

[HotCoals]

That can vary with me from 250 (outside single pipe)450 when firing it up.

If you can get your stack temp down to the same temp as your room you will have 100% efficiency! lol

 

[bobdog2o02]

100% lol.

 

[Highbeam]

Gotta be careful here, the temp of the outside of a single wall pipe is half the actual flue gas temp. Some of us measure flue gas temp directly with a probe.

On my bk I run 400-450 at the one hot spot on the stove top with 400 degree internal flue temps.

 

[Jags]

Highbeam is correct - it is important to state surface or prob readings when stating flue temps.

My 600 probe temp is roughly equal to a 300F surface temp (on single wall). Double wall surface temp doesn't really have any real life useful value.

 

[russb]

Just interested here; is it fairly accurate to say that the surface temp. of single wall, 18" above the stove, is 1/2 of the interior temp? Has anyone tested this?

Is it also standard for internal flue temps 18" above the stove to be equivalent, or nearly so, to the stovetop surface temp., as Highbeam reported?

I'll report my data if this thread is still active when we start burning.

 

[Jags]

Just interested here; is it fairly accurate to say that the surface temp. of single wall, 18" above the stove, is 1/2 of the interior temp? Has anyone tested this?

It is not written in stone, but loosely accepted. There have been some testing from members that even dispute the 2:1 ratio. Lots of factors. How early/late into the burn are the readings taken. Flue wide open during startup, or clamped down an hour into the burn, etc....(time to equalize inside/surface temps)

 

[Highbeam]

Is it also standard for internal flue temps 18" above the stove to be equivalent, or nearly so, to the stovetop surface temp., as Highbeam reported?

That depends on the efficiency of the stove. My old hearthstone on this same flue would have internal flue temps of 800+ with stove top temps of 400. That stove wasted tons of heat up the flue since not only were the flue temps higher but the flow rate of exhaust up that flue on a non-cat is huge since their secondary intake air is full throttle all the time.

My current stove with a cat strips out just about all possible heat while still allowing enough heat to escape up the flue to power the draft. There is no unregulated air supply so cool flue temps and low flows. Some folks with cat stoves can even have a stove top hotter than their flue temps but mine are generally equal once everything is settled in for a long burn.

You want flue temps high enough to power the draft but also high enough that you don't get condensation of flue gas in the flue. The manufacturers of some stoves know that wasting a ton of heat up the stack will ensure good draft (easier to burn well) and clean flues (perceived low emissions). This will lead to happy customers that don't realize that lowering flue temps will decrease wood consumption and extend burn times. It's a trade off that is part of the design. Keep this in mind as you see more stoves represented in this thread.

 

[HotCoals]

If the stove top is 400f I would think the temp in the box would be around double that.
So if I'm 400 on stove top I figure 800 in the box and if my single wall is 300 surface that I may have around 600 in the flue at 18"..but who knows..lol.

 

[fire_man]

The manufacturers of some stoves know that wasting a ton of heat up the stack will ensure good draft (easier to burn well) and clean flues (perceived low emissions). This will lead to happy customers that don't realize that lowering flue temps will decrease wood consumption and extend burn times. It's a trade off that is part of the design. Keep this in mind as you see more stoves represented in this thread.

Highbeam: Interesting point. This might explain why I get 2+ gallons of soot each year from my 15 foot (poorly drafting) flue while burning a stove with allegedly very low emissions. Yes the wood is dried 3+ years. I extended my flue a couple feet, which should improve draft. If my flue is cleaner this year you will be proved correct.

 

[Highbeam]

Highbeam: Interesting point. This might explain why I get 2+ gallons of soot each year from my 15 foot (poorly drafting) flue while burning a stove with allegedly very low emissions. Yes the wood is dried 3+ years. I extended my flue a couple feet, which should improve draft. If my flue is cleaner this year you will be proved correct.

Creosote is condensed smoke right? Perhaps a little particulate matter as well. Smoke and water condense as temps drop. If your chimney is spewing 1000 degree smoke from the cap then I would not expect much of anything to condense in that flue. This is why even folks burning smoke dragons CAN have a relatively clean flue if they are very good about keeping a hot fire.

My BK is a dirtier burner than my old inefficient hearthstone. Dirtier smoke from the cap and dirtier creo accumulations. Same wood, same flue, same house. I don't believe that the older BK cats like mine are optimized for emissions. The newer models have significanltly reduced PPM emissions.

 

[mepellet]

When crossing, my probe thermometer reads anywhere from 400-700 typically.

 

[stoveguy2esw]

when i have the "flue" my temps only seem to get to about 102F. maybe thats why when i have the flue i feel like i have ceosote buildup in my "pipes"

 

[BrotherBart]

What are your temps when you have the "flu"?

 

[NHcpa]

What are your temps when you have the "flu"?

Bada...boomp...

 

[Sprinter]

And at what point in the burn cycle? For my double wall probe-type thermometer, it can go to 900 - 1000F internal at first (more if I'm not watching) until I start to close the air down but then it goes down to around 450 -600 for most of the cycle. I don't know your stove but I let my fire go until the secondaries fire off which is around 1000F flue temp and maybe 300F stove top depending on the fuel load.

 

[russb]

Now I have some data. Regency F2400, cruising surface temp (1 hour after reload) is 480-500, stovepipe temp at 18" is about 225 (surface of single wall).

 

[DougA]

I'm the same as Sprinter, except I've got an older VC w/o a cat or secondary tubes so I didn't think my info may be as relevant. I shut down the primary when the flue hits 900 but it can go from 900 to 1200 in half a minute if you aren't attentive. Once you are in the regular part of the burn, the flue & stove top are pretty much the same on mine.

 

[Cory S]

When the primary air is closed more and more, there should be a higher delta between internal firebox/stove temperatures, and flu up gas temperatures. I can run a stove temp of 500-600*, while keeping flu gas temperatures between 275-300*. Lots of factors will change measurements. Outside air temps, inside air temps, barometric pressure, species of wood, moisture content of wood, stove efficiency, etc etc.

 

[Highbeam]

When the primary air is closed more and more, there should be a higher delta between internal firebox/stove temperatures, and flu up gas temperatures. I can run a stove temp of 500-600*, while keeping flu gas temperatures between 275-300*. Lots of factors will change measurements. Outside air temps, inside air temps, barometric pressure, species of wood, moisture content of wood, stove efficiency, etc etc.

So is your flue meter a magnetic meter? I bet it is and if so your stove temp matches your flue gas temp.typical of non cats.

 

[velvetfoot]

At this moment at 100% output it is 269F.

 

[Osagebndr]

I'm burning an early 80's reg buck. I try to keep flue temps between 350-500,although I have had it rolling at700 that's 10" above stove top just below my double wall pipe. I also have another magnetic thermometer in the left door that reads between 175-350 and I mostly don't have smoke coming out the flue. My burn times aren't the best but it they aren't bad either

 

[Cory S]

So is your flue meter a magnetic meter? I bet it is and if so your stove temp matches your flue gas temp.typical of non cats.

It's actually a IR meter, and the results are pretty much exactly what I described.

 

[DougA]

An IR gun will not give you the same readings as a probe in the flue itself.