I would like to agree but I know that turning the air control down on almost all noncats does not reduce the air flow through the stove. Instead, it just limits the primary air which increases the flow through the secondary system. You have very little control with a noncat.
Secondary air is preset and the fixed holes are only so big. But you are right that more air is pulled thru the secondary as you close off the primary as its a balance between the two. The reason people who previously used old fashioned stoves complain about how new EPA non-cat stoves work and the fact that if your wood is not real dry it wont work in a EPA non-cat stove is the fact the air flow is greatly reduced as the design of the stove is such that only a little air is needed. There are now non-cats stoves rated at over 80 percent efficient. Thats pretty good for non-cats. Having said all of that I would still love to get me a Cat stove some day when I get the extra money. And right now I am heating from the basement, I think the more aggressive heat curve of the non-cats I think gets heat up stairs better.
Just re-read your question after reading a post in another thread by Mike Holton. I would say gases exiting the flue need only be hot enough to avoid condensation, probably somewhere around 212f. Now, what that temperature is where most people measure the temperature, on or in the pipe just after the stove is a moving target depending on your wood, your stove, your flue etc
Not sure I understand what you said there, the 212 or 225 temp is surface temp, the internal temp would be higher.
Maybe I didn't write it very well. Devilsbrew asked the question as "gases exiting the flue" meaning where the gases meet the outside air at the end of the flue. Most people don't measure the gas temp at the exit of the flue, might be a good way to do it but not very practical. I had never thought about measuring the gas temp at the exit of the flue and something Mike posted in another thread made me think about her question again.
I get it your post now, "gases exiting the flue" would be difficult, maybe he ment gases entering the flue. Some have have said they would like to know what the temp is at the top of the chimney but not an easy task. A formula for the temp drop per foot of a particular type of chimney would be useful
I agree on this, we cannot read minds when someone is talking about flue temps. The last two days on single wall external I have been running 260-280 temps 20 " up and cruising 400-500 stove top.
I was curious and just checked my single wall pipe, there is a 3 degree difference between 12 inches and 20 inches up the pipe. I was just curious because I have my thermometer on the pipe at 12 inches
I normally check single wall temps with an IR temp gun because the magnetic thermometers are way off typically.
that's what I used a ir temp gun to check the upper part of the pipe I only use that once in a while to check things out, the Condar pipe and stove top thermometers I have are right on the money Every Rutland thermometer I have ever had was way off
Since we know that the temperature of the surface of the single wall flue pipe is roughly half of the temperature of the gasses in the flue pipe we might assume that we only need 106 degree surface temp of single wall pipe to prevent condensation. That would tell us that the internal flue gasses are above the condensation temperature of 212. Well, I am of the opinion that the surface temp of the single wall needs to be over 212 which necessarily means that internal gas temps will be at 425+ throughout the stack to prevent the formation of condensate. This is like a cold beer can sitting on the table. The surface of that can is where the vapors condense, not the air around it.
Every piece of information I have ever read about flue temps and what I have used as a guide line with no creosote problems has been the 225 surface temp to prevent buildup, the "good" burn zone on a probe temp starts at about 340 which would be in line somewhat with the 225 surface temp.
"That's internal flue temps of 212, not surface magnet temperature, to prevent condensation." Highbeam, that quote of yours from anther thread had me confused. In this thread it looks like we are on the same page.
I tried to be more clear in this thread. I was trying to clarify what I was hearing in that other thread. Oh the confusion.
My stove top was only about 250 degrees when I did that check, I should probably do that again when the stove and pipe is good n hot at cruising temp see what the difference is. Right now I'm getting ready to reload here in a few minutes, the pipe at 12 inches is 164 and at 20 inches is a hundred and sixty with air control just over halfway closed, stove top is 270
okay I am confused now because if you need 212 internal pipe temp then you would need 424 on the surface? most of the stuff I have read says 275 degrees on single wall pipe surface temperature, that would equate to 525 degrees internal
I think the case in point is that those recommendations are to prevent condensation near the top of the stack. I sometimes notice icicles hanging off my cap so I know the stack temps are about right.
No, you have it backwards. Internal 212 would be twice as hot as external, so external 106......you know that, just got confused......
