Finally got to burning my new lopi 1750 stove this weekend and its been great. Been having some trouble getting a good secondary burn tho. Ive been trying to keep the stack temp in the range around 400 or so but when i cut the air way back i drop below that. At what point during the combustion process os alright to not worry about the stack temp being hot enough?
Stack temps vs stove top temps?
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lsucet
Minister of Fire
I will say at the coal stage. You will need more temperature than that to get secondary. Try letting it go around 600 and see. Cut the air in steps, 3 to 4 steps before completely closed.
Not all install are the same and maybe yours don't require to cut the air all the way back.
Careful, 600 skin temp corresponds to 1200 degrees internal which is over the redline for class a pipe.
So often people mix up which flue temp we’re talking about. Internal vs. surface.
lsucet
Minister of Fire
And you are right. I used to have years ago those when I was using an old stove with single wall, I remember the condar one is between 400 and 500 the range where the flue temperature should be but I remember the other one the flue range is up to almost 600. I should have them around in some place.
So your saying that my stack thermometer actually is wrong and whatever the thermometer says its actually double that inside the pipe?
Heres a few pictures of the install and the thermometers im using. Another question, lopi calls for 15' of chimney height bit from the Manuel it measures that from the floor that stove sits on not top of the stove? From the top of the stove i have about 14' now.
![[Hearth.com] Stack temps vs stove top temps?](/talk/data/attachments/230/230121-a02499deaae26e3d8417dc41b9d77a7e.jpg?hash=N3aMjOVaX-)
![[Hearth.com] Stack temps vs stove top temps?](/talk/data/attachments/230/230122-60bac1f3734c16d74489da51db8d75f6.jpg?hash=5q_ncxNgb7)
![[Hearth.com] Stack temps vs stove top temps?](/talk/data/attachments/230/230123-804e8b6cc2d366b749df80853f200f06.jpg?hash=e6aPlXcZ5p)
Both measurements of flue temperature are correct but they’re different measurements. Like Celsius and Fahrenheit. When taking or giving advice you must know which measurement is being used.
For example, my last noncat was a hearthstone and I regularly ran internal flue temperatures up over 1000. If you ran your stove such that surface flue temps were over 1000 then you are actually at 2000 internal temperatures and that is way too hot.
Many modern surface meters have suggested ranges for operation now that are reasonably good.
Ok i get what your saying, as long as i stay in the range that the thermometer says i should be ok, i guess what i was trying to get at is once the load of wood has pretty much burned down and the temps dip below the range is it burning dirty or is it clean?
After the fuel is spent or mostly spent then it is normal for flue temps to drop below those temperatures required for clean burning early in the burn. Ultimately flue temps of zero are very clean when the fire goes out.
At any time, if you think you are burning too cold to be clean go outside and look at the stack emissions. As long as they are clear, you are clean burning and not mucking up your chimney with creosote.
Stack emissions are a better indicator of clean burning than meters.
No red line for class a pipe is 2100 degrees. But i agree 600 surface temp is to hot. I start shutting back at 400 and try to keep it under 450. Cruise around 275 to 300.
Highbeam is right on. After most of the wood is spent and you are burning charcoal the temp can drop with no concern about creosote.
Class a chimney is only rated for continuous flue gas temperatures of less than 1000 degrees. Quick google search. Safety first.
Key word is continuous. During chimney fires or other short term events, class a can take more.
I suppose the term “red line” means different things to different people.
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I know very well what the temp limits of stainless class a chimney is.
And most reasonable people know that redline is the highest safe limit of something. Not nessecarily top continuous limit. Try running your car at its redline for an hour or so and see if it is the safe continuous limit.
I’m confused, 1000 degrees is the max continuous rating of class a. Not sure what you’re talking about anymore.
Yes it is max continuous. Not the max. Nothing saying you cant run up over 1000 every time just cant run there all the time.
And i was using the example of your redline analogy which is an automotive term. I absolutly agree that you cant run at 600 external temp on single wall all the time. But the op isnt doing that they are running at 400 which is perfectly safe. I agreed with everything you said other than the redline thing. It was just inacurate terminology. I was simply trying to make sure things were clear no need to get defensive.
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