Yet another flue/flu gas thread. Need some clarification.

[JStone]

As some of you may know I recently put a Lopi Endeavor in the upstairs of my home. Upstairs is aprox 1100 sqft. My wife has burned wood all her life in those old but beautiful but non efficient non-airtight wood stoves. She is the non-nervous type, complete opposite of me. Just the way I am I guess. We've already had a chimney fire in our Yukon-Husky Oil/Wood furnace (last year?) and I don't want to go through that again. That was partial to my ignorance with the necessary quality of wood that is needed for proper combustion.

At any rate. I'm trying to figure out the best temperature to burn my flue gasses at. I have a pretty good understanding on how to use a magnetic thermometer on the outside of a single wall stove pipe, keeping the flue gasses about 250F and not much higher than 550F. I understand that the water vapor will condense once dropped below the boiling point of water at to make sure that doesn't happen you need to keep your stack temperature high enough.

I have a double wall stove pipe with a probe thermometer. One of the digital auber unit's. My question remains that what should my flue gas temperature range/max be during start up and cruise? I find the stove pipe on probe gets to 7-800 easily and could easily get up further during initial start ups. Is this okay to do this every time I start a fire and is this normal? Gut tells me yes as long as their's not an excess of creosote built up in the pipes that could cause and uncontrollable chimney fire.

Since flue gasses will be higher in temperature than the surface temperature, what should I go by for proper start up and cruise temperature? I'm starting to think that I should be going by the magnetic thermo on the stove top when the Lopi is at cruise, keeping the stove top from reaching about 700 should keep my flue temperature at a reasonable level. The only true way to tell what the proper temperature should be during cruise is to purchase another probe and put it at the exit on top of the stack.

**Main thing I want others to re-assure me on is 1) Is it okay during start ups to run the flue GAS temperature up to 8-900F for up to 15-20 minutes while stove top temperature rises. and 2) What is a good cruise temperature of the flue GAS since I have no way of knowing the external surface temperature of the double wall pipe. I don't want to produce more creosote when i could easily raise the temperature,and if the probe reads 500-550 the pipe may only be 300? And does this even matter since the probe gives me what the flue gasses are instead of relying on a magnetic thermo most use on single wall pipe.

As I said earlier to ease my mind I think I just may have to purchase a new probe and attach it to the top of the stack and experiment with flue gas temps at the stove vs flue gas temps at the top. Ugh! Or I could just listen to my wife and stop worrying, I just don't want my life possessions to go up in flames.

 

[jeff_t]

I think you should listen to your wife, but caution is a good thing.

I don't think 1000° on start up is uncommon. Once the stove is up to temp and you start cutting the primary air back and rely on secondary combustion, your flue temps should drop. Cruising in the 500° range will keep you in good shape. Once you hit the coaling stage, you will see those temps drop more, but don't worry about it too much. There won't be any smoke left to condense in the pipe.

I don't know anybody that monitors temps at the top. I'm not sure how you would attach the probe, because I don't think you want to drill thru class A pipe. I suppose you could, since it would be outside the home.

Burn dry wood, and check your chimney often until you know your setup and establish good burning habits.

 

[JStone]

Jeff-t I think your right. Listen to the wife. I'll probably end up getting another probe and attach it with a magnet or screwed into the chimney cap, I don't think I want to drill I to the class A either!

 

[WES999]

I have a probe in my double wall pipe similar to the Auber unit, stove pipe is rated for 1000 continuous operation,
so under 1000 is fine. I start closing the air at 875( actually my stove does it for me). If you keep the flue temp at around 900 by gradually closing the air, you will get the stove up to temp quickly.

As for cruising temps they can vary a lot, as long as you are not smoldering and producing smoke out of the chimney
you should be OK.

 

[oconnor]

Your start temps seem good to me. As for"cruise" temps, I concern myself more with maintaining a bright flame in the fire box. Depending on how hot I want the room to get, I use my stove top thermo to advise when to start closing primary air. 400-500 if the room is stable, 700 if I'm cold by way of example.

As long as a bright flame is maintained in the fire box, and the flue is warmed during start up (as you indicate you do) you won't have issues with creosote.

 

[JStone]

Thanks Wes and O'Connor. I just like the reassurance from the community. The best community on the net I might add. The stove dealers rarely give you any info. I think about the people who don't research or ask questions. They basically install it and say "here ya go". Haven't started a fire in the last few days. Next one I am going to focus on getting the stove temp up while maintaining a flue gas temp under 1000F. Then as you said (which is what I usually do) turn down the air gradually making sure to keep a nice flame until I can close it down to 10% open. I find the lopi, at least in mild weather, does not want it closed completely.

 

[oconnor]

The amount of air that can be restricted will vary as you say. I also find that I can close it down more after the flue has warmed completely - 1or 2 hours of burning - than when I start it. Warmer flue means better draft, therefore better ability to pull air in through the secondaries.