Woodstove pipe temperature

survriggs · Feb 13, 2006

I have a Schrader wood stove with the pipe that goes vertical through the ceiling and into triple-wall stainless. I have a magnetic thermometer that attaches to the pipe. It gives an ideal temperature ( I think it is 300-400 degrees). My question is at what height above the stove should the thermometer be attached? There were no instructions for the thermometer. I have it 18" above the top now. thanks in advance for any information.

Boondox · Feb 13, 2006

That's about where I put mine.

scott_vt · Feb 13, 2006

The ones that I have seen are about 18" to 24" away from the exit of the stove, I think you should be fine were its at now. I dont have one on my stove but for the money they are a good investment!

scotty

PA John · Feb 13, 2006

Survriggs, I had a Hitzer wood stove with a vertical pipe. It was used for several years. The Pipe from the stove was double wall and became tripe wall stainless when it connected at the ceiling into the second floor. I think single wall would get awfully hot. You indicate a temp of 300-400 F. Put the double wall on and scrap the thermometer. PAJOHN

db2 · Feb 13, 2006

Play it safe. A thermometer gives you an indication of the flue temperature. Too hot and you will ignite any creosote present. Even a chimney fire in a triple walled chimney is not a good thing. Use a probe type thermometer on single, double or triple walled pipe.

Just my 2 cents.

Highbeam · Feb 13, 2006

You want the "ideal" temp to be maintained to prevent the formation of creosote. At that temp, the smoke is hot enough to prevent condensing on the pipe before it leaves the top. The real die hards actually have measured the temperature at the chimney outlet to know that the smoke hasn't cooled to the creosote point. I use the thermometer as a creosote prevention and efficient burn temp.

The temperature that is "ideal" varies on the installation. In general, a short chimney doesn't need the high stove temps to keep the smoke hot all the way out. The long chimney needs a hot fire to prevent creosote. Longer, well constructed, chimneys improve draft.

If your pipe is single wall then just above the stove is fine. If double wall or triple, I would plant it on the top of the stove which should be the hottest part. A decent chimney sweep will measure exit temps of the smoke so that you can discover your own ideal temp.

PA John · Feb 13, 2006

Dave, I agree that it's always better to be cautious. I have found that if you burn hard, a horizontial flue will stay cleaner than a vertical pipe to the chimney. If I had a temperature gage and saw it rising and heard the rush from the cresote fire I would close the air off to the chimney, open a window to get the smoke out, put the fire out in the stove. Then consider the fire department and hope the fire is contained within the pipe. I am not sure the temperature gage would be very helpful at this point. By the way--been there and done that.

survriggs · Feb 13, 2006

( Put the double wall on and scrap the thermometer. PAJOHN )
PAJOHN: Good idea but with the higher temps coming from the single wall pipe I believe I am reclaiming some of the heat that would otherwise be lost out the chimney with the double pipe. In fact I am trying to figure out some fabricated attachment with a small blower to reclaim even more of the pipe heat.

Thanks everyone for the helpful comments. I don't post very much but when I need to know something, tractorbynet is where I go. I've learned a lot from you guys.

JimR · Feb 13, 2006

You don't want to cool the pipe too much or you will lower the temperature to the point where you may creat creosote. If you burn one hot fire a day it will burn off any creosote in your chimney. My woodstove at the old farm has been running continuosely since December. I burn it off once a day by running it up in the 500-600 range for 20-30 minutes. Sometimes it has hit 700+ when I wasn't keeping a close eye on it. I only use a single wall pipe right into the chimney flue through the damper plate that I modified.

survriggs · Feb 13, 2006

JimR:
Point well taken. Seems like I read somewhere that if you burn an aluminum can in the stove it will loosen up the creosote so it will fall down into the stove. Anyone else heard of this or am I dreaming? I did burn one completely up Sat. morning but couldn't tell that it did a thing.

scott_vt · Feb 13, 2006

In fact I am trying to figure out some fabricated attachment with a small blower to reclaim even more of the pipe heat.

In fact years ago they did make a unit that spliced into the stove pipe, it looked like a small box with holes through it and a small blower. I never liked the idea of it, just because of what JimR just posted. You would effectively drop the temp of the smoke down to the point were greater creosote buildup would result. Not hardly worth the effort IMHO /forums/images/graemlins/grin.gif

scotty

survriggs · Feb 13, 2006

scott_vt: After posting I got to looking around and found this: Heat Reclaimer I think this is what you are talking about. I was thinking more of something a little more unobtrusive, like adding another wall around the pipe with an inlet and outlet for the blower. BUT...at the risk of lowering pipe temps I think I'll just leave well enough alone.

Egon · Feb 13, 2006

One thing is for sure, if the magnetic gauge falls off the pipe is too hot.

Egon /forums/images/graemlins/grin.gif

JimR · Feb 13, 2006

I honestly do not think you could get anymore heat out of the pipe by blocking it off. Have you tried to keep your hand over the pipe when the stove is running at 300+ degrees? /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif

Highbeam · Feb 13, 2006

The heat exchanger doesn't block it off, it actually extracts heat from the exhaust stream of the stove. Like cooling fins on an air cooled motor.

You can always add a device like that but I would say try burning a hotter fire first. Seems every house I've been in with a stove running has been plenty hot. It is when the stove goes out that the house cools off.

gunslinger101 · Feb 15, 2006

( Dave, I agree that it's always better to be cautious. I have found that if you burn hard, a horizontial flue will stay cleaner than a vertical pipe to the chimney. If I had a temperature gage and saw it rising and heard the rush from the cresote fire I would close the air off to the chimney, open a window to get the smoke out, put the fire out in the stove. Then consider the fire department and hope the fire is contained within the pipe. I am not sure the temperature gage would be very helpful at this point. By the way--been there and done that. )

If you get a fire in the stack never close air off, if you do it will back draft to your stove, open air up and splash water on the fire in the stove, the steam will kill the stack fire, don't put the fire all the way out in the stove, just splash enough to keep making steam. Clean the pipe or stack before next use.
Thats how we do it at our fire department at about 20 homes each year, unless they waited to long to call.

Boondox · Feb 15, 2006

survriggs -- That's exactly what I do. The first four feet of flue is the single walled stuff that gets hot as heck before I convert to Metalbestos pipe to pass thru the roof. I have a small cheap fan aimed at the single wall to reclaim some of that wonderful heat that would otherwise be lost.

Pete

CTyler · Feb 16, 2006

Where you have it is good.

My shop is heated with a double barrel(55gal) wood stove. Its single wall pipe up to the truss. The temp gauge is about 10 inches up off the top barrel. The air intake is pretty much wide open and the flu damper set partialy closed. Flu temps are sub 400 deg most of the time. Temps at the bottom of the truss 12' up are still low-mid 300deg.

I went to clean the pipe a few weeks ago for the first time. Basically wasted my time since its was clean. So thats two years and still clean.

The upper barrel temp at the top hot spot is ~500deg. The damper is holding the heat back from racing up the flu. Not sure if the second barrel is providing extra burning of the bad stuff or what. I was actually a bit surprised there wasn't a bunch of stuff built up since the flu temps are always near the bottom end of the "burn zone".