Flue Temp

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Berner

Feeling the Heat
Feb 1, 2012
388
Eastern, MA
I read a lot about flue temps on this website. I have a PH rear exit to a T connection to a flex king pro liner. I have the standard thermometer that woodstock supplies you that I put in the recommended spot, back center ontop of the "Progress" label.

My question is how do I get flue temps for this setup? I have an IR gun but the temps vary a lot depending on where on the T they are taken. What do you guys think?

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Reflective surfaces are hard to get a good reading on with an IR thermometer. Maybe try putting some black stove paint on some part of the upper T and measure that one. Check also the distance-to-spot ratio of your IR thermometer. If you are reading from 2 ft away due to the hot stove you may also measure a good part of the back wall.

A magnetic flue thermometer on the T may work better if you are really interested in measuring your flue temps.
 
Interesting 45 deg tee there. I like it. Where was that from?
 
Interesting 45 deg tee there. I like it. Where was that from?

It was a custom job from the guys at rockford chimney. Very happy with the way it came out. Much better than the adjustable elbow that used to be in there.
 
Well done. Do you get a valid reading at the top of the 45? That is probably where I would aim the IR.
 
Reflective surfaces are hard to get a good reading on with an IR thermometer. Maybe try putting some black stove paint on some part of the upper T and measure that one. Check also the distance-to-spot ratio of your IR thermometer. If you are reading from 2 ft away due to the hot stove you may also measure a good part of the back wall.

A magnetic flue thermometer on the T may work better if you are really interested in measuring your flue temps.

Good call on using the IR gun at different distances. In general it is a cool toy but very hard to get consistent results.

I think the magnetic thermometer is the way to go. However all the magnetic thermometers I have found are flat circles. Flat circular objects don't mount well on a round T. Does anyone know of any flat magnetic thermometers?
 
Not sure if a magnetic thermometer will stick to the stainless tee. It will depend on the stainless. Test it with a magnet first. If the stainless is magnetic a small round surface flue thermometer will work. Single wall flue pipe is the same round diameter.
 
Well done. Do you get a valid reading at the top of the 45? That is probably where I would aim the IR.

I will check out the specifics tomorrow but from what I recall the front of the pipe was about 75 degrees hotter than the back of the pipe. Maybe I should take the average of the two?
 
The front will be hotter. It's the upper surface that the flue gases will contact as they make the turn up the flue. This will be a surface temp. The flue gas temp inside will probably be 50% higher.
 
Not sure if a magnetic thermometer will stick to the stainless tee. It will depend on the stainless. Test it with a magnet first. If the stainless is magnetic a small round surface flue thermometer will work. Single wall flue pipe is the same round diameter.

I tested the T and it is not magnetic. Are there other options that could work for this setup?
 
Probe thermometer if you don't mind drilling a hole in your nice T.
 
The front will be hotter. It's the upper surface that the flue gases will contact as they make the turn up the flue. This will be a surface temp. The flue gas temp inside will probably be 50% higher.

I tested the T with my IR gun. It varies plus or minus about 100 degrees depending on which part of T I hit. The front top at the stove collar is the highest and the back of the clean out is the lowest. I chose the top, front, center right before the flex liner as a control point and it was about half the stove top thermometer. Does this seem right?
 
Probe thermometer if you don't mind drilling a hole in your nice T.

Forgive me for my newbie question but that is something that I would leave in permanently correct? Do they ever have problems wiggling loose? I would imagine a probe that has a 3inch long probe would loosen over time.
 
I tested the T with my IR gun. It varies plus or minus about 100 degrees depending on which part of T I hit. The front top at the stove collar is the highest and the back of the clean out is the lowest. I chose the top, front, center right before the flex liner as a control point and it was about half the stove top thermometer. Does this seem right?
That's where I would read from. No probe needed, the tee is single wall.
 
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