Flue Temp

[Berner]

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?

 

[Grisu]

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.

 

[begreen]

Interesting 45 deg tee there. I like it. Where was that from?

 

[Berner]

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.

 

[begreen]

Well done. Do you get a valid reading at the top of the 45? That is probably where I would aim the IR.

 

[Berner]

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?

 

[begreen]

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.

 

[Berner]

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?

 

[begreen]

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.

 

[Berner]

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?

 

[Grisu]

Probe thermometer if you don't mind drilling a hole in your nice T.

 

[Berner]

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?

 

[Berner]

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.

 

[begreen]

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.