how hot can exhaust get?

[OH_Varmntr]

OMG.....OMG.....OMG!!!!!

What the hell are you guys doing?????
If I am wrong..my bad ,but it looks like you are taking external pipe temps?

If so add 400-500 degrees. To make an accurate measurement you must take it from the center of the flue.

...to add you are advocating over firing...most warranties are now void due to that advice.

Do you have any actual data to back this up? Just curious.

I'd like to take a probe type t/c and hook it up to mine and check the center of the flue temps. See how far off it actually is, but if you actually have data to back up your claims then it would save me the trouble.

 

[CrappieKeith]

Data...water freezes at 32 degrees Fahrenheit and boils at 212 degrees f.

Flue gases condense at 230 degrees f.

I have shot multiple times a single wall flue pipe with a laser temp gauge.
With a 400-450 flue gas temp inside the pipe the outside of the pipe ran around 110 degrees. The 90's and 45's ran a touch hotter by a few degrees with the flue gases bouncing off of the metal being redirected.

So the point I am making is this. Taking external temps do not give you real flue gas temperatures.
If you are getting a 400 degree external temp the flue gases are much hotter inside the pipe.

Flue gases can be hot in the center of the flue ,but in the case of cold masonry flues we see smoke peeling off of the main stream and doing a U-turn following the cold walls back down until they become so cool that they liquify...all in the same flue/chimney.

Be careful when doing your own testing. I recently had a customer do his own tests. He used a regular thermometer. It was not rated very high...the outside of the pipe was 250 and when he went to read the inside his mercury exploded out of the glass thermometer.

 

[OH_Varmntr]

Data...water freezes at 32 degrees Fahrenheit and boils at 212 degrees f.

Flue gases condense at 230 degrees f.

I have shot multiple times a single wall flue pipe with a laser temp gauge.
With a 400-450 flue gas temp inside the pipe the outside of the pipe ran around 110 degrees. The 90's and 45's ran a touch hotter by a few degrees with the flue gases bouncing off of the metal being redirected.

So the point I am making is this. Taking external temps do not give you real flue gas temperatures.
If you are getting a 400 degree external temp the flue gases are much hotter inside the pipe.

Flue gases can be hot in the center of the flue ,but in the case of cold masonry flues we see smoke peeling off of the main stream and doing a U-turn following the cold walls back down until they become so cool that they liquify...all in the same flue/chimney.

Be careful when doing your own testing. I recently had a customer do his own tests. He used a regular thermometer. It was not rated very high...the outside of the pipe was 250 and when he went to read the inside his mercury exploded out of the glass thermometer.

That's unfortunate, I hope your customer was not harmed.

What was the draft measured in the flue when you were taking readings? A higher draft is moving flue gasses at a higher rate of speed inside the flue, therefore not transferring as much heat to the pipe and vise versa, correct?

 

[CrappieKeith]

That's unfortunate, I hope your customer was not harmed.

What was the draft measured in the flue when you were taking readings? A higher draft is moving flue gasses at a higher rate of speed inside the flue, therefore not transferring as much heat to the pipe and vise versa, correct?

We were trying to figure that out...he did not have a manometer. I know with our furnaces a 400-450 flue gas temp he should have been at .03" of w.c. which is what we call for.He said he had a thermometer...I assumed it was a metal one....last time I assume that.

No ...a faster flue gas speed will cause the firing rate temp to increase which heat is what drives the natural draft process.So in effect more heat or hotter heat will be vented with faster draft speeds.
The not transferring part is true in the furnace or stove. The heat exchanger can exchange heat only so fast....if you move a draft to fast it can cause the unit to become less efficient...although you will achieve a cleaner...less partuculated flue gas....but efficiency can be some what gained with more thermal mass and more heat exchanger surface area....but only to apoint.
Like anything there's only so much you'll be able to achieve...when you add in size...price point...I mean what market share is there for physically large appliance that cost 10 grand that go in a house. Sure...the idea can be done,but who's gonna buy it ...enough that it's worth investing in.

I make a great hair jig...deadly as all get out....the big manufactures tell me it's too small for main stream fishermen. They do not dispute how well it works....but they will not make it...in truth it is too hard to mass produce.

 

[OH_Varmntr]

Gotcha. I'd still like to install a probe type t/c and measure the difference on my furnace. Seems like there are a few variables that I'd like to play around with to see their affects. I've got access to plenty of probe t/c's.

 

[kstill361]

I have an internal probe on mine, I thought about the alarm only for the purpose of the bottom door accidentaly left open which i think is what ended the life of my old furnace. My wife was new at running a wood furnace, and I did not realize she was starting a fire and going back upstairs to get ready for work thinking "I will just go back in a few minutes, I have time to put on my eyeliner" Wrong!! I was on the phone with her one morning when she did this so im sure it happened more than once.

My Energy King calls for .06" of w.c. which will run my internal flu temp around 800F-900F
My fan limit switch is set at 175F . This cycles my internal flu temp 400F-900F

I use a manometer to check the draft daily

 

[kstill361]

The above temps are from burning Black Locust, it varies depending on the type of wood

 

[aaronmach1]

what is w.c.

 

[CrappieKeith]

water column...you need a manometer to measure it.Draft speeds are measured in w.c.".

 

[aaronmach1]

so to some it all up, if your using an oustide the pipe thermo then your burn range is "not" 300f-600F? what should my burn range be for a outside magnetic thermo then?
If this is true then the rutland company shouldnt be selling them thermo's. It could burn somones house up.