Thermocouple probe Sensors to measure furnace temps

Englander

Member
Dec 23, 2012
13
Well its been about 8 years and my old Englander 8-3500 wood and coal furnace is still serving me well. I would like to add some digital Type K Thermocouple probe Sensors and wanted to know if I can install one in the flue and then one in the jacket or next to the HW Thermostat ? I have added a picture of my flue /stack ( does not look as shiny as that any more) and a example thermocouple but wanted to see the spots that I should be checking for temperatures, I would love to get a warming if my flue was getting too hot and then to also monitor the temperature of the outbound air thats going in to my duct work.

 

andym

Feeling the Heat
Feb 6, 2020
371
Hicksville, Ohio
You can install into the flue. I don't have experience with double wall pipe though. You wI'll want a probe that is long enough to reach the center of the flue for realistic and accurate temps. Some probes are adjustable for depth.
 

andym

Feeling the Heat
Feb 6, 2020
371
Hicksville, Ohio
Just looked at the pic again....maybe that is just single wall afterall?
For a plenum temp again you will ideally have a probe long enough to reach the center of the airstream.
What are you connecting the probes to for a readout?
 

Gearhead660

Minister of Fire
Dec 20, 2018
623
Southern WI
Check out the Auber AT200. It comes with a probe and has an alarm.
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,051
NE Ohio
Here's what I have...1 probe in flue, 1 in the plenum. Batteries last a whole season (+) if anyone is wondering...
Amazon product
 
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trx250r87

Burning Hunk
Nov 30, 2012
158
NE Wisconsin
Well its been about 8 years and my old Englander 8-3500 wood and coal furnace is still serving me well. I would like to add some digital Type K Thermocouple probe Sensors and wanted to know if I can install one in the flue and then one in the jacket or next to the HW Thermostat ? I have added a picture of my flue /stack ( does not look as shiny as that any more) and a example thermocouple but wanted to see the spots that I should be checking for temperatures, I would love to get a warming if my flue was getting too hot and then to also monitor the temperature of the outbound air thats going in to my duct work.

This looks very similar to the probes that shipped with the Heat Commander. I was able to install in my double wall black pipe by drilling a hole and inserting the nut between the 2 layers of metal pipe.

Eric
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,051
NE Ohio
This looks very similar to the probes that shipped with the Heat Commander. I was able to install in my double wall black pipe by drilling a hole and inserting the nut between the 2 layers of metal pipe.
So the TC's aren't built in to the firebox on the HC?
I was wondering where they are located...
 

trx250r87

Burning Hunk
Nov 30, 2012
158
NE Wisconsin
So the TC's aren't built in to the firebox on the HC?
I was wondering where they are located...
Yes but there are also 2 like @Englander mentioned above that came with the Heat Commander that are used in the flue and plenum. These might only ship with those furnaces that are a part of their connected program.

Eric
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,051
NE Ohio
These might only ship with those furnaces that are a part of their connected program.
I bet you are right.
So where is the TC in the firebox located?
 

Englander

Member
Dec 23, 2012
13
Thanks for all the replies and information the AT200CHIM looks pretty nice and cost effective , I am looking to put these sensors in to raspberry pie and add more smarts to the furnace and also be able to graphic the temps.

I guess my chimney is not a true double walled flue and its more of a pipe in a pipe black pipe in the center and then another pipe over it. But near the bottom can gain access to the black pipe. I read that some people use Rivnut Inserts in there chimney if the probe comes with a threaded insert then you just screw it in to the Rivnut.

What kind of temperatures could I expect in the chimney ? as I need to make sure the probe I use wont max out or burn out
 

andym

Feeling the Heat
Feb 6, 2020
371
Hicksville, Ohio
Thanks for all the replies and information the AT200CHIM looks pretty nice and cost effective , I am looking to put these sensors in to raspberry pie and add more smarts to the furnace and also be able to graphic the temps.

I guess my chimney is not a true double walled flue and its more of a pipe in a pipe black pipe in the center and then another pipe over it. But near the bottom can gain access to the black pipe. I read that some people use Rivnut Inserts in there chimney if the probe comes with a threaded insert then you just screw it in to the Rivnut.

What kind of temperatures could I expect in the chimney ? as I need to make sure the probe I use wont max out or burn out
Hopefully less than 800°F at all times. I think a K type is rated for more than that.
 

Englander

Member
Dec 23, 2012
13
Hopefully less than 800°F at all times. I think a K type is rated for more than that.
I think some of them are but I was finding alot with max temps of 500F, What do you think the max temp might be in the jacket around the firebox ?
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,051
NE Ohio
You have to pay attention...some sensors can read to xxx degrees, but can take more without damage...like read to 5-600, but OK to 750...have to watch if they are listing temps in C or F too.
Air temps could be 100-150* F...maybe a little more sometimes? (especially during power fail)
Flue temps...3-400* commonly...could be 5-600* if air is way open after loading...
 

trx250r87

Burning Hunk
Nov 30, 2012
158
NE Wisconsin
My wood furnace plenum temp, measured at the top of the plenum gets to @200 degrees F before the high limit kicks in and fan turns on. I'm not sure what the air jacket temperature is.

Eric
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,051
NE Ohio
My wood furnace plenum temp, measured at the top of the plenum gets to @200 degrees F before the high limit kicks in and fan turns on. I'm not sure what the air jacket temperature is.

Eric
Wow, really?! It doesn't kick on until 200? That's awful high...
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,051
NE Ohio
It probably pushes the heat out pretty good without the blower. I remember one of the SBI guys mentioning that in one of the other threads recently.
That's all dependent on your duct system...if you have some rise on your runs, etc
 
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trx250r87

Burning Hunk
Nov 30, 2012
158
NE Wisconsin
Wow, really?! It doesn't kick on until 200? That's awful high...
I don't know what SBI's #'s are but my cheap meat thermometer style thermometer usually shows 200 degrees when the high limit kicks the fan on. This is ONLY when the wall thermostat is satisfied.

Eric
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,051
NE Ohio

sloeffle

Minister of Fire
Mar 1, 2012
776
Central Ohio
Thanks for all the replies and information the AT200CHIM looks pretty nice and cost effective , I am looking to put these sensors in to raspberry pie and add more smarts to the furnace and also be able to graphic the temps.
Personally, I'd pass on using a Raspberry Pi to control something that could possibly burn my house down. I think it would be okay to take temps etc but I'd be a little hesitant on using one to control my furnace since it is a micro computer vs a dedicated PLC or a microcontroller ( Arduino ). From my personal experience in working in IT over the last 20 years, computers like to crash, run out of memory, hit a software bug at the most inopportune times. I also wouldn't trust using a scripting language such as python, Perl, or ruby to run the automation. Scripting interpreters can be buggy also. If you do go the Raspberry Pi route I'd write the code in C, C++, or Go ( compiled code ) with lots of error checking ( try catch ), and alerting.
 
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andym

Feeling the Heat
Feb 6, 2020
371
Hicksville, Ohio
Personally, I'd pass on using a Raspberry Pi to control something that could possibly burn my house down. I think it would be okay to take temps etc but I'd be a little hesitant on using one to control my furnace since it is a micro computer vs a dedicated PLC or a microcontroller ( Arduino ). From my personal experience in working in IT over the last 20 years, computers like to crash, run out of memory, hit a software bug at the most inopportune times. I also wouldn't trust using a scripting language such as python, Perl, or ruby to run the automation. Scripting interpreters can be buggy also. If you do go the Raspberry Pi route I'd write the code in C, C++, or Go ( compiled code ) with lots of error checking ( try catch ), and alerting.
I love raspberry pie! My wife is making one right now actually! Mmmm. Lol!
I didn't understand a word of the rest though. ;?:oops:
 

lotawood

Member
Dec 11, 2011
78
montana
I use a Mypin PID controller. It came with sensor like what is in post #1.
I wanted a higher quality k-type thermocouple. So I got something higher quality from amazon or ebay.
A $10 k-type thermocouple. Having trouble with a link.
Lots of choices with length and upper temperature rating. I get the over 2000° ones.
I use it on a wood boiler with high temperatures in the secondary combustion chamber. These might last a couple of years there. I consider it a consumable part. I could spend more on it to get it to last longer with some ceramic shields.

That PID controller has some alarm options that I'm sure most of the others do. I use indicator lights with the alarm options. Maybe you want a buzzer or a bell for over temp.
 
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