Telescoping pipe and flue temp monitoing

First, thank you to all who have got me this far. I last used wood as my only source of heating in an old drafty farmhouse in 1985. Two years ago I bought a new Hearthstone Heritage, and it has taken me this long to get it hooked up--it had to take it's place in line with the kitchen/living room rebuild. This is not the same farmhouse I had in 85, but it started in as bad a shape--now it's insulated well and from what I can tell thus far the Heritage is a good match. The thank you is for all the great advice I received on the chimney install (Excel) and the hearth build, along with a host of other miscellaneous questions.

The current question is about monitoring temperatures. I bought 2 magnetic stove top temp gauges, a Rutland and an Inferno. They both read about the same on the center of the top of the Heritage so I presume they are fairly accurate. I know they are of no real value on my stove pipe. I have only been running the stove 2 days now, and did 3 break-in fires yesterday, first--up to 100, then 200, then 300 degrees. Now I am cautiously burning in the 400-440 range, per the stove top thermometers. But I have no idea what my stove pipe temp is.

I really don't even know what you would classify my stove pipe as. It is also by Excel, telescoping, with 2 walls for both the top and bottom halves--bottom piece telescopes in between the 2 walls of the upper piece. Considering the bottom of each pipe is open, I don't know if that is technically considered double wall or single wall.

I was planning on seeing how the stove operated and then getting a probe thermometer. After reading various threads, including the very interesting one with many thoughtful replies including descriptions of experimentation done with Condar and other probe thermometers, I am wondering if there are other ways to go. I don't understand if the thermocouple route is appropriate with my application, or if it is very similar to using a probe thermometer.

My set up is straight up stove pipe and chimney, no bends or elbows. I have 4 and a half feet of the telescoping pipe, 10 feet (if I remember correctly) of the Excel insulated class A chimney pipe, extending about 4' above the roof. The overlap in the telescoping pipe has the bottom of the top section 16" above the flue collar or 18" above the stove top.

I have also considered getting an infared meter to use to understand stove top temps, as that soapstone takes a long time to change with start-ups. My thinking there is I could aim it at the black cast part on the stove top next to the bottom of the flue collar and get a quicker idea of what is happening at start up and cool down.

And again thanks for all the help thus far. It was 18 below this morning, is supposed to be 25 to 30 below tonight, and the stove at the low 400s is keeping the house in the lower 70s. Your advice thus far is helping us stay warm and toasty here in Wisconsin.

blueguy said:

Your double wall is most likely UltraBlack and the slip section you're speaking about is just like mine - it's double wall. I have a probe thermometer in my slip section 18" up from the stove collar and it works well for my needs....

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Yes, I checked some paperwork and I do have UltraBlack. 18"up will put me thru 4 layers of pipe--is that what you had to do?

simple.serf said:

My telescoping pipe is a double wall. There is one spot that runs the hottest, and I use this spot, along with the stove top temp and visually monitoring the fire, to get an idea of what is going on.We aim for 250 at this spot during normal operation, with 300 being too hot. the rest of the ipe is usually around 150 during this check.The temp here is being checked with a IR gun. I have a "homesaver" gauge on the stovetop, just in front of the pipe outlet, and it normally reads about 400 (with an IR gun, I usually get about 600 at the hottest spot and about 400 where the gauge is).

Since we have been burning with this stove (3 years now) the pipe always looks good when taken apart for cleaning and we do not have issues with excessive creosote.

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Sounds like you use the 150, 250, 300 more numbers as benchmarks rather than trying to know exact flue temperatures, and then compare to real life--checking for the creosote formation. I like that, that's good common sense. 2 questions. 1. Is that hottest spot down close to the stove top?--that's what I find on my telescoping pipe. 2. I don't know if you have a straight shot up to the cap, but it sounds like you take apart your pipe for cleaning. As far as I can see, that is what I will have to do also, taking it apart in the house, sliding the bottom section up a little, putting a container on top of the stove, and using the brush from above on the roof. On my old pre-EPA stove, I also had a straight up shot to the cap--but could just put a container within the stove and catch most of it, and vacuum out what didn't fall into the container. That was nice, but then again, it made a lot of creosote and I was cleaning fairly often.

blueguy said:

My flue probe is at 18" above the stove top, which is 6" above where the bottom part of the 12" slip ends so it's only through two layers

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Dairyman and Blueguy; Thanks. I used 36" pieces of telescoping pipe--the suggestion of the dealer; they came 2 in a box. With my set-up, if I go above the overlap, that would put me 36" above the collar, 38" above the stove top. Considering the Condar probes are advised to go 18" up, would that just make everything skewed with the readings? I'd be about twice as high as I should be. I suppose I could take it apart and scrap the lower half and put in a new bottom 1/2...

Highbeam said:

You need a condar probe meter. Easy to install, cheap, and accurate for your uses. The heritage really scorches chimneys, it sends a lot of heat up the flue so you'll want to monitor flue temps and there is no way to do it with double wall except by using a probe meter designed for it.

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I have heard that the heritage does send a lot of heat up the chimney. I suppose the good part is less creosote. But when you say scorch, what do you mean--maybe cause physical harm? Shorten the life of the chimney? Get close to exceeding the fire rating? Or wasting heat during parts of the burning cycle? Not at all questioning your thoughts, just looking for clarification.
Thanks

Highbeam said:

The heritage sends especially hot flue gasses up the stack during warm up time. I regularly would run that probe meter up to 1250 before the stone was hot to the touch. I only realized the flue was so hot after I began monitoring so who knows how hot it had gotten before that. With double wall you won't even see the inner wall glow. Yes, you will easily exceed the flue's fire rating if you're not careful.

Yes, the stack stays clean. In addition to high early flue temps, the heritage was designed to dump vast amounts of heat into the flue during the entire burn cycle. Expect to see 800 degree temps when the damper is shut off. That's pretty dang high for a flue system rated at 1000 continuous. Nice and clean flue, good drafter. This isn't a non-cat thing, plenty of non-cats are designed to run cooler flue temps.

I am not certain if chimney life is lessened due to hot temps within the range allowed by the maker but I would expect shorter life when those max temps are exceeded knowingly or not. It's so easy with that stove.

The extra high flue heat being sent up the stack is certainly a sign of an inefficient stove. That heat could have been kept in your home and saved you wood.

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Thanks for the reply. Your history with this stove is helpful to me. I have been hesitant to go the probe route after reading some lengthy threads regarding the accuracy of the Condar probes, or maybe more correctly, the accuracy of the way they are sometimes used. It seems to me that the probe is likely still the most appropriate way to monitor flue temps.

We have been having minus 30 up here in northern Wisconsin--the high today was minus 27. Per stove top thermometer, I run at about 370--430 and am comfortable. Using an infared gun I picked up today, I have shot my pipe at several spots. Right at the little bit of the single wall I can get at that is part of the flue adapter (stove cast flue collar below it, telescoping pipe above it) I get around 500. Using what I guess is the rough rule of thumb of add 50% to that for the flue gas temp, and I would have about 750. I also have shot at the top of the telescoping pipe. I did not put the trim collar on, so what is up there is 3 walls in more or less direct contact with each other--one would be the wall of the flue extender sticking down from the support box, and the other two walls would be the 2 walls of the telescoping pipe coming together for the top 3/4" or so. Per the infared gun, that has been considerably less than the 500 at the bottom end. These are max temperatures I have had thus far in my very very limited experience with this stove.

I agree that I need a better way of knowing what is going on in there. Probe is likely my next step. I'm still wondering if the thermocouple several forum members write about has something additional to offer. I really don't know diddle about thermocouples, or what benefits they might add.

Do you think there is anything I would be able to see when I clean or inspect the pipe that would let me know if it has gotten to hot?

And I hope to never see that little bit of single wall at the stove adapter glow red.
Thanks

Dairyman said:

I believe that mine is at 36". I

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Thanks. Good to know that is an option if I don't want to go thru 4 layers. And if I change the lengths of the pipe, which I doubt, I certainly don't feel like doing it during the heating season. I guess what you really want to know is the flue temp, more or less in relation to the class A pipe which is still above either an 18 inch or a 36 inch high placement of the probe.

Highbeam said:

Just get the condar probe and don't overthink it. We members are stove fanatics and we use condar probes because that is the way to measure flue temps of a double wall pipe.

Anything else, even an IR gun, is just wasting time. Sticking a thermocouple in your flue and running a wire to some computer display is something you would do in a lab to get the ultimate accuracy. That is not what you want in your living room.

The more common rule of thumb is to double exterior temps for interior temps on single wall. That's what I do on my single wall, especially when trying to prevent overfire as it is a more conservative factor.

Your flue system is stainless steel, even the interior of the double wall section. That material can handle some very high temperatures. I suspect that your double wall interior pipe (the hottest part) is more able to tolerate overfire than the class A.

The times when the heritage flue temps were the highest was when I was first warming up the cold stove with a very open throttle. Stone stove doesn't feel hot and the double wall pipe doesn't feel hot so you keep letting it rip.

Just order the condar. You're a perfect candidate. You'll love being able to monitor your stove operation from the couch. After installing that flue probe meter I hardly ever monitored the stove top temp.

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Your advice--don't over think it--I basically need that in every phase of my life. But you could probably tell that from my posts.
And you're comment that members here are fanatics--I'm glad the folks on this forum are really into stoves, safety, heat, and everything related. That provides for lots of information and good back and forth on subject matter. And always cordial as far as I can tell. And often with some good humor.
So I will get the Condar. It will give me a good idea of what flue temps are under differing conditions and phases of the burning cycle. In the end, my guess is I will be using the way the fire looks, how clean the glass is staying, what's coming out of the chimney, and what the pipe looks like at cleaning time to adjust my user techniques.
Thanks again.