Monitoring flue temp on an insert

[Haywire Haywood]

Is there any way to monitor flue temps on an enclosed flue like a fireplace insert w/ double or triple wall for a flue?

Ian

 

[husky455rancher]

i have no idea but id like to know aswell.

 

[Wirenut2266]

yes, but.....

Yes: You can get an type J sensor with a 3' to 20' lead for under $50 I bet. Just have tip exposed in flue or bolt on stove pipe and your good to go. Wire is high temp, so shouldn't have any problems. But.....Now you have to plug this sensor into a digital meter. Meter has to have the "temp" range on it. You may be able to pick a cheap meter off fleabay with needed range for prolly $100 or so. If really interested, let me know I will dig much deeper into options. There may be a panel meter out there as well, could look into that as well!!!

 

[Haywire Haywood]

So you'd have to drill the pipe close to a joint as you were putting it together, place the probe and then seal it back up with some kind of high temp goo?

Ian

 

[gink595]

I just use the magnetic temp gage, but instead I threw it on top of the stove rather than the flue pipe. It's a little off but you still get an idea of how hot she is.

 

[Haywire Haywood]

If things go as planned, there will be no 'top' or exposed pipe, it will be a Lennox zero clearance "fireplace". Essentially an EPA II stove camouflaged with fireplace facade. http://www.lennoxhearthproducts.com/products/overview.asp?pid=386

Ian

 

[gink595]

OH!!! I see, I see. Well Wirenut had a good idea with the thermocouple and temp gauge. I have one on my powerstroke works great, I have a extra autometer pyrometer. How cool would that be, a stove with autometer gauges:biggrinbounce2:

 

[cityevader]

Are you looking to see the actual "exhaust temp" of gas flow of inner pipe? Or the outside wall temp of double or triple wall pipe?

Makes a huge difference.

 

[Wirenut2266]

Hay: I'll assume you want temp of "chase" where triple wall pipe is running through? No just leave sensor hang loose in cavity. Those little sensors are extremely accurate. I'm talking 1-2 deg.........I do like the automotive gauge idea, could be kinda cool!

 

[Haywire Haywood]

Nope, I want the temp of the actual exhaust gasses or at least the interior pipe surface. I've read that 300-500F is ideal. Cooler and you risk excess creosote buildup, and higher is "overfiring", you waste heat up the pipe and get your stove too hot, thus shortening it's life.

I've never had a wood heater before and wanted something to make it idiot proof (or at least idiot resistant). A heat gauge would give me an indicator of when and how to adjust the intake air.

Ian

 

[chowdozer]

Nope, I want the temp of the actual exhaust gasses or at least the interior pipe surface. I've read that 300-500F is ideal. Cooler and you risk excess creosote buildup, and higher is "overfiring", you waste heat up the pipe and get your stove too hot, thus shortening it's life.

I've never had a wood heater before and wanted something to make it idiot proof (or at least idiot resistant). A heat gauge would give me an indicator of when and how to adjust the intake air.

Ian

I use these and have ordered 1000's of $ from Omega in the past 15 years. They are first rate and their tech department knows their stuff.

I don't know what type of pipe you are installing. Single wall would be easy, just weld a pipe fitting on. Double or triple wall may be a problem due to sealing around the probe on the inner pipes.

http://www.omega.com/ppt/pptsc.asp?ref=TJ36-SB_chb&Nav=tema07

It uses a compression fitting that clamps the probe in place. The compression fitting comes with it. You will need to drill a hole all the way through the pipe and weld an 1/8" pipe fitting on it. It's a 1 use probe when installed as the compression fitting crimps the probe and you can't reset the depth of the probe after you use it. It will always be the same depth.

It will be easiest to find a type K reader.

http://www.omega.com/pptst/HH11A_HH12A.html

You may have to put a ac adapter on it if you want to leave it on. I don't know if it has an auto shutoff.

PM me if you want to discuss.

 

[Haywire Haywood]

I was going to PM but thought everyone else might benefit from the discussion.

The probe looks good, I saw where you can order custom lengths so that the tip doesn't get damaged by the flue brush.. actually I worry about penetrating the inner pipe without some way of resealing it. This is going to be (I think) 2 layer pipe with insulation between. Thought about just having the probe long enough to sit against the inner pipe without penetrating.

Problem is the large multimeter type display. That sitting up on the mantle would be an eyesore. What would be ideal is a compact display with no buttons. I don't need to know averages, hi/lo, C/F/K conversion, etc... just a numerical display showing current temp, maybe 1"x2" with a connection for the cable and preferably run on a 9v or a few AA batteries.

Ian

 

[chowdozer]

I was going to PM but thought everyone else might benefit from the discussion.

The probe looks good, I saw where you can order custom lengths so that the tip doesn't get damaged by the flue brush.. actually I worry about penetrating the inner pipe without some way of resealing it. This is going to be (I think) 2 layer pipe with insulation between. Thought about just having the probe long enough to sit against the inner pipe without penetrating.

Problem is the large multimeter type display. That sitting up on the mantle would be an eyesore. What would be ideal is a compact display with no buttons. I don't need to know averages, hi/lo, C/F/K conversion, etc... just a numerical display showing current temp, maybe 1"x2" with a connection for the cable and preferably run on a 9v or a few AA batteries.

Ian

Ian, a probe in the pipe is going to be a problem for cleaning however you do it. Due to the flow in the pipe and the conduction of the pipe, the temps in the center are going to be higher than the edges. A tab mount style tc mounted on the iside of the pipe would give you the temp of the pipe, but not the temp of the actual gases and you'd still end up drilling a hole in both pipes. Doing that, you'd also have a problem getting the wire out of the inside of the pipe. A probe is the only option unless you wanted to mount a tab style outside the inner pipe and then you would only be measuring pipe temp. If you do use a tab mount tc on the outside of the inner pipe, use an all metal crimp style nut. Match materials, ie, no steel bolts/nuts on SS.

I would go with a 1/4" diameter probe and mount it as close to the stove as possible. Hopefully, the pipe entrance into the stove is a straight vertical drop so doesn't build up much creosote and doesn't need to be brushed.

About installing the probe. I don't know how the fire codes would address my suggestion, so use at your own risk.

Ok, the probe can be set to any depth, so whether you want to have 1" poking through the pipe or 3", it won't be a problem. I would recommend at least 1" because there is going to be some conduction back through the probe, into the fitting and into the pipe.

Now about the questionable part. I don't think you want to drill a hole through a 2 layer pipe and put a fitting on the outside. You leave yourself a path for creosote to enter into the insulation area and possibly cause a fire hazard at some point in the future. If I were asked to do this in an industrial enviroment, this is how I would do it. Cut about a 3" square hole in the outside pipe. Push the insulation aside. Drill a hole in the inner pipe and weld a SS 1/8" pipe fitting on it. Install the probe. Cut another piece of SS with a hole in the center for the remainder of the probe to stick out and weld over the 3" hole in the outer pipe. If you don't weld, you can use SS rivets but not sheetmetal screws as they will loosen. As I say though, I don't know how fire codes would view this (basically a patch on the outer pipe). I would make sure you have a very good welder weld the pipe fitting on too. It is not a place where you want a failed weld.

What I did on my stove, was welded a tc directly on the single wall pipe where the stove outlet is. I don't know the actual gas temp, but I know where the stove burns good and use it as a guage to set the draft. I like a pipe temp of about 300F as I have found I don't get much buildup at that temp. I usually run it up to 500F or so to burn it out.

As far as a reader, the only readers I use are handheld or panel mount. I haven't looked for a stand alone reader that would not look "out of place" on a fp mantle.

 

[Haywire Haywood]

Maybe as usual, I'm over analyzing and worrying about the little stuff too much. Looks like it's going to be at minimum a pain to install, and at worst, an actual fire hazard. If it was a free standing stove with the first section of pipe being single wall, I could just slap on one of those magnetic things.

Oh well, it was a good thought.

thanks,
Ian

 

[Wirenut2266]

Chow: That is exactly what I was thinking about. Would be kinda leary about drilling through triple wall, but that 2000deg. stove cement should fix any gas leaks. This will work really well, or :deadhorse: Good Luck!!!

 

[chowdozer]

Ian, it wouldn't be that difficult. As far as fire, I really doubt you'd have a problem if you welded the patch on the outside pipe. The only way air could get in between the pipes is through the hole in the patch and the tc probe would fill that up completely. I have had fittings welded on SS up to 1100-1200F and glowing a medium red and never had a problem. I didn't weld them myself though, I had a good welder at work.

If you want to do it, go for it. Otherwise you will have regrets and those aren't any fun.