Crappy magnetic thermometers

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ddahlgren

Minister of Fire
Apr 18, 2011
555
SE CT
I have a lab grade probe and a couple of Rutland thermometers. I have a small fire going to take the chill off. Probe is close to 500. Rutland below it is 200 and stove top Rutland is 450. It is a lazy little fire but hot enough to not make creosote, some well seasoned maple and birch rounds so nothing serious. I woke up a bit cold at 3:30 am so the reason to start a small one. It has to make you wonder how many millions of cords of wood that have been wasted trying to keep a cheap thermometer happy.
 
? Interpreting your comment - "Probe is close to 500. Rutland below it is 200 and stove top Rutland is 450."

1. The probe is measuring internal flue temp - I assume - and the "Rutland below it is reading 200" as a surface temp on the chimney? If yes, I would expect them to be different - especially so if the Rutland is placed on double wall pipe. Even if it is single wall pipe, you are measuring two different things.

2. Stove top Rutland is 450.

Suggestion - place the two Rutlands side by side, on the stove top. And see if they match. If they do not, place them all in the the oven, and adjust the dials to match.
 
I gave my Rutland the boot (actually use it on the side, just for the heck of it), and got a Condar that is running pretty close to the IR Meter. We also lit the stove for the first time of the season this morning in my SE Corner of Ct
 
I think the real problem with any that are flat and magnetic is the fact they are flat on a round pipe. It allows room air to circulate behind them and cool the bi-metal used to measure the temp. Laying flat on a flat surface the keep the heat in. The two I have read very close to each other on the top of the stove.
 
My rutland is awful, close to 150F off at cruising temp on my stovetop compared to my IR thermometer. My Condar Inferno is within 25F in the same location on the stove.
 
I have an old condor which is within about 50 degrees up to 500 and then it can be 100 degrees or more off, the new ones I bought are worse and one of those is a rutland.
 
I have a Rutland and a Condor and they both read the same when placed next to each other on the middle of my step. (both stoves are step top) I don't use them for more than an indication anyway.

Look through the window and you'll see immediately if the stove is burning cleanly. The fire will be lazy, balls out or somewhere inbetween. There is smoke visible in the firebox or not. I've never seen a lazy fire overheat a stove. I've never seen a balls out fire that I didn't want to keep at least a little bit of an eye on. My nose and ears tell me if I needed to move more air over the stove to cool it off or put more tubs of water on it to keep it cool.

Matt
 
Teltru has a good magnetic therm that doesn't have all the colored burn zones, just a plain Jane white face with black numbers. It seems quicker to react and more accurate than my Rutlands or Condars.
 
I have a few rutland magnetics ,all are off 50-150 Deg.
 
Can you show a pic of the layout?

A few general observations:

1. For flue thermometers, it's important to be the correct height above the stoves as per the manual. That's where the manufacturer calibrates them.

2. Stove top temperatures can be quite different at different locations on the top, even a few inches away, especially when the fire is young.

3. None of these inexpensive thermometers are very accurate.

4. The consensus on the forum seems to be that Rutlands are less reliable than Condars. Don't know why.

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Is this the one, looks nice but I would like to have more range then that.
http://www.teltru.com/s-54-dual-magnet-thermometers.aspx
I can't get my phone to open that link but This is the one I have. It goes up to 750. [Hearth.com] Crappy magnetic thermometers
 
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? Interpreting your comment - "Probe is close to 500. Rutland below it is 200 and stove top Rutland is 450."

1. The probe is measuring internal flue temp - I assume - and the "Rutland below it is reading 200" as a surface temp on the chimney? If yes, I would expect them to be different - especially so if the Rutland is placed on double wall pipe. Even if it is single wall pipe, you are measuring two different things.

2. Stove top Rutland is 450.

Suggestion - place the two Rutlands side by side, on the stove top. And see if they match. If they do not, place them all in the the oven, and adjust the dials to match.

Yea you might be comparing apples to road apples.
 
500 Deg is not very usefull for the stovetop, all my stove tops cruise higher than that. I keep all my temp gauges on the stovetop. I guess its OK for the flue pipe.

Not for me, I like the one he posted a picture of that goes to 750.
 
Note that a regular surface thermometer will not be very useful for flue temps on a stovepipe. Makers of flue thermometers like Rudland and Condar know that the surface of the pipe, even single wall, will be much less than the temps inside the flue, so they have to specifically design and then calibrate them accordingly, and they have to be installed at the right height, so that they hopefully will record what the inside temp is. But it's still an indirect measure and the accuracy will be limited.

They should be fine for stovetops, though, since the surface temp is what you are concerned about.
 
Note that a regular surface thermometer will not be very useful for flue temps on a stovepipe. Makers of flue thermometers like Rudland and Condar know that the surface of the pipe, even single wall, will be much less than the temps inside the flue, so they have to specifically design and then calibrate them accordingly, and they have to be installed at the right height, so that they hopefully will record what the inside temp is. But it's still an indirect measure and the accuracy will be limited.

They should be fine for stovetops, though, since the surface temp is what you are concerned about.

Huh, they record surface temps.
 
The consensus on the forum seems to be that Rutlands are less reliable than Condars. Don't know why.
I looked at there ratings online and found this forums observations of these two brands match other consumers outside of this forum. Consumers rank the Condars as better, but neither one is set accurately form the factory.
 
My $20 HF IR heat gun seems very accurate. Much more than any of these magnetic jobs. Reads 96 pointed at my arm and other known temp objects.
 
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The only way to get an honest stove top temp is with the paint sanded and heat sink compound between the top and the sensing surface of the gauge,
 
My magnetic thermometer is gauged for single-wall pipe. Until I discovered this, I always thought it was just wildly inaccurate.
 
I have a lab grade probe and a couple of Rutland thermometers. I have a small fire going to take the chill off. Probe is close to 500. Rutland below it is 200 and stove top Rutland is 450. It is a lazy little fire but hot enough to not make creosote, some well seasoned maple and birch rounds so nothing serious. I woke up a bit cold at 3:30 am so the reason to start a small one. It has to make you wonder how many millions of cords of wood that have been wasted trying to keep a cheap thermometer happy.

On the other hand, one sometimes wonders how so many folks got along for so many years with no thermometers. Personally, I never used on until we bought our last stove. And I'll give another plus to the condar. We had some rutlands and threw them out.

Then one also has to realize that we aren't trying to keep a thermometer happy, we use the stove to warm our bodies and our homes. Let us never forget what we really want with a wood stove and that is nice heat.
 
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The only way to get an honest stove top temp is with the paint sanded and heat sink compound between the top and the sensing surface of the gauge,
Yeah, and a lot of people don't realize that IR thermometers are most accurate on flat black (non reflective) surfaces
 
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