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Are IR guns dependable for stove pipe temps?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Cudos, Oct 31, 2010.

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  1. Cudos

    Cudos Member

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    Just wondering, I bought a IR gun to check my stove pipe, surrounding wall higher up and outside stack temps. Are these dependable? Crappy tire had one on for $49.00 regular $94.00

    Cheers

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  2. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Cudos, I've played around with the idea of using one just for the heck of it. I've heard both ways; some say they are excellent and some say not. Who to believe?
  3. velvetfoot

    velvetfoot Minister of Fire

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    I too have a cheap one and I think it's pretty good-for example, agrees with thermostat, more or less. But you know, as I discovered with my oil burner, it doesn't work with a silver colored pipe. Black, yes.
  4. Battenkiller

    Battenkiller Minister of Fire

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    Why me, of course. :lol:

    Get one from a good company. I have mentioned this company several times. Everybody goes to the cheap Harbor Freight one instead, then doubts its accuracy.

    Once again, for the same $49... the LT100:

    http://www.instrumart.com/Product.aspx?ProductID=10228

    This is a great company. I got the big brother to this little baby, but this one has the same sensor and guts, just less options. I trust it and I feel it is extremely accurate. Best thing about Instrumart is they offer lifetime phone support... even for a $49 item like this. Try that with Harbor Freight. They stand by their products as well. I dropped my LT300 a few times and it developed a rattle in it. Even after telling them it was my fault, they repaired the unit for free. Only thing I paid was $5 to ship it there. Try that with Harbor Freight. They have real live engineers on tech support, and you just call them and they'll explain exactly what the deal is with your findings. I really learned how to use the thing properly by calling and asking questions. Try that with HF.

    I was told that they were very aggressive about getting these things made to the quality of a name meter like Fluke but at a cheaper price point, and they sell thousands of them to various industries each year with few complaints.

    True, you can't shoot shiny metallic objects without spending a lot more for one with adjustable emissivity (mine has it; I never use it), but for 95% of what you'll ever need to scan with it, the default setting will get you to within +/- 1-3%. That includes all parts of your stove install. Glass, cast iron, steel, soapstone, flue pipe, surfaces surrounding your stove. The contact magnetic thermometers are all over the map, and the cheap probe thermos have been demonstrated to be even worse.

    As far as flue temps, you should realize that the only truly accurate way is with a thermocouple probe and a digital thermometer. As the season goes on, the soot and fly ash inside the pipe will act as an insulator and give increasingly lower readings at the same internal temperature. My IR gun accepts K-type thermocouples, so I got one that reads up to 1300ºF for another $40. It is only 1/8" in diameter, so it just fits into one of the flue pipe screw holes. I'll periodically check the difference between the two numbers at a few different temps to allow me to know exactly what the internal flue gas temp really is at that time in the season.

    The first shot of the sequence is of my pipe about 15 minutes after a stone cold start. You can see the IR reading is 636ºF, while the probe temp is 1281º. You can also see the old Vermont Casting contact thermometer ain't too far off... reading a little over 600º vs. the more accurate surface temp as read by the gun. If you doubt my flue gases were that high, check out the shot of the probe. Even though the camera flash robbed some of the color as it looked in the darkened basement, as you can see, it's glowing red as can be.

    The second reading was taken at cruising temp. The IR says 271º, the probe says 603º.... a great flue gas temp for my stove. The stove cruises at about 650-750ºF with a flue temp this high.

    BTW, the probe is even more accurate than the gun... about +/- 1ºF over its entire range.

    Attached Files:

  5. tradergordo

    tradergordo Minister of Fire

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  6. begreen

    begreen Mooderator Staff Member

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    Water boiling at low altitude = 212F, yes. Water freezing at 32F, yes. Accurate oven temps...?, maybe, if you're lucky. The Electrolux oven we put in last year is the first one in 30+ years that has been accurate. All the rest have been off, some by as much as 60F! Our prior KitchenMaid convection oven was off by 30F before I calibrated it.
  7. corey21

    corey21 Minister of Fire

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    what about condar probe with single wall pipe.
  8. begreen

    begreen Mooderator Staff Member

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    From Condar:

    "Long-stemmed probes, inserted into a small hole in your stovepipe, give you the most precise and immediate temperature readings, for either single or double-wall stovepipe."
  9. corey21

    corey21 Minister of Fire

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    i saw last winter people said they were off is this true. i just got the model 3-39.
  10. begreen

    begreen Mooderator Staff Member

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    Yes, I recall that thread. What was uncertain was whether the thermometer itself was accurate. IIRC, a couple were not when compared to a calibrated probe.
  11. corey21

    corey21 Minister of Fire

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    i think what i will do is put the rutland beside the probe for a while. but should i be concerned about those threads.
  12. begreen

    begreen Mooderator Staff Member

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    It is just data. No need for serious concern unless your other senses start telling you something wrong. If you see something glowing dull red, or smell something very hot, or hear a roar coming from the flue, that is the time to be concerned. But all of this is very unlikely with a properly installed flue and stove system burning dry wood as per manufacturer's directions.
  13. corey21

    corey21 Minister of Fire

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    Thank you BeGreen sorry about hijacking the thread.
  14. begreen

    begreen Mooderator Staff Member

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    No problem. How has that Magnolia been running for you so far?
  15. corey21

    corey21 Minister of Fire

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    Been doing great so far. Just had some morning fires so far as temps outside have been mild 32-38 when i used it so far. my house holds in heat very well the Mag has already had my living room to 84. oh the other day the burn tubes light off it freaked me out.
  16. ozarkjeep

    ozarkjeep New Member

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    yep, had a $29 HF temp gun for a few years now, it will show different temps for boiling water with as little as a couple of hundred feet difference in altitude.

    they are plenty accurate for what most folks use them for!




  17. DanCorcoran

    DanCorcoran Minister of Fire

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    Yeah, I'm not sure what Harbor Freight shows as a "list" price for their IR gun, but it is very often on sale for $25.99 to $29.99 in the store. I got mine for $29 and it works fine and is as accurate as I need for making sure my walls aren't going to spontaneously combust.
  18. tradergordo

    tradergordo Minister of Fire

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