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Installing Multiple Thermocouples

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  • Installing Multiple Thermocouples

    I am about to pour my tabletop and am interested in installing some thermocouples in my oven. I wanted to get the fourm?s opinion on measuring multiple points within the oven. I am considering installing 8 or 10 thermocouples with the idea of mapping the heating of the oven. I think it would be interesting to see in real-time how the oven comes up to temperature, and when the bricks become ?soaked?. I have not yet worked out the details but it should be possible to feed all the thermocouples into a multiplexer and run that to something like an Arduino. I ideally would like to have a color LCD which would show the hot and cold spots of the oven.

    I realize running 10 thermocouples into the oven will not be easy, which is why I wanted to start a conversation about it. Over time I can foresee some of the thermocouples dying and would need to replace them. Is there some way anyone has found to help facilitate this? I am thinking I would have a few under the floor, and at least one on the cooking surface. That would also be true for the ceiling of the oven, but perhaps this is too difficult. Let me know what you think.

    Thanks for any input.

  • #2
    Re: Installing Multiple Thermocouples

    My $0.02 - it's a lot of work and expense for not a lot of value in return. Having a wood-fired oven is probably enough geek cred all by itself. I wouldn't overthink it. Probably better to think about 2 or 3 that are well placed and that you can actually get to if you think that you might need to replace them (have no idea if this is the case, though the ones I have used seem pretty cheaply made).

    But it's just an opinion.
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    • #3
      Re: Installing Multiple Thermocouples

      Do a search in the forum for thermocouples. I have seen quite a few threads here where they've been installed/used/evaluated. I remember some folks created and posted graphs with exactly the kind of temp/time/depth info/data you're talking about. I also seem to recall that in general, once you get a feel for how your oven performs...the thermocouples are considered by many of us as overkill or at least an unnecessary expense (and as noted above by Deejayoh, 2-3 of them well placed would probably be plenty-especially with the geek cred of just having a wfo). Again, I know there is quite a bit of info in the forum from people who have installed them & used them, so take some time and search 'em out.

      I created data graphs (one attached below) for my oven simply using the IR gun and Excel...once your oven has been fired and the temp equalized for an hour or two, the assumption is that the firebrick temperatures are fairly consistent throughout. Cool down is gradual as the bricks bleed heat back into the oven air (especially with today's recommended WFO insulation). Once I established my oven's characteristics, I now just gun the hearth temp prior to bread/whatever going in so I can adjust my baking time as needed.
      Attached Files
      Last edited by SableSprings; 11-05-2014, 03:40 PM.
      Mike Stansbury - The Traveling Loafer
      Roseburg, Oregon

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      • #4
        Re: Installing Multiple Thermocouples

        I installed three thermocouples on my build. My oven is a barrel vault. The hearth is 36 inches wide and 40 inches deep. I have one embedded in the middle of the hearth a half inch into the brick and two inches below the hot face. I have one in the top-dead center of the vault between the brick and insulating blanket as far from the hot face as possible. I have the last one six inches from the rear of the oven, also at the top of the vault, but this one is embedded in the brick one inch from the hot face.

        I think they are completely unneeded for cooking pizza. If you want just a few pizzas, build a forty-five minute heating fire, get the surface to eight hundred and start cooking. If you plan to do a bunch (say thirty or forty) do a big three hour burn and you'll be good to go. All you need is a an IR gun.

        I do find thermocouples very useful for baking multiple large batches of bread though. I can track the degree of heat saturation with great accuracy and that allows me to predict and manipulate the temp profile more accurately than I could otherwise, despite the fact that I have used my oven a lot over the past two and a half years.

        Using the oven a lot a allows you to predict things without using temp probes, but I frequently will light a fire the night before a bread bake and let it burn out over night with the door partially open. Then I do a small to medium fire in the morning during my bulk ferment in order to re-heat the surface of the masonry and partially re-charge the deeper layers.

        The over night fire means you're not there to tend and watch the fire and have no real idea when it went out....and it means that the surface of the bricks are invariably substantially cooler in the morning than the deep masonry levels due to the fact cool night air has come in through the open door after the fire went out. Under these circumstances it would be very difficult to know the temps of the interior of the masonry without thermocouples.

        I typically do very large bakes on a single firing. I will sometimes do three separate bakes of 15 or 16 loaves in each bake. Despite the barrel vault shape, my oven is a low mass design (for the sake of quicker heating) but is very well insulated. My hearth only 2.5 inches thick. and I have no cladding on it whatsoever. I know that (for optimum performance and the most bakes) when my bread goes in the oven I want the surface bricks to be around 550 and I want the deepest layer of masonry to be around 625. That is my oven's sweet spot for bread. I can't reliably do that profile without the thermocouples.

        As the surface cools down during the bake from all the steam being released from the dough, the higher temps deep inside the brick keeps the surface well charged and maintains temps. That profile allows me to easily do three large, consecutive bakes. After finishing the third bake and letting the oven rest thirty minutes with the door on, the oven will generally be above 450 range when I'm all done. That puts me at 350 the next day and 250 the day after.

        So if you're doing bread, they make a lot of sense in my opinion. I do think ten might be overkill though....but it's your oven so put as many as you want in.

        Last edited by WJW; 11-05-2014, 10:56 PM.


        • #5
          Re: Installing Multiple Thermocouples

          Kbartman has 11 thermocouples in his oven. I would take a look at his oven build.

          I have 4 remote dial thermometers installed in my oven. Two centered in the hearth and 2 about halfway up the side of the dome. In both locations one is on the outer surface and the other is about 1/2" from the cooking surface. I also just picked up an IR temperature gun because I like toys!

          Link to my oven build thread:
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          • #6
            Re: Installing Multiple Thermocouples

            Thanks for the replies guys. I will be baking bread so it seems useful to have some data pouring out of the oven. Maybe 10 or so is overkill, but I am a pretty geeky guy. Ill keep you updated.