Author Topic: Thermometer/temp probe placement  (Read 1480 times)

Offline domanah

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Thermometer/temp probe placement
« on: March 05, 2018, 11:42:22 AM »
Hello, I use an electric urn and was wondering where is the best position for my STC1000 temp probe to control the mash temperature. Regards, domanah

Offline durrettd

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Re: Thermometer/temp probe placement
« Reply #1 on: March 05, 2018, 07:18:06 PM »
Build a thermowell and hang it in the wort/mash:

Buy a length of copper tube large enough to slide the sensor into and long enough to reach from the rim of the BK into the wort and a small roll of lead-free solder.  Pinch one end of the copper flat and drop a length of solder into the tube. heat the bottom of the tube - and the piece of solder until you see a drop of silver through the flattened bottom. Remove the torch and let the copper cool.

Hang the copper - with sensor inserted fully - in the mash/wort.

If you install the sensor thermowell through the side of the BK, it will interfere with the bag of gain.

Offline GigaFemto

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Re: Thermometer/temp probe placement
« Reply #2 on: March 05, 2018, 08:09:25 PM »
There is no correct answer, although durettd is close. Many kettles (including mine) have threaded ports on the side where you can insert your thermometer. The mash can stratify, with higher temperature at the top than the bottom, and when you stir it up there will be a big change in reading. Also, there is a delay from when the controller applies power to the heater (near the bottom) and when the temperature sensor (several inches higher) responds, and this can cause some control loops to oscillate. Using a vertical copper tube, which has excellent thermal conductivity, should help your sensor to average the temperature from top to bottom. There can still be issues with the horizontal placement, and the shape and placement of your heater coil have a major impact there. Unless your kettle is very well insulated, the outside edges will be a bit cooler than the center. I have a Blichmann boil coil, which is near the outside edge of the kettle and helps counteract that. If you have a heater that goes straight across the center then that can exaggerate the center-to-edge difference by heating the middle more than the edges.

Jut try something and see how it works. What happens when you give your mash a good stir? That will tell you how well your sensor is indicating the overall temperature of the mash. Then, even if things are not perfect, don't worry too much about it. RDWHAHB

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Offline domanah

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Re: Thermometer/temp probe placement
« Reply #3 on: March 08, 2018, 01:39:37 AM »
Hello, thanks for the replies. I noticed that if I stir the mash slightly the temp drops by about 4 degrees C. How deep should the thermow well go into the wort? Should the tip be closee to the top or bottom of the urn?

Offline BOB357

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Re: Thermometer/temp probe placement
« Reply #4 on: March 08, 2018, 02:18:02 AM »
Without recirculation you're going to be hotter closer to the element and cooler around the edges further from the element. Stirring often is probably your best bet with an electric urn.

You could buy a cheap ice chest to mash in and just use the urn to heat your water. Every system has its trade offs. It's just a matter of working around them.
Bob