Temperature differential in mash tun

I have a 15 gal mash tun from More beer. Tun is 13" tall and I have a blichmann brewmometer installed in the side about 6" up. I use the short temp probe less than an inch and a half long. I brewed Sunday and used a second temp probe stuck in the center of the mash. I calibrated both probes to with in .2 degrees. While brewing I noticed middle mash temp was 10 degrees off from the brewmometer. Any thoughts on this? Thats a big differential in temp. What size temp probes do other brewers use in their mash tun?

Brew-ta-sauraus said:

I have a 15 gal mash tun from More beer. Tun is 13" tall and I have a blichmann brewmometer installed in the side about 6" up. I use the short temp probe less than an inch and a half long. I brewed Sunday and used a second temp probe stuck in the center of the mash. I calibrated both probes to with in .2 degrees. While brewing I noticed middle mash temp was 10 degrees off from the brewmometer. Any thoughts on this? Thats a big differential in temp. What size temp probes do other brewers use in their mash tun?

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Mash temps vary from top to bottom, side to side. That is normal. I would guess the middle temperature was warmer? If the SS tun is not insulated it will lose a lot of radiant heat and I could understand the difference.

I *think* I use the same mash tun as you and I have made a removable reflectex jacket for it. I also have an electric HLT with HERMs coil to help keep mash temps more stable.

IMHO, if you are going to use a stainless steel MLT you need a RIMS or HERMS to keep your mash temperatures where you want it.

Stir until your arm feels like its going to fall off. Then stir some more. Calibrate both of your thermometers too.

rcrabb22 said:

Mash temps vary from top to bottom, side to side. That is normal. I would guess the middle temperature was warmer? If the SS tun is not insulated it will lose a lot of radiant heat and I could understand the difference.

I *think* I use the same mash tun as you and I have made a removable reflectex jacket for it. I also have an electric HLT with HERMs coil to help keep mash temps more stable.

IMHO, if you are going to use a stainless steel MLT you need a RIMS or HERMS to keep your mash temperatures where you want it.

Click to expand...

I have added an insulating jacket (reflectix) and top as well. Yes the temp in the middle was 10 degrees warmer then on the edge where the brewmometer probe is. The insulation has helped a ton with keeping the temp stable. i just have never checked the temp in the middle before I always have gone by the brewmometer. I was surprised by the difference of 10 degrees. I also noticed that the edge temps drops while the middle temp remains constant. i bsaically didnt adjust temp at all on my last brew. I stired every 15 min but the middle temp stayed right at 154 degrees the entire hour I mashed.

Do you think going by the middle mash temp is more accurate to a mash temp then using the edge temp with the brewmometer? Do they make a brewmometer with a longer temp probe (say 6") to get closer to the middle of the mash?

chumpsteak said:

Stir until your arm feels like its going to fall off. Then stir some more. Calibrate both of your thermometers too.

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I calibrated both therms before mashing and they were only .2 degrees off.

Then you're not stirring enough.

Are both your probes bi-metal (like the blichmann brewmometer ) or is one a digital probe?

Bsquared said:

Are both your probes bi-metal (like the blichmann brewmometer ) or is one a digital probe?

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One is digital but i boiled water with both of them and temp was only .2 degrees off on the digital.

This could be it. but Im not sure it's just a hunch I've had but have not spent the time to confirm.

Bi-metal thermometers are composed of two different metals that are wrapped together along the shaft, so they will end up giving you the average temp across the length of the probe.

With a digital thermometer, it is measuring the temp at the point where the sensor is in the probe shaft, so it will be more sensitive to hot spots.

I reserve the right to be wrong on this one, like I said its just a hunch I've always had, and why I always go by the temp on my bi-metal thermometer.

not sure you could ever get around this problem without recirculating and measuring the temp of the liquid rather than the grain bed.

I use a Blichmann kettle for a mash tun with the Brewmometer installed. I recirculate the mash with a pump and direct fire to maintain mash temperature as needed. I monitor the temperature using the Brewmometer and via a Thermapen stuck into various places in the top of the mash. My experience is that he Brewmometer temperature responds more slowly. The temperature measured in the top of the bed or liquid return can be 3 to 5 degrees different from the Brewmometer.

bumstigedy said:

I use a Blichmann kettle for a mash tun with the Brewmometer installed. I recirculate the mash with a pump and direct fire to maintain mash temperature as needed. I monitor the temperature using the Brewmometer and via a Thermapen stuck into various places in the top of the mash. My experience is that he Brewmometer temperature responds more slowly. The temperature measured in the top of the bed or liquid return can be 3 to 5 degrees different from the Brewmometer.

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Thats what I have found as well. I stopped using the stick therm to check temp. I now rely on the brewmometer solely and the beer seems to be good.

Just remember to calibrate the brewmometer frequently

It is easy to bump it and screw up the calibration.