Having trouble getting consistent temp readings in MLT

[jaxn]

I'm fairly confident that I'm hitting the temps overall since my beers have been coming out fine, but when I take readings after dough-in, the variation from one part of the MLT to another is substantial.

I'm using a 60qt Ice Cube, and have been having the same problem with both 5-gal and 10-gal batches.

I pour the ~168 degree strike water in the MLT, let the MLT warm up, dough in, stir a lot, let it sit for a few minutes, and then check temperature. I feel confident in the thermometer because it's a Thermapen, but I'm getting temp variations of more than 10 degrees from one corner to the other. One spot will read 153 F and another will read 137 F. I know this isn't normal.

Then even after the 1 hour mash, I'm still getting a lot of variation.

Any suggestions?

 

[david_42]

Use more water in your mash, try 5:1 or even 7:1 by weight. This makes it easier to stir and the additional thermal mass will minimize temperature drops.

 

[cactusgarrett]

How long do you let your MLT pre-heat with your strike water prior to doughing in?

 

[jaxn]

How long do you let your MLT pre-heat with your strike water prior to doughing in?

About 5 minutes.

 

[McKBrew]

You might try heating a little longer.

Do you brew indoors or out. The igloo ice cubes I am familiar with are lacking in the insulation department. Not as thick as it needs to be. I had one I used to keep sparge water warm and it didn't do well at all.

You might consider wrapping some sort of insulation around the out side.

 

[jaxn]

I might try heating a little longer. But I think I might not have gotten my point across. My issue isn't heat loss over time. It is heat variations in different parts of the cooler at the same time.

 

[Homercidal]

I see this in my cooler as well. It's a rectangular Coleman cooler, and one side is consistently 2 degrees warmer than the other. I use the cooler side for my temp.

I think the difference is the manifold layout. I get less stirring on the spigot side, even though I really try to mix it all up well. There is a small length of plastic tubing running from the center of the manifold to the spigot. I think some warm grain gets stuck under there.

 

[cactusgarrett]

I might try heating a little longer. But I think I might not have gotten my point across. My issue isn't heat loss over time. It is heat variations in different parts of the cooler at the same time.

I understand, but the two can potentially be related due to homogeneity of temps (or lack thereof) across your pre-heated MLT. Pre-heating for longer is an easy initial step to take to eliminate that variable. I like david_42's idea of a larger thermal mass (higher water:grain ratio) to buffer temp changes, too.