How do I calculate my thermal capacity of my MLT

I am getting ready to step up to AG and purchase all the necessary equipment to batch sparge. I want to create my own recipe, but I am having some trouble understanding some of the calculations. I am using BeerAlchemy to formulate a Belgian Golden Strong Ale. My questions are...

How do I determine my water volumes and temperatures mashing and sparging? I am shooting for 5 gal post boil.

How do I calculate my thermal capacity of my MLT?

I think thats the big problems for the moment, but I am sure more will come up. Thanks in advance!

If you haven't done so already, I would suggest giving the trial versions of Promash or Beersmith a try. Both will handle all the volume and temperature calculations you are wondering about, as well as many others. As far as the thermal capacity, Beersmith has a default setting of .300 for a plastic MLT and I believe it is also the default setting in Promash.

I think BeerAlchemy is a Mac program so he probably can't run those others.

To the OP, check out howtobrew.com, it has the formulas for figuring out the volumes you need. For for your mash tun thermal mass, if you pre-heat your tun with 4L (~1G) of hot water before you add your strike water your thermal mass will effectively be 0 and you don't need to worry about it.

That helps alot! Thanks! They use .2 in their calculations. Is .3 closer to the rubbermaid thermal capacity? What about the sparge water temp/volume?

Also, how do I determine the qt/lb ratio for each mash?

baker0408 said:

Also, how do I determine the qt/lb ratio for each mash?

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For the most part you can just use a standard of 1.3 qt/lb, if you want to get into the nitty gritty read howtobrew.com so you can see what the various affects of mash thickness are.

bradsul said:

if you pre-heat your tun with 4L (~1G) of hot water before you add your strike water your thermal mass will effectively be 0 and you don't need to worry about it.

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It's not really that easy. If using a bucket or a kettle that is .04" thick and you keep the water in contact with all of it then yes. But if it's a thick cooler it's going to take a little more then just adding a gallon of hot water.
With a cooler there is a LOT of surface and mass to warm up. Because you are not just warming up the surface but all the foam behind that surface. I would use 3-5 gallons to preheat the tun at like 170* (depending on the temp of the tun to start with) then I would use that water for sparge water. So you're not wasting any water just a little gas to heat it the first time.

FSR402 said:

It's not really that easy. If using a bucket or a kettle that is .04" thick and you keep the water in contact with all of it then yes. But if it's a thick cooler it's going to take a little more then just adding a gallon of hot water.
With a cooler there is a LOT of surface and mass to warm up. Because you are not just warming up the surface but all the foam behind that surface. I would use 3-5 gallons to preheat the tun at like 170* (depending on the temp of the tun to start with) then I would use that water for sparge water. So you're not wasting any water just a little gas to heat it the first time.

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Not disputing what you said, just offering up from my own experience. It takes about 4L of hot tap water to preheat my 48QT rectangular cooler such that setting promash to a thermal mass of 0 causes all the heat calculations to be correct.

Obviously everyone needs to experiment with their own systems to find what works for them, that's part of the fun.

During your first couple of AG batches keep track of your mash temps after the strike water is added. In my case, after a few batches I noticed i was losing about 16.5 degrees so now I just heat my water 17 degrees higher than my mash temp and I end up real close to my target temp.

As far as the MLT thermal mass goes, a cooler has very low thermal mass and poor conductivity. I just boil about 75% of my strike water, dump it in the cooler and close the lid for 10 minutes. Then I adjust the water temperature to strike. I adopted this method, because my brewery is not heated & can vary from 40-100F.