Calculate the heat of empty space in the mash tune?

Hi!

I’ve a small question about equipment profile and mash tune heat.
I’ve a 45qt Coleman chest mash tune, work perfect for 10-12 gal batch as it's near full.

But last weekend, I brew with the same mash tune a 5gal batch. I lost 4° in my mash tune due to the space between the mash and the lid, more that expected when I heated the water. I completely forget to take this in mind when I was heating my water. I also thought afterwards that Beersmith has taken this in consideration. But hasn't or I forget something.
I check the box near the mash profile when I designed my recipe to take my equipment in the calculation.

It is a way to calculate this empty space to avoid the stress to boil water and compensate the temp in the mash tun  when I design the recipe, so I’ve simply to follow the brew steps “blindness”?

Hoppy regards and thx for your feedbacks,
Dom

I usually pre-heat my 48 qt. (Ice Cube) cooler with a couple of gallons of hot water from the faucet for about 20 min.. I only loose about 1 to 2 deg F during mash.

Mike

Yep, I do the same. But in this case, I've more empty space as usual an I wonder if their is a rule of thumb... or not...

Dom

The issue is not in the airspace, but in the unheated portion of the insulation.

When full, the mash is in contact with more insulation. When cooler, the insulation pulls more heat from the smaller volume.

I think the solution is to simply use more water to preheat, and perhaps give it a few more minutes.

Thx. I will try this on the next batch.

Dom