Large mash tun and heat loss

Hello folks,

I was hoping you could lend me your thoughts on this.

My buddy and I are going to up our capacity to 30+L batches pretty soon and we are looking at a 66L mash tun from my home brew store. I am hoping for this to be a good long term solution giving us freedom to brew to different capacities. It is seemingly made from a very high quality cooler and they assure me heat loss won't be an issue.

However, I want to know whether this will be an issue when for example we brew a standard 5 gallon batch. Even at 30L you are still going to have some head space. Does anybody here brew with a large mash tun such as this? And have you experienced problems when mashing smaller batches?

Thanks in advance!

Graeme

I use a 152 qt. cooler for large high OG batches, but still use my 48 qt. for smaller batches. I think that's the best way to go.

Denny said:

I use a 152 qt. cooler for large high OG batches, but still use my 48 qt. for smaller batches. I think that's the best way to go.

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Prob is, my current mash tun is a little small and we need to up it anyway. I just figured we would get a high capacity mash tun that will last us many years.

Bump. Any help would be greatly appreciated guys!

What kind of mashtun is it you are looking at? Just curious, if there were a lot of head space is there anyway you could just cut out some styrofoam and wedge it in there to make a smaller chamber. Or maybe just wrapping a wood block in some kind of food grade insulation that would snugly fit in there. Not sure if that would work depending on the cooler but that could hypothetically cut the size in half and I'm sure it wouldn't be perfect but it would be better than a cooler that was a third full.

You are going to have more heat loss. The amount, I can not say. To minimize heat loss you need to consider surface area to volume. The best shape for this is a sphere, but of course that is not practical. Realistically, you want the vessel to be as full as possible, and have the contents be as deep as the vessel is wide. If you use a very large cooler, you are going to have a greater heat loss if it does not have a very good SA:V ratio. Your contents may only be 12 inches deep, but that will transfer to the headspace and dissipate through the walls to external air.

I suggest you keep your original and have the one mentioned for larger scale brewing.

I occasionally borrow a mash tun like you are describing. The large amount of head space simplifies stirring, but does indeed have an effect on strike temps. This is easy to simulate and thus a calculation can be made to adjust for it. The bigger problem I found is that if you feel the need to go in and out of the cooler during the mash process, the large head space rapidly fills with ambient temperature air each time. This quickens the drop in mash temps. However, this is hardly a deal breaker as you can obviously avoid it in most instances. Cheers.

I have a 100qt and the one time I used it for a normal gravity 5g batch it lost a fair amount of heat. I definitely recommend getting some sort of divider to stick in there to cut the size down.

A 1/2 barrel keg (US size, so 15.5 gallons) would work. I've mashed for 10 gallon batches in my keg mash tun. Depending on how you set up the sparge setup and/recirculation fittings will give you the total grain capacity. There are options for insulating the keg mash tun too. I have a carbon fiber welders blanket glued to mine. I also have more I can wrap around it to increase the insulation value. You can also use reflected material around it (don't direct fire with that on though). I prefer to be able to direct fire the mash tun for temperature control. IME it works far better than trying to increase the grain bed temp by adding boiling water to a cooler mash tun. The only other decent met on (IMO) would be either a RIMS or HERMS system. Both require more hardware though.

Thanks for your replies guys, they are much appreciated. It's basic science that a large mash tun like this would suffer heat loss when half full I guess. The problem is my home brew store doesn't really do an in between. They go from like 30L mash tuns to the 66L I am describing. Somewhere in the middle would be ideal. My DIY skills are non existent so I don't think I'll be attempting building one!

Wedging some Styrofoam in there as suggested above could definitely be a good solution. I'll have a good think about it!

Cheers!

I think a 66L cooler would be fine for 5 gal batches. Just preheat the mash tun and cover the mash tun with a heavy blanket to hold the heat in.

My DIY skills can't be any better than yours, but even I can build a Cheap'n'Easy mash tun. I still think the ultimate solution is to have 2 mash tuns, one for smaller batches and one for larger.

The issue really is that we need a new mash tun regardless. I have a large boiler which we really need to utilise. So 30L batches is about where we want to be going forward. A 66L mash tun is probably a bit too much for this kind of thing but as I said previously it's their best mash tun and anything they have smaller is too small