Bigger mash tun...bad idea?

How much homebrew are you going through per month?

I have a 15 gal rectangle cooler and I'm happy. I have a 15 gal kettle and can knock out 10 gal of session beer or parti-gyle a barlywine and a session beer afterwards.

The better question back into your court is: "What are your expectations of a 30 gal cooler? You could make about 18-20 gal of barleywine at a time, depending on your recipe.

Play with this mashing volume calculator at the bottom of the site"Can I Mash It?":

https://www.rackers.org/calcs.shtml

 

If you need bigger, try Walmart. My rectangular cooler holds around 28 lbs of grain and cost $25.
My problem with a large cooler is when I am making a session ale ,say 4.5 abv. The thin grain beb does not filter out fines so well. So I bought a smaller colder for session beers. It barely holds 14 lbs, but the fines filtering is improved.

 

I have a 15 gallon kettle as a mash tun for 5 gallon batches. I would never go back to a smaller mash tun. It's a little over-sized for most beers, but not so much that I can use it, and I brewed a barleywine that had a SG of 1.107 that was all grain in a single mash. I like the versatility, but you have to be careful going too large (and the mash tun setup decides what "too large" is).

 

Think about whether you might ever have to lift and carry that big bulky cooler when it's full.

 

A 10 gal mashtun will be sufficient for just about any 5 gal batch (~27#s). A little extract in a big beer will go unnoticed, imho.

 

That is true. I still wanted to be able to do a 1.110 OG beer with no extract though...

 

A 30 gallon mash tun is big.

How big? At 1.25 qt/lb, it will hold 70 pounds of grain with some room to spare. Unless you're routinely making 20 gallon batches >1.110, it's *probably* overkill. It may also make smaller batches/lower-gravity brews problematic (unless you're planning to keep the smaller one for those). Kettle size is also a consideration. i.e. can you boil 20+ gallons? Are do you plan to boil two smaller batches from the same mash?

 

One negative of too much space is loss of temp. In my expeience the more air space left in the tun makes it drop temp quicker. Nothing probably to really worry about, but a data point.

 

I agree with HopsintheSack. I have a 20 gallon SS Mashtun (which I love). But recently brewed on a colder day (55 degrees which is cold in SoCal). I nailed my mash temp with my strike water, but then watched it quickly go down to 135 degrees. It was a 12 lb batch so over half of the mashtun was dead space. The beer ended up fermenting down to 1.003. Extremely dry and extremely disappointing in flavor when I kegged it. That being said, I was able to fit 40 lbs of grain in this 20 gallon mashtun on another day and made an exceptional 10 gallon batch of double IPA. So if I can fit 40lbs in a 20 gallon mashtun, I would say 30 gallons is definitely overkill unless you are brewing 15+ gallon batches.

 

I think the argument is not against going bigger, just not that big. That's a cooler for storing a body.

 

Yeah the only real draw backs I can think of would be heat loss due to dead space and volume of wort left behind depending on type of false bottom.

 

I think grain absorption is one of those factors that depends on your equipment. I found that my larger rectangle cooler retained more water then my round beverage cooler. I assume due to the taller the tun that the deeper grain bed is affected by gravity/space time and draws more fluid out?

 

No, there's nothing inherently wrong with the rectangular geometry.

It sounds like you have already, but if not, review Palmer's appendices C & D for more info on that front.

Re: sizing... all I can offer is my experience. My most common batch size (for planning purposes) is 11.5 gallons post-boil - because I know I'll lose some to the kettle, some in the chiller, some in the fermentor, etc and it's a guarantee that I'll net two full kegs when all is said & done.

I hit 81% efficiency consistently in a converted half-barrel keg with false bottom (bought used w/o the false bottom for $65).

For a recent batch of pilsner (OG 1.049), I used 18.4 lb of grain @ 1.3 qt/lb. Total mash volume for that batch was 7.5 gallons (or, roughly, ~ 1/2 the tun's capacity). Depending on the boil time, I'll collect 13.25 gal (for 60 min) to ~ 15 gallons (for 90 min) of runoff.

I could scale the same recipe to 20 gallons, and still have room to spare in the tun, OR double the gravity (would be pushing the limits of the tun's capacity @ 1.3 qt/lb, but could cut that ratio down if necessary.

Point is, unless you want to make more than 10 - 12 gallons of high gravity beer, there's no need to go much bigger than a 15 gallon working capacity for your tun (note that chest cooler stated capacity almost always includes the volume of any recessed area under the lid - useless space wrt brewing, so a '60 qt' cooler won't accommodate a 15 gallon mash volume, etc). Something like this is probably in the ballpark:

https://www.grainger.com/product/IG.../rp/s/is/image/Grainger/15F160_AS02?$smthumb$

 

Yeah

I believe my mash tun is a 70qt Coleman Xtreme cooler. It worked great for big beers and 10 gallon batches. I don't know if I ever did a big 10 gallon batch in it, but I think I did.