# Math question

Let’s see if I can do some brewing math correctly. Hypothetically, let’s say I wanted to brew 20 gallons all-grain at a time. So, to obtain 20 gallons of wort, I need to boil down 26 gallons? and my kettle should be 30 gallons (or so) to avoid boil over? I would need 40 lbs +/- of base malt, and … how large should my mash tun be? (assuming I sparge with equal amount of water to obtain the 26 gallons necessary for boil.

How much volume does 40 # of malt occupy, and how much of the initial infusion will be absorbed?
How much water will I need for infusion, and how much for sparge (same amount roughly?) st t?
Just trying to daydream about building a large system someday.
Helps my peace of mind if I have an equipment list complete with prices. So I know just how unrealistic it is to dream about.

I think what you need is here:

Looks like you’re planning on boiling off 6 gallons. I’m guessing that’s based on 1.5 gallons for a 5 gallon batch x4. I don’t know from experience, but I doubt you’ll boil off 6 gallons.

Logic would tell me that for the same size pot, a boil is a boil and whether you start with 5 gallons or 15, the amount boiled off in an hour is approximately the same. To be safe, I would assume a little more for the larger volume due to the increase time of getting to boiling where the wort is evaporating and cooling off where the same thing is happening.

Start with the assumption of a 10% boiloff (of the kettle’s volume, not the wort volume) for a 90-minute boil, so a 30-gal kettle will lose about three gallons. You can produce 20 gallons of wort with a 24-gallon kettle (at least I can, using fermcap to keep from boiling over), but bigger would be better, and a 30-gallon cooler works great for a mashtun for this size batch (you could go smaller, but why?). You’ll need a big burner - my KAB-6 with 230K BTUs takes a while to get 24 gallons to a full boil. And chilling is a challenge - if you’re going to use an IC, get a big one and use a whirlpool setup with a pump or else you’ll be standing there all day and stirring. I just bought a plate chiller for my setup, haven’t used it yet, but I’m looking forward to much faster chilling times for the big batches.

Boil off rate is dependent on the opening of the kettle. Short/wide kettle will have a higher boil off rate than a tall/narrow kettle of the same volume.

If you have your MT, start with the “can I mash this” calculator RiverStreet linked to. See what the max amount of grain it will hold.

Then develop your recipe, or copy one of NB’s and increase it to fit your finished volume. Or the max that your MT will hold.

http://gnipsel.com/beer/software/beer-software.html
to help get your water volumes.

Boil off percentage is not a good way to do it. With a standard pot and burner you will boil off the same volume per hour. If you use percentage, then the percentage goes up for each hour that you boil.

If you are going to get another pot and burner you’ll need to do a trial run to find out its boil-off.

My experiences to date:
I do 20-22 gallon batches on my system all the time. I have a 25 gallon Megapot which actually holds a tad over 26 gallons. I fill it to within an inch of the top and usually have 22 gallons left after a 75 minute boil.

I have three different sized mash tuns: 48qt for <29 lb; 60 qt for <44 lb and 120 qt for 45-75 lb grain bills. You should fly sparge so that your burner can heat up the runnings AS you are collecting them.

My brew cart runs on NG from the house and the burners are 58,000 BTU on BK and 35,000 BTU on HLT.

My chilling is done very fast (22 gal in 10 minutes) where I run thru twin Chillzilla CFC’s in series powered by a March 809 pump with a 815 impeller for max flow and pressure.

Total time from start to finish is 4.5-5.5 hours. Feel free to reference my website for lots of pictures and ideas.

wow, guys, awesome level of response. Thank you!
also very glad for the experienced input from Mullerbrau!
cheers!

[quote=“TG”]Boil off percentage is not a good way to do it.[/quote]As long as you specify a boil-off percentage as a function of the starting volume and boil time it’s the same thing. A 24-gallon kettle that loses 2.5 gallons in 90 minutes has a ~10% boiloff or a 1.6 gal/hr boil-off rate.

Volume per hour just works better for different boil lengths and different boil volumes.
E.G. you boil off 1 gallon out of 10 gallons of wort. That is 10%. Now say you want to double the batch and you boil off 1 gallon out of 20. The boil volume is still the same, but now the percentage is 5%. YMMV.

Here is a link to some details of my 20 gallon system that you may find helpful in your research:

http://hbd.org/discus/messages/366/3362 ... 1339813504

Brewbeer22, I am very impressed with your system! I see you have a cream ale you are serving? I just made one on Monday evening. The kit came from N.B. If you don’t mind, I have a few questions. This is the first cream ale I ever made. I boiled in a 15 gallon pot, I started with 7 1/2 gallons of wort after batch sparging the grain. I want to wind up with about 61/2 gallons after the boil. Unlike the boils in the past, which were pretty aggressive, I toned it down quite a bit to where the wort was just doing a slow roll,mostly in the center of the kettle. I did this because the other three all grain kits I brewed had a volume loss of over 3 gallons after a 1 hour boil. Is a slow boil OK to do? Another thing I noticed was all the suspension of fines in the wort. After the wort was cooled and I removed a sample for the hydrometer, I had to let it sit over night for the solids to settle out before I put it in the tube to measure the SG. I did notice a lot of fine grain in the bag before I dumped it in the mash tun. Did you ever experience the same thing?

+1 Brewbewer22. I like your setup, also, and will certainly put to good use some of your ideas. Especially for your brew rack. Pumps and plate chillers were not in my original budget, but appear to be most necessary, so I’ll have to make adjustments. On the plus side, I discovered a large enough cooler is not really expensive, and the brew kettle doesn’t need a thermometer or valve, so long as I use a thrumometer and a pump. So, couple of hundred dollars savings right there.