What is your boil off?

[VanHorneDog]

Ok, so I am going to scale up from 5 gallon batches. I typically boil off between 1 and 1.5 gallons (depending on boil vigor and other factors).

So what i am wondering is should i expect to boil off the same amount with a 15 gallon batch? as in i need about 16-17 gallons pre boil? or will the greater surface area and higher burner heat mean i will boil off 2-3 gallons?

So, essentially im wondering what peoples pre-boil volumes are for their various sized batches.

Looking at 15, 20 or even 25 gallon batches. so those numbers are very interesting for me, though if anyone does 1bbl plus stuff im curious about that too.

 

[Reelale]

Your rate will be the same regardless of batch size. The most important variables are relative humidity and the vigor of the boil.

 

[Dan]

I've read the volume you start out with doesn't matter the boil off rate will be the same. To get an idea of my boil off rate in a 15g keggle I boiled 5 gallons of water a few times and averaged out to be 1.5 gallons of boil off on a roiling boil, not crazy vigorous. Seems to hold true when I do larger volumes for 10 gallon batches.

 

[BBKing]

I was wondering the same thing recently, as I'm looking at increasing my batch size.
Glad I happened upon this.

 

[BBL_Brewer]

Your % boil off rate should be fairly close. I lose about 15% whether doing 5's or 15's.

 

[eknee]

Wait, is it a fixed amount or is it a percentage? 15% of 5 or 15 gallons is a significant difference.

 

[pelipen]

If you have 3 gallons, and boil off 1.5 gallon per hour, you'll be left with 1.5. That's 50%.

If you have 1 gallon and assume 50% per hour based on your 3 gallon figures, you'll burn your pot.

Use a rate, not a percent.

 

[day_trippr]

It's not a percentage. Boil off rate is a function of surface area, humidity and the degree of "vigor" of the boil...

Cheers!

 

[BBL_Brewer]

It's not a percentage. Boil off rate is a function of surface area, humidity and the degree of "vigor" of the boil...

Cheers!

You can certainly measure it as a percentage.

 

[Rockape66]

My rate has been in excess of 1.5 gal per hour. Still tweaking to hit target volumes.

 

[luhrks]

Mine is 2.1 gal per hour. It depends on your boilpot configuration. Do timed boil with 5 gallons for an hour. when it's done cooling. You'll have your numbers.

 

[Diaperload]

It's not a percentage. Boil off rate is a function of surface area, humidity and the degree of "vigor" of the boil...

Cheers!

I'll be the first to admit that I suck at math but I know this to be true. My beer club just purchased a new boiling kettle. Same volume as the last one but it's diameter is larger.

The old brewing kettle has been in use to 10 years so the guys have a pretty good idea of the boil off rate. This new kettle is only a few batches old and we are getting all messed up because the boil off rate is way different now.

 

[Calichusetts]

Barely a vigorous boil...if I stir it it will go nuts, but mine is a lowly .6 gallon an hour...fantastic considering I do small batches

 

[SpottedDogBrewing]

Depends on size of pot and how vigorous the boil. My 15 gallon kettle had a boil off rate of 15% and my 40 gallon pot has a 20% boil off rate (each pot with a different burner also) Just keep track of what you start with and what you end with for a few brew sessions and average. As long as your setup stays the same your boil off rate will stay the same. If you change boil pot size or even the burner you may have to reevaluate the boil off rate again..
cheers

 

[pelipen]

I'll be the first to admit that I suck at math but I know this to be true. My beer club just purchased a new boiling kettle. Same volume as the last one but it's diameter is larger.

The old brewing kettle has been in use to 10 years so the guys have a pretty good idea of the boil off rate. This new kettle is only a few batches old and we are getting all messed up because the boil off rate is way different now.

definitely. Going from a 20" wide pot to 24" doesn't look like a lot, but the surface area is 1.44x larger, which is likely to be noticeable.

 

[mrgstiffler]

Mine is just over 1G every 30 minutes

 

[matt2778]

Pot diameter is everything when it comes to boil off. When I switched from a 36quart to a 60quart pot my boil off went from 1.25gph to 2gph. Volumes remained unchanged as did the burner but the pot diameter went from 14" to 18".

 

[solavirtus]

Mine is about 1.5 gal per hour in the cold (and relatively dry) Michigan winter. It get closer to 1.25 gal per hour in the humid summer here. My pot is also relatively wide 50qt, and I usually maintain a moderately vigorous boil.

 

[pelipen]

Pot diameter is everything when it comes to boil off. When I switched from a 36quart to a 60quart pot my boil off went from 1.25gph to 2gph. Volumes remained unchanged as did the burner but the pot diameter went from 14" to 18".

Your surface area increased by a factor of 1.65.
1.25 g * 1.65 = 2.06 g.
empirical evidence supports the math. I like it when that happens.

 

[ReverseApacheMaster]

I am boiling off about 0.5-0.75 gallos an hour whether I am indoors on the stove with a small batch or outdoors on the turkey fryer. It is very humid here.

 

[Jazman]

Your rate will be the same regardless of batch size. The most important variables are relative humidity and the vigor of the boil.

I would agree with that given the kettle is the same. But, I'm guessing a bigger batch means a bigger kettle.

The other variable to boil-off is the surface area of your kettle. So, if you have a bigger opening then you'll get more boil-off. If just your kettle height is different, that that shouldn't affect it.

Jaz

 

[VanHorneDog]

hey thanks guys that was very helpful.

 

[gcdowd]

I lose about 2 gallons an hour on my 5 gallon batch (start with 7 gallons), which is about 28%. My kettle diameter is large so I understand this but is this a bad thing? I thought I read somewhere that a boil off rate of 15% is ideal, not sure if true. Also, I've only boiled in winter so far and living near Syracuse NY it can be quite cold and snowy. It does get very humid in the summer here and I wonder how that will affect my boil off. We literally get like 100% humidity in the summertime. Is there any way to calc what my pre boil volume should be based on humidity? I assume I'll start needing less than 7 gallons.

 

[weirdboy]

I boil off about 1 gallon per hour nowadays. Makes it easy to calculate stuff, anyway.

 

[downtown3641]

Just tested my new kettle yesterday. I only did a 15 minute boil, but wound up with a rate of about 2 gallons per hour.

 

[Brewsncrabs]

Go here for a good starting point.
http://sigginet.info/brewing/tools/equipment-profile-helper/