Boil off rate

[LONG CALL BREW]

Anyone out there have a rough idea what the boil off rate might be for a stainless pot that measures 16” diameter and 18” deep. I’m using it for the first time Friday and don’t have time to run a test boil. Thanks in advance for any replies.

 

[Nosybear]

Start with 1 gallon per hour, then determine the actual rate empirically - by observing your results. Too many variables for us to predict. And remember, if you have some DME and boiled water on hand, you can always adjust the OG to where you want it.

 

[J A]

Mine are 16" and I run 1.5 gallons per hour at a pretty vigorous boil. Better to underestimate slightly because you can just top up near the end of the boil for instant accuracy.

 

[ACBEV]

Boil off rate can vary considerably depending on ambient conditions, equipment and other factors. In the summer my boil off rate is 0.091L per minute, in my last boil in cold conditions it was 0.056L per minute. Over a 90 minute boil I ended up with 3L extra wort.

So I learned a lesson to keep my heating on in my brew shed and/or insulate my boiler too.

Although you don't want to do a test boil, I recommend you do, especially if its your first time using this kettle...

Make up a sugar solution to 1.050 and boil for 60 minutes... subtract post-boiled volume from pre-boil and divide by 60, this will give your boil off rate per minute. Which is useful if you do varying lengths of boil.

 

[J A]

Make up a sugar solution to 1.050 and boil for 60 minutes...

Just plain water will do...but our OP says he doesn't have time to do a test boil.

 

[Nosybear]

So assume 1 G/H, then be ready to adjust once the boil is complete. Have some DME and some boiled water on hand. If the OG is too high, add water. Too low, add DME. There's a calculator on this site to help. But be aware, the boil-off rate is not some universal constant. It will vary from batch to batch so knowing how to adjust OG (and when it makes sense to do so) is a valuable skill.

 

[BOB357]

You can do a boiloff test in 15 minutes. Just multiply the difference in starting and finishing volume x 4.

 

[Nosybear]

You can do a boiloff test in 15 minutes. Just multiply the difference in starting and finishing volume x 4.

Problem is that the more you boil off, the less volume to carry the heat - in other words, the boil-off isn't linear. Best to do the full hour, although Bob's method would get you fairly close, at least within the range of my RDWHAHB and correct when the boil is over.

 

[BOB357]

I should have said to start with 5 or 6 gallons.