Limiting Boil Off Rate

[magnj]

I'm looking for input on controlling boil off rate. Brewing 10 gallon batches in a 15 gallon kettle. We are experiencing inconsistent boil off rates as we brew outdoors. Looking at pro hardware, I see that some equipment has only a small 6" exhaust port rather than a whole open top. Obviously we want to boil off any DMS but we also want to improve our pre-boil volume consistency. Anyone have any experience with this?

We're thinking of drilling a large hole or several smaller hols to limit the amount of exposed surface area to the elements.

Thanks.

 

[MattyIce]

What is your range of boil-off rates? I also brew out in the open, but I don't experience much variation in my boil-off. I generally maintain a pretty gentle boil though.

 

[SanPancho]

We're thinking of drilling a large hole or several smaller hols to limit the amount of exposed surface area to the elements.

what is this referring to? drilling a hole in what? a lid?

 

[magnj]

What is your range of boil-off rates? I also brew out in the open, but I don't experience much variation in my boil-off. I generally maintain a pretty gentle boil though.

15-20%

what is this referring to? drilling a hole in what? a lid?

Correct

 

[dwhite60]

Could be a relative humidity issue. Drier air will cause faster boil off.

All the Best,
D. White

 

[SanPancho]

Pro equipment is sometimes open kettle, but more often domed top with a sizable vent stack and drip condensation removal to protect against DMS falling back into kettle. Bigger the better. Even use exhaust fans at roofline.

If you want to get rid of DMS, lose the lid. a few drilled holes won't help as long as vapor still condenses and drips back in kettle.

Your best option in my opinion is to go lid off, standardize your starting volume, and always use same burner/heat level. If u brew outside then variables like air humidity, temp and pressure (wind) are out of your control. But you should still be pretty predictable summer vs winter.

You'll find that starting volume has a big effect, especially as batch sizes get smaller. Your heat level stays the same but as volume shrinks your boil off isn't straight line. It's actually a curve getting steeper as your volume shrinks. (Assuming heat, humidity, pressure are constant). so your best bet is to use constant values - start volume, heat level, time. The rest is out of your control unless you brew inside.