Any guesses why my boil-off rate is so high?

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shawnbou

shawnbou

Zyme Lord
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Looking for an answer to a question that's been bugging me.

I brew 5.5 gallon AG batches so I can leave some gunk in the kettle and some trub in the fermenter and still keg 5 gallons. But to get to 5.5 gallons at the end of the boil, I collect 8 gallons of runnings from my MLT. I take it from reading stuff online that this is a lot. Most people seem to say they're collecting around 6-7 gallons.

I boil for 90 minutes and don't start the timer until after the hot break, so it's probably more like 105 minutes. That puts me at a boil-off rate of about 1.4 gal/hour.

The beer tastes great. I don't have tannins from oversparging. So I'm not trying to solve a problem, just wondering why I seem to be boiling off so much. Could it just be my long boil? The Texas heat? My kettle or burner? Any ideas?

And what kind of hourly boil-off rate qualifies as "normal"?
 
Since someone is going to ask:

What are the dimensions of the kettle? Most importantly the Radius.

Boil off is dependent on the surface area not the total volume so it's hard for anyone else to say "with the same size pot my boil off is X" without knowing the surface area of yours.

Other things that can make a difference is the level of the boil. A gentle rolling boil will boil off less than a violent raging boil.
 
I boil off about the same amount. I start with 7 gallons for a 5 gallon batch, but only do 60 minute boils. I do start the timer after the hot break, but that happens really quickly.

I know the homebrewers in the desert boil off a lot more than I do!
 
Yep Humidity and elevation are other factors.

Have you asked what other brewers in your area experience?
 
The kettle is 14" in diameter and roughly 14" high. 9 gallons in volume.

It's fairly humid here in Austin, so guessing that's not it. But asking some local brewers is a good place to start. Thanks.

I do tend to boil pretty violently, I suppose I could dial that back if I wanted to solve this. But hey, the beer is good so maybe I'll just let it be.
 
at 1.4 GPH evaporation rate I would ask why its so low..:D LOL

I boil off 2.25 gallons per hour. I am using a keggle with false bottom but I do use a fan blowing on the top so I can turn up the 170,000 BTU burner and not have a boil over.

I think your spot on with your system man. All you have to do is make sure its the same every time and account for the losses.

Cheers
Jay
 
shawnbou said:
And what kind of hourly boil-off rate qualifies as "normal"?
Click to expand...

Yours! Lower boil off rates could be attained via taller/narrower kettle I think. Ambient temp shouldn't have much effect but relative humidity can. As long as you are collecting the right amount of wort to get you to 5.5 gal. post boil I'd say you're on the right track.
 
The best suggestion I could give is to add a measured amount of water to your pot then boil as you would a batch. At the end measure the amount left. The amount you lost is your boil off.
 
I think the premise is wrong. 1.4 gal/hr isn't a high boil off rate. If you start with 7 gallons and end up with 5.5 over a 60 minute boil, that is 1.5 gal/hr. That is a very common range.
 
You all have made me feel better about this. I guess 1.4 gal/hr isn't very high. And since I get consistent results, hit my gravity targets, and don't taste any signs of oversparging, I think I can put this one to bed.

Thanks, all. Cheers! :mug:
 
I boil off 2 gallons per hour. My kettle is roughly the same dimensions. It's pretty dry here and I brew outside. Once or twice I didn't anticipate where the sun would end up and the kettle sat in direct sunlight for the last half of the boil. I boiled off a little more that time.
 
1.4g/hr like they say isnt a lot, i start around 6.5-6.75 gallons to end at 5 gallons.

Your at a lot because you do 90 minute boils, which I have to question your reasoning for. For some styles its appropriate but for everything its just overkill IMO.
 
shawnbou said:
Looking for an answer to a question that's been bugging me.

I brew 5.5 gallon AG batches so I can leave some gunk in the kettle and some trub in the fermenter and still keg 5 gallons. But to get to 5.5 gallons at the end of the boil, I collect 8 gallons of runnings from my MLT. I take it from reading stuff online that this is a lot. Most people seem to say they're collecting around 6-7 gallons.

I boil for 90 minutes and don't start the timer until after the hot break, so it's probably more like 105 minutes. That puts me at a boil-off rate of about 1.4 gal/hour.

The beer tastes great. I don't have tannins from oversparging. So I'm not trying to solve a problem, just wondering why I seem to be boiling off so much. Could it just be my long boil? The Texas heat? My kettle or burner? Any ideas?

And what kind of hourly boil-off rate qualifies as "normal"?
Click to expand...

I recently got a new BK which is considerably shorter and larger in diameter than the old one. I went from about 1.25 gph to close to 2 gph boiloff rate. The surface area is a large factor in your rate. My new BK is tri-clad bottom and the old one was single layer. I think the better heat distribution is also a factor, but to a smaller degree.

Bob
 
Are you supposed to boil with your kettle lid on or off? I'm assuming that will effect evaporation rate, right?
 
richlids said:
Are you supposed to boil with your kettle lid on or off? I'm assuming that will effect evaporation rate, right?
Click to expand...

Always boil with the lid off. One of the purposes of the boil is to drive off the precursors to DMS and if the lid is left on these will condense on the lid and drip back into your wort.
 

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