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Too Much Boil Off?

northhouguy

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Feb 14, 2012
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Location
Spring, TX
I have a 10 gallon  Blichmann Boilermaker on a Blichmann  burner.  My boiloff is running a bit more than 2 [gal] per hour.

That seems excessive to me.  Am I boiling too hard?  A "rolling boil" is pretty subjective.  On the other hand, maybe it's just a characteristic of the equipment.

This weekend after a boil I turned the propane  off w/ the bottle valve and marked my regulator so I know  where to turn down from, if need be.

Any thoughts or comments?
 
I, m no expert but I keep it to a nice rolling boil.
 
Humidity and temperature can affect the boil-off rate. I, too, have the 10-G Blichmann kettle and on average I boil-off about 1.3 to 1.4 gallons in an hour and I run a fairly aggressive boil. Not too vigorous, but a fairly good rolling boil.

Your high boil-off rate is most likely due to the burner being up just a bit too high. While not necessarily a bad thing, 2 gallons per hour is quite a lot, and you can certainly get away with less. Try throttling it back a bit on your next brew and see what your rate is.

It will become important to be able to predict boil-off when calculating your total water in a recipe.
 
Good advice, Phil.

I'm going to back off on the gas a quarter turn and see  where that gets me.  I'll use the midpoint of your range as my target.  I'll tweek it a little over the next two brews and see where it lands.

Thanks.

Fred
 
Keep in mind that atmospheric temperature also plays a role in boil off.  During cold winter days you'll get quite a bit more boil off.  Also, I like to keep a gentle rolling boil.  As long as the surface of the wort is bubbling, you are boiling vigorously enough.  You want the wort to move throughout the boil, to sort of circulate if you will.  There is no need for huge bubbles that threaten to leap out of the pot!
 
ArrogantBastardAle said:
Keep in mind that atmospheric temperature also plays a role in boil off.  During cold winter days you'll get quite a bit more boil off.  Also, I like to keep a gentle rolling boil.  As long as the surface of the wort is bubbling, you are boiling vigorously enough.  You want the wort to move throughout the boil, to sort of circulate if you will.  There is no need for huge bubbles that threaten to leap out of the pot!

This.

Boiloff should be less than 15% per hour. for a 5 gallon batch that generally means about 1 to 1.25 gal per hour.

Any faster than that and you will create odd flavors. These aren't very noticeabl in darker beers like porters, and stouts.  But, in blondes and light hhybrids they are very noticeable.
 
I'll admit to being guilty of taking "rolling boil" too literally, as well. I use a converted keggle, and only do 5G batches. With a rockin' and rollin' boil, I was ending up with <4.5G in the fermenter, and my hop filtration setup is pretty efficient. I'd end up sparging more to try to offset this, but for whatever reason--probably my kettle physics along with the flame being too hot and high--I'd still end up short.

A few months ago, I finally had the opportunity to join another homebrewer in a brew session. He had his burner turned down so low that there was barely a simmer breaking on the surface. There was still boil off--no question about that--but I argued politely with him using the conventional wisdom that a rolling boil was needed for all those wonderful chemical reactions we count on to create beer magic. He just shrugged and said that's what he'd always done and had no issues. I bit my tongue.

On my next brew day, I thought that I'd just see what would happen if I backed off on the flame. I'm never that accurate with my volume measurements--"close" is good enough for me--but I was a little more diligent this time. Sure enough, I got boil off, and this time I actually wound up with my target 5 gallons in primary. I still got hot break, and good hop extraction, and the concentration of flavors, plus I probably used a lot less propane (this is subjective, but my 20# cylinder is lasting for quite a few more brew sessions now). That's a lot of wins, if you ask me.

My grasp on chemistry and physics and thermal dynamics is tenuous at best, but the important thing I took away from this is that the wort doesn't need to be boiling (or at least boiling hard) for evaporation of water to occur. Boiling, and the degree to which the boil is vigorous, just accelerates that rate. Mind you, that's simply observational evidence and not empirical.
 
Hi all, just throwing this out there. I built a 58L liter kettle with a 4500w electric heater element. The first boil test I did (only water), I could only get my water to 96C (i aborted the test since it wasnt a boil per se). A slight churn in the water but not what I'd call a boil. I added a wrap (an insulated aluminum car shade for a windshield and hit 99C with an active boil (only water). My boil off was 7L for the hour (pre-boil 30L post boil 23L) That works out to a 23% boil off. I dont think it would make much of a difference in the boil off with water in comparison to wort but is there?

This is only a 3C difference.... i guess i should do a boil test at 96C and see what my boil off is at that temp? I'm at sea level so elevation isnt going to be a factor. Or is the 15% boil off just a figure brewers try not to go over.

 
This is just an fyi from my days as a welder (many years ago in a steel mill).

When you open the valve on your gas tank, you only need to open the main valve a 1/4 turn.  Any more than that potentially wastes propane.  You can then open your regulator the desired amount to get to your preferred rolling boil. 

One beneficial side effect of only opening the main valve a 1/4 turn is that your propane tank is likely to freeze up.

If it does freeze up, your propane won't flow out of your tank.  If you have trouble with your tank freezing up (usually occurs when the tank is close to empty), just place your propane tank in a container of water.  The water acts as a heat sink and keeps your propane tank from freezing up.
 
I'm going to be brief (on lunch hour). I'm running 220 volt 5500 watt heating elements. The boil tends to be more centralized around the heating element,  different from using a propane stove heating the whole bottom of the kettle. My first test run of this HERMS system boil off 2.5 gal per hour at 90% duty cycle. Reducing it to 45% duty cycle, boil off 1 gal per hour at 4400 feet. Did not have time to convert that to metric. 
 
steve45ca said:
I built a 58L liter kettle with a 4500w electric heater element....

hit 99C with an active boil (only water). My boil off was 7L for the hour...

For a full kettle of 50 liters, your heating element is slightly undersized. I'm not going to go into all the math, so here's the cliff notes:
  • Your heat element generates 15.35K btu, tops.
  • It takes about 4.5K btu to heat that volume at 100C.
  • Probably at least 500 btu to maintain 100C.
  • The slightly lower temperature is due to ambient heat loss (unknown amount) as you noted, plus the energy required to create steam (about 2200 btu/liter/hr).
  • Seven liters of steam in 1 hour require 15.4 btu.
  • That's a deficit of at least 550 btu.

You need more headroom. Most likely an element of 5500 Watts minimum is needed to create a full volume boil.

For beer making, the steam needs to be generated within the wort in order to strip off DMS volitiles. Simple surface steam isn't going to suffice. Plus, full hop isomerization is realized with agitation, in addition to heat. A rolling boil creates the needed agitation.
 
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