Boil off on 11 gal batches?

Need some help on my boil off figures for going to 10 gallon batches.

Currently I am using a setup where I am boiling off roughly 35.75% of volume off in a 90 minute boil to end up with a 5.5 gallon final cold volume. These boils are starting off at 8.56 gallons pre boil due to the liquid surface area width of my BK which is quite large due to how wide it is.

Now with all of that said I am going to make a jump to 10 gallon batches here soon and utilizing the same equipment figures in Beersmith gives me almost a 15 gallon pre boil volume which seems extremely large but right on point with the current boil off values. My only concern here is the fact that I am dealing with a larger volume of liquid and it may not boil as vigorously as the smaller 5.5 gallon batch. Should I use two different equipment profiles for the larger sized batches? I have no problem boiling this larger amount of liquid having a 20gal BK but I am concerned that these figures will be incorrect due to dealing with a larger amount of wort.

Thoughts?

Fill system with 10 gallons of water and boil it for 90 minutes.

If the factor changes set-up another equipment profile.

I would think that if 3.01 G boiled off on a 5 G batch, 3.01 G would boil off on an equally vigorous boil of an 11G batch. Not so much a percentage. Can someone explain this?

Climate and boil consistent, should boil off the same amount of water in the same amount of time, not the same percentage of water.

This is just my thought and assumption.

IrregularPulse said:

I would think that if 3.01 G boiled off on a 5 G batch, 3.01 G would boil off on an equally vigorous boil of an 11G batch. Not so much a percentage. Can someone explain this?

Click to expand...

I agree that the boil off rate is more of a constant than a percentage IF you are using the same boil kettle for both. The surface area and boil strength are the biggest factors to boil off rate, though outside temp and humidity are also factors. So if you boil at the same strength with the same surface area then the amount of liquid boiled off would be the same. The total liquid volume would not be a determining factor. At least that is how I understand it.

IrregularPulse said:

I would think that if 3.01 G boiled off on a 5 G batch, 3.01 G would boil off on an equally vigorous boil of an 11G batch. Not so much a percentage. Can someone explain this?

Climate and boil consistent, should boil off the same amount of water in the same amount of time, not the same percentage of water.

This is just my thought and assumption.

Click to expand...

Brewmasters Warehouse said:

I agree that the boil off rate is more of a constant than a percentage IF you are using the same boil kettle for both. The surface area and boil strength are the biggest factors to boil off rate, though outside temp and humidity are also factors. So if you boil at the same strength with the same surface area then the amount of liquid boiled off would be the same. The total liquid volume would not be a determining factor. At least that is how I understand it.

Click to expand...

Yep, I agree. Since the surface area is the same, you should have the same boil off. Not as a percentage, but as a volume. If you boil off 1.5 gallons an hour with 5 gallons, in the same pot you will boil off 1.5 gallons an hour with 10 gallons alos.

The boil off rate (measured in gallons/hour, not percent volume/hour) may actually decline slightly since 11 gallons will require more energy to sustain a boil.

Yuri_Rage said:

The boil off rate (measured in gallons/hour, not percent volume/hour) may actually decline slightly since 11 gallons will require more energy to sustain a boil.

Click to expand...

Yes. And, if you are in fact boiling off 35% an hour I'd wager you could also stand to put less energy into your boils.

Yuri_Rage said:

The boil off rate (measured in gallons/hour, not percent volume/hour) may actually decline slightly since 11 gallons will require more energy to sustain a boil.

Click to expand...

What kind of volume are you talking about as "slight"? anything noticeable the casual brewer?

I tend to not take as good of notes as I always say I'm going to and always stress about volumes.

I'm not certain, since there are so many variables at play. The volume increase is significant enough to warrant a trial run to recalculate the boil off rate.

Yuri_Rage said:

The boil off rate (measured in gallons/hour, not percent volume/hour) may actually decline slightly since 11 gallons will require more energy to sustain a boil.

Click to expand...

This is exactly what I am talking about. I am thinking that the boil off rate will be slightly lower due to the fact that the liquid will not boil as vigorously being larger. This is the same exact kettle and setup I use for 5.5 gal batches.

This marginal percentage that Yuri was referring to may actually be calculated with BeerSmith, when I figure up the boil off estimation that I get in Beersmith for a 10 gallon batch starting with a pre boil volume of 14.95 gallons I get a 33.12% boil off rate over the course of 90 minutes.

Estimated boil off for 5.5 gal batch: 35.75%

Estimated boil off for 10 gal batch: 33.12%

Looks like BS factored in a 2.63% loss of boil off.

I consistently boil off one gallon/hour regardless of starting volume.

Boil off rate should be about the same. BOIL OVER rate may go up.....

David

I will have 25% headspace in the kettle and have the option of using fermcap, boil over rate will be minimal at best

hukdizzle said:

This is exactly what I am talking about. I am thinking that the boil off rate will be slightly lower due to the fact that the liquid will not boil as vigorously being larger. This is the same exact kettle and setup I use for 5.5 gal batches.

Click to expand...

Not sure, but it sounds like you're missing the point that is being made here. The boil off rate in BeerSmith is useless. Boil off has to be measured in gallons per hour, not a percentage of the volume. If you boil off 1-1/2 gallon with a five gallon batch, you'll boil off 1-1/2 gallons with a ten gallon batch. That means that the percentage you use in BeerSmith will be about half. Adjust that percentage number until it gives you the same volume boiled off as you get with a five gallon batch.

This is assuming a constant intensity of boil and you'll have to apply more heat to the larger batch to achieve that. But from the sound of it you may be boiling a bit too hard as is. You're not just going full bore with your burner, are you?

The "boil off %" thing just needs to die. It's flat-out wrong, yet it keeps getting perpetuated in calculators like Beer Smith.

Every system is different - even with the same size kettle. Hell, even location (altitude) makes a big difference. Only way to accurately determine YOUR gal/hr boil off rate is to test it.

AnOldUR said:

Not sure, but it sounds like you're missing the point that is being made here. The boil off rate in BeerSmith is useless. Boil off has to be measured in gallons per hour, not a percentage of the volume. If you boil off 1-1/2 gallon with a five gallon batch, you'll boil off 1-1/2 gallons with a ten gallon batch. That means that the percentage you use in BeerSmith will be about half. Adjust that percentage number until it gives you the same volume boiled off as you get with a five gallon batch.

This is assuming a constant intensity of boil and you'll have to apply more heat to the larger batch to achieve that. But from the sound of it you may be boiling a bit too hard as is. You're not just going full bore with your burner, are you?

Click to expand...

Makes complete sense now, thanks for that I am hard headed haha.

I am running my boils all out which is more than likely a waste of propane but I did it to have a constant output of heat/propane.

hukdizzle said:

I am running my boils all out which is more than likely a waste of propane but I did it to have a constant output of heat/propane.

Click to expand...

I'm a fan of a good rolling boil, but don't go crazy. I have a Bayou SQ14 and a 15 gallon pot. Even when boiling 10+ gallons, I will back off the heat once hot break is achieved.