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Boil Off rate of Kegs

Rep

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Hi
I am recalculating my BeerSmith settings as I have changed my system a great deal.  When I calculate my boil off I used the formula found here: 
http://beersmith.com/equipment_setup.htm

I started with 20 qts. of water, boiled it for an hour and ended up with 15 qts.  Using this formula:  Evap_rate = 100 * (volume_at_start - volume_at_end)/ (volume_at_end) I come up with a boil of rate of 33%.  That seems way too high.  Anybody have any idea on this?
 

Wastegate

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That is what the math says. High, but not unheard of. If it sounds wrong to you do the test again. If you get the same results, then it is correct.

Cheers
Preston
 

Rep

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UselessBrewing said:
That is what the math says. High, but not unheard of. If it sounds wrong to you do the test again. If you get the same results, then it is correct.

Cheers
Preston

Hi Preston
Thanks.  I saw you on earlier and was hoping you would show up in this thread.

After I drafted my OP I did fire up the system.  Last night I boiled five gallons for one hour and boiled off, yup, five quarts.

This morning I visited Home Brew Talk and found the following thread:  http://www.homebrewtalk.com/f84/beersmith-boil-off-106505/

I read a number of posts well into page two and came across what may be a solution.  Let me know what you think.

I opened the Equipment settings in BeerSmith and then the setting I am working on.  I set it for five Gallons. 

Then, where I had set up my, "Evaporation Rate (5-15%) to 33% I began to move that figure downward.  Each new figure provided me a new value in the, "Boil Off" setting that sits to the right of the, "Evaporation Rate (5-15%)" setting.

Eventually I struck an evaporation rate of 18.9% that gives me a boil off of 1.25 gallons an hour.

So, my evaporation rate is not 33% but rather 18.9% per hour.  And, as long as I recalculate my final boil volume correctly this should work for me.

Am I correct or, am I missing something?
 

MaltLicker

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I would think the calc would be the loss over the original, so 5/20, or 25%.  If you'd started with 100, you'd end up with 75, right?  or 75% left, so you lost 25%?  Still seems high.  Were you really flaming it?
 

Rep

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MaltLicker said:
I would think the calc would be the loss over the original, so 5/20, or 25%.  If you'd started with 100, you'd end up with 75, right?  or 75% left, so you lost 25%?   Still seems high.  Were you really flaming it?

The BeerSmith calculation does give 33% using the 20 grt start and 15 qrt finish.

I am using Hurricane burners for natural gas.  I moved from a gravity fed propane system to a single tier natural gas.  Thus, it was a good time to tweak BeerSmith a bit. 



 

Wastegate

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Well! That brings up the need to check my volumes on 11G batches...

I read all 3 pages, Good find!

Cheers
Preston
 

Rep

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UselessBrewing said:
Well! That brings up the need to check my volumes on 11G batches...

I read all 3 pages, Good find!

Cheers
Preston

It was/is a good read.

Therefore, am I right in using 18.9%?  I will be brewing in teh morning and can use your opinion.
 

MaltLicker

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Rep - Yes, from reading that other forum thread, I think isolating YOUR loss amount is more accurate (or transferable?) than using a percentage.  Percentages seem unreliable b/c you cannot take them from one batch size to another. 

But I'm still confused on the math.  If the price of a brew pot is $100, and it gets reduced to $75, that is a 25% reduction, correct?  The delta over the original, 25/100, is 25%? 


"The BeerSmith calculation does give 33% using the 20 grt start and 15 qrt finish."

This math would indicate it is putting the 5 qt loss over the finished amount, or 5/15.  That is not the PCTG amount lost from the starting value. 
 

Wastegate

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+1 I agree go with the volume and not the %...

Cheers
Preston
 

Rep

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MaltLicker said:
Rep - Yes, from reading that other forum thread, I think isolating YOUR loss amount is more accurate (or transferable?) than using a percentage.  Percentages seem unreliable b/c you cannot take them from one batch size to another. 

But I'm still confused on the math.  If the price of a brew pot is $100, and it gets reduced to $75, that is a 25% reduction, correct?  The delta over the original, 25/100, is 25%? 


"The BeerSmith calculation does give 33% using the 20 grt start and 15 qrt finish."

This math would indicate it is putting the 5 qt loss over the finished amount, or 5/15.  That is not the PCTG amount lost from the starting value. 

I don't know why Brad uses this formula for calculating Boil off rates, but he does.

Evap_rate = 100 * (volume_at_start - volume_at_end)/ (volume_at_end)

Using my numbers, confirmed by boiling a five gallon batch on two separate days I get the following.

Rep's Evap Rate = 100 * (20qrts at start - 15qrts at end)/(15qrts).

Or, 500 divided by 15 = 33333333% for Rep's Evap Rate.

Thanks Preston and MaltLiker, I appreciate your advice.  Unfortunately I am unable to brew today due to weather so will have to wait til tomorrow.

I have not brewed since July and cannot wait to fire up my new brew stand.  I have spent time testing it, redoing some of it and tweaking other parts of the system and BeerSmith as well.
 

Wastegate

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PIC's and lots of them!  ;D

We all need our Beer Porn fix!

Cheers
Preston
 
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