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Shouldn't Est OG be based on post boil volume and not batch size?

McCue

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I lose about 1 gal in my kettle so my post boil volume is 6 gallons in order to collect a 5 gallon batch in the fermenter.  So shouldn't my Est. OG be calculated with 6 gallons and not the batch size which specifically says it's measured into the fermenter?  It looks to me like it's using the batch size.  For example if I do a new recipe with a single ingredient of 6 lbs pale liquid extract (36 ppg) and I'm going to boil it down to a post boil volume of 6 gallons the OG should be 1.036.  That’s what the software gives me if I set the Batch size at 6 gallons but If I set it to 5 which is actually my batch size it gives OG=1.043.  I assume I'm doing something wrong, but can't figure it out.  What's the correct way to do this?
 
Batch size is the final volume of cooled wort.  That is what you made and that volume accounts for all sugars created and water added or boiled off.  When you change batch size to five, it correctly assumes you boiled off a gallon and that further concentrated the wort to 1.043. 

Your first comment "I lose about 1 gal in my kettle so my post boil volume is 6 gallons in order to collect a 5 gallon batch in the fermenter."

Do you mean pre-boil of seven, boil to six, and collect only five?  Or do you mean PRE-boil six, boil off one, five remaining for fermenter? 
 
I start with 7 gallons and boil down to 6.  Based on the height of the valve coming out of my kettle and not wanting to disturb the settled out break material I leave a gallon behind and only transfer 5 gallons to the fermenter.

So you're saying that BeerSmith assumes that you empty the entire boil kettle into the fermenter with no losses?  That seems odd considering how many ways it gives to you account for losses in other parts of the process.  For example under the water volume tab it assumes that your "batch size" all goes into the fermenter but then lets you subtract bottling and fermentation loss to get an accurate bottling volume.
 
For your scenario, I think you need to set your trub and chiller loss to 1 gallon in the equipment profile.
 
I am having the same problem.  I have about 1.25 gal of losses between my boil kettle and the fermentor.  If I select a batch size of 10.5 gal into the fermentor, BeerSmith2 gives me a PRE-boil volume of 14.3 gallons and a POST-boil volume of 12.2 gal (which works, 2.1 gal in evaporation; 14.3 - 2.1 = 12.2).

For a recipe with a OG of 1.045 with 100% pale malt (36 GU/lb), BeerSmith2 calculates 17.5 lbs of malt.  However, if you do the math 17.5 lbs of pale malt will yield an OG of 1.045 for a 10.5 gal POST-boil volume, not a 12.2 gal POST-boil volume.

Assume 75% efficiency:

45 GU * 10.5 gal = 472.5 total GU
472.5 /36/.75 = 17.5 lbs pale malt

45 GU * 12.2 gal = 549 total GU
549/36/.75 = 20.3 lbs pale malt

In order to hit an OG of 1.045 with a POST-Boil volume of 12.2 (in order to get a batch volume in the fermentor of 10.5 gal) I need 20.3 lbs of malt.  BeerSmith2 is telling me I need 17.5 lbs.

This explains why I haven't been able to hit an accurate OG.  Is there something I'm doing wrong??
 
McCue said:
I start with 7 gallons and boil down to 6.  Based on the height of the valve coming out of my kettle and not wanting to disturb the settled out break material I leave a gallon behind and only transfer 5 gallons to the fermenter.

So you're saying that BeerSmith assumes that you empty the entire boil kettle into the fermenter with no losses?  That seems odd considering how many ways it gives to you account for losses in other parts of the process.  For example under the water volume tab it assumes that your "batch size" all goes into the fermenter but then lets you subtract bottling and fermentation loss to get an accurate bottling volume.

I do almost the same thing to keep my wort clear into fermenter.  But some people dump the whole pot thru a funnel, so zero fluid losses.  Rivercity is correct; whatever you choose to lose should be entered as loss.
 
MaltLicker said:
McCue said:
I start with 7 gallons and boil down to 6.  Based on the height of the valve coming out of my kettle and not wanting to disturb the settled out break material I leave a gallon behind and only transfer 5 gallons to the fermenter.

So you're saying that BeerSmith assumes that you empty the entire boil kettle into the fermenter with no losses?  That seems odd considering how many ways it gives to you account for losses in other parts of the process.  For example under the water volume tab it assumes that your "batch size" all goes into the fermenter but then lets you subtract bottling and fermentation loss to get an accurate bottling volume.

I do almost the same thing to keep my wort clear into fermenter.  But some people dump the whole pot thru a funnel, so zero fluid losses.  Rivercity is correct; whatever you choose to lose should be entered as loss.


That still doesn't change the fact that the grain bill is being calculated based on the volume into the fermentor not the volume in the boil kettle.  Addin the losses will make the OG calculationeven farther off by causing BeerSmith2 to increase the volume in teh BK to compensate for the loss.
 
rosenjm said:
I have about 1.25 gal of losses between my boil kettle and the fermentor.  

If I select a batch size of 10.5 gal into the fermentor, BeerSmith2 gives me a PRE-boil volume of 14.3 gallons and a POST-boil volume of 12.2 gal (which works, 2.1 gal in evaporation; 14.3 - 2.1 = 12.2).  

Is your 1.25 gallon loss entered?  Adding up your needs, I get 10.5 + 2.1 evaporation + 1.25 lost = 13.85 gallons (ignoring cooling loss)

13.85 ga * 45 GU = 623.25
623.25/36/.75 = 23.08 lbs malt

But this assumes you need to generate 13.85 gallons of gravity 1.045 when you don't really.  The 2.1 evaporation takes away volume but leaves SG, giving you GU that you don't have to get from the grain bill, right?  So whatever PPG you gain from 2.1 gallons evap saves you that much grain.  [Black box math, I presume.]

But the 1.25 loss must be accounted for since those GU from grain do not contribute to SG.  

 
Yes, my losses are properly entered.  I don't have an issue with the way BS2 is calculating water volumes.  The issue is it is using the wrong volume to calculate gravity and subsequently the grain bill.

This is really hard to explain in this format, but here goes...

For my set up, if I want 10.5 gal in the fermentor, i need 12.2 gal AFTER the boil (12.2 - .49 gal [4% cooling loss] - 1.25 gal trub and chiller = 10.46 gal).  OG is taken in the fermentor, therefore the gravity in the fermentor is equal to the gravity in the boiler POST boil.  The cooling losses and the trub and chiller losses revome volume, NOT gravity.  If I want 1.045 in teh fermentor, then the gravity of the 12.2 gal in the boiler POST boil will also be 1.045. 

The 2.1 gal loss due to evaporation during the boil concentrates the sugar (water is boiling avay, not sugar), therefore PRE boil the gravity will be lower than 1.045.  [(GU pre boil x Vol preboil)/Vol post boil = GU post boil].

GU pre boil = [(45 * 12.2)/14.3] {12.2 + 2.1 evap = 14.3 gal pre boil volume}
GU pre boil = 38

Total gravity units and not affected by boiling or dilution, it is a measure of the sugars present. So back to our example, if I want 12.2 gal of wort at 1.045:


45GU * 12.2 = 549 total gravity units
549/36/.75 = 20.3 lbs

or if you want to look at the PRE boil values:

38GU * 14.3 = 543.4
543.4/36/.75 = 20.1 lbs

The differences can be accounted for in my rounding.  Regardless, the total gravity units are unaffected by boiling.

The bottom line is this;  Beer Smith is calculating the grain bill based on the volume in the fermentor NOT the volume in the boiler. ((45 * 10.5 gal))/36/.75 = 17.5 lbs. It is NOT taking into account the losses after the boil. i.e if I tell BS2 I want a OG of 1.045 it is going to tell me to use 17.5 lbs of pale malt.  If I do, I'm going to get 1.039:

17.5 lbs * (36 * .75) = 472.5 total GU
472.5/12.2 gal = 38.7

The cooling losses and the trub and chiller losses DO NOT affect gravity, they are simply losses of volume.  Whatever the gravity of the wort is in the boiler at the end of the boil is what the gravity will be in the fermentor and therefore measured OG.  The software is not calculating it correctly.
 
I believe I see the same issue, but can give a different view of it that might be a little more descriptive of the problem (hopefully).  The thread exists on HBT (http://www.homebrewtalk.com/f36/steeping-grains-adding-gravity-294583/#post3663000), but I'll cut / paste it below.

-------------------------
mmonacel 01-13-2012 09:56 PM
Steeping grains adding gravity?

I'm looking to do an all-grain Janet's Brown from JZ's BCS book (page 143). Below is the grist. Everything but the 2-row and Wheat Malt are listed as "steeping grains". I plan to mash them like I always do. The books lists the OG as 1.066, but BeerSmith and my own calcs show 1.074. Now if I exclude the steeping grains from the gravity contribution calculation it comes to 61, which is closer, but still a bit off. All ppp/gal figures are from BeerSmith. Where am I going wrong here?
Code:
Grain                ppp/gal      pounds      Gravity Contribution
2-row                        37            12            56.51
Wheat Malt        40            1              5.09
Cara-Pils            33            1.25          5.25
Caramel 40        34            1.25          5.41
Chocolate 420    35            0.5            2.23
                     
gallons        5.5             
efficiency        0.7             
Total Gravity Points        74.49

mmonacel 01-13-2012 10:00 PM
sorry - above was the best table-like formatting I could do

jdrowell15 01-13-2012 10:06 PM
Does your efficiency in Beersmith match the recipe?

mmonacel 01-13-2012 10:29 PM
Yes - all the BCS recipes are set to 70% and BeerSmith is also set to 70%. Since my calcs and BeerSmith's calcs come out the same I think the entry is good.

jdrowell15 01-13-2012 10:34 PM
I remember BCS does extract first and then tells you what grains to replace the extract with. Maybe they give the gravity for if it was brewed extract and not all grain. When you brew extract you are not converting the specialty grains to sugar where as you are in all grain. That could account for the little difference you are seeing.

jdrowell15 01-13-2012 10:36 PM
Steeping grains and specialty grains are typically one in the same. Though not always.

mmonacel 01-13-2012 11:27 PM
I think I found it... It appears to be an issue with batch size.

My "batch size" figure in BeerSmith is set to 5.5 gallons. This is because BS defines "batch size" as what goes into the fermenter. You can see this in the Classic Recipe view where it shows "Batch Size (fermenter)" as well as the help files. In BCS all recipes are 6 gallon recipes and assumes .5 gal loss to trub and chiller (ie. 5.5 into fermenter for 6 gallon recipe) and .5 gal fermenter loss (which equates to 5 gallon bottling). This is also how my equipment profile is set up.

Unfortunately if you enter in a 5.5 gallon batch size for the recipe, all the volumes work out (volume into fermenter and bottling volume) but the gravity contributions do not. If I put 6 gallons in for a batch size, my gravity contributions work out (in this case they come to 68 which is almost spot on) but the fermenter and bottling volumes are .5 gallons off.

Hmmmm... is this a bug in BeerSmith or am I thinking about this the wrong way?

mmonacel 01-13-2012 11:29 PM
Maybe the "bug" is simply the display of "Batch Size (fermenter)" in the classic view not taking into account the chiller / trub loss...
 
For those interested in the answer / reason, see these links. In short, BeerSmith treats trub / chiller losses different than some would expect.

http://www.thebrewingnetwork.com/forum/viewtopic.php?f=2&t=17961&start=0

http://www.homebrewtalk.com/f12/janets-brown-beersmith-vs-classic-styles-258275/

I set the batch size to 6 gallons and my trub/chiller losses in my equipment to 0 and not only are the gravities correct, but the water/liquid volumes match up much closer to reality.
 
Based on the height of the valve coming out of my kettle and not wanting to disturb the settled out break material I leave a gallon behind and only transfer 5 gallons to the fermenter.

That's like tossing every sixth batch.

I suggest you try making two batches following the same recipe, one the way you usually do it and another without discarding the break material.

I would be surprised if you find a perceptible difference between the two.
 
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