Bad Math: Loss to Trub and Chiller

Brad and other advanced users, please check my results to make sure I didn't overlook something.

One lb of sugar as 1 gallon of wort should yield an OG of 1.046. This 1:1 ratio locks in a total number of gravity points for any volume. Thus, a 1:0.5 ratio should yield 1.092, while a 1:2 ratio should yield 1.023. Aside from preboil predictions, which I noted in another post, this matches BeerSmith's predictions with no boil off, trub or top up water.

The following recipe maintains a 1:1 ratio, but places 10% of the wort into trub loss (50 gal trub + 450 yield = 500 ttl). The result is a yield of 1.051, which exceeds the capability of straight sugar. This 11% rise seems steeper than straight linear. Doubling trub loss results in an even higher gravity than expected.

Hi,
  Similar to the other post you posted, you again used an "all grain" example with no grains in it, except for a single "sugar" marked as type "grain".  The problem with this is when you have a "sugar" marked as a "grain" in an all grain recipe, then BeerSmith will apply the brewhouse efficiency to it, resulting in a lower original gravity as grain that is mashed does not yield the same as sugar.  Remember also that for an all grain recipe, the brewhouse efficiency INCLUDES all losses including the trub loss.  So in your example you are saying you achieve 100% brewhouse efficiency even though you have the trub loss (thus the violation of physics in the example).

  To make a clean example, you need to change the type of your sugar to "sugar" and not "grain", and change the type to "Extract" since you are not using any grains.  This will result in the correct value of 1.046.  Conversely if you want to keep the example all grain for some reason, you would need to lower the brewhouse efficiency from the 100% number to account for the trub loss (by definition, brewhouse efficiency includes trub loss), which would again give a correct value.

Brad

Hi,

I understand that trub loss is used in the calculation for BHE, but it seems to be subtracted from the volume that specific gravities are calculated on rather than added. Am I wrong in thinking this way?

A quick example of why I feel this way...

If I start with the volume I wish to get into my fermenter (let's say 5.5 gallons), place a value of 0.5 gallons in the trub loss field, know what my boil off is for 60 minutes (let's say 2 gallons for simplification), then I should have a pre-boil volume of 5.5 + 0.5 + 2 or 8 gallons.  (Let's leave expansion out for this example).

After boiling for 60 minutes, I should have 6 gallons in my BK.  If I look at my recipe, my OG is based on the 5.5 gallons, not the total 6 gallons that are in the BK. (for example, my recipe shows an OG value of 1.050).  I can prove this by setting my batch size to 6 gallons, and my trub loss to 0...which will give me an OG based on the total volume in the BK (for argument sake let's say that this value is 1.046).

The OG of what is in the trub will have the same OG as that of the wort that is moved into the fermenter, since it is all part of the total volume in the BK.  It appears that adding a value to the trub loss field is acting as if the volume is being reduced by boil off (concentrating the liquid) rather than being viewed as part of the total volume.

I hate to beat a dead horse, but I've seen this being brought up in multiple discussions.  I understand that I can tweak my BHE to get my numbers correct...but if it's a matter of inverting how the value of the trub loss is used in the equation (adding it rather than subtracting it), shouldn't the fix be made in the software?

Thanks for listening.

-Dan

Are we anywhere near agreeing on this and resolving it? I'm unsure what to do now.

Brad?

Cheers all and hear's to a fantastic year of brewing.

Simon

I'm doing more work on the subject. I am trying to isolate the individual variables that create the errors. Hopefully, if I'm more specific, then Brad can address it more efficiently.

Brewhouse efficiency is simply the percentage total sugars available that actually get into the fermenter. Here is a working calculation for BHE. It's simple and direct and will get you into the ballpark for BeerSmith predictions.

BHE = (Sg x BV) / (Pg x GW)

BHE: Brew House Efficiency
Sg: Wort Specific Gravity, post chill (or post boil)
BV: Batch Volume, as measured in the fermenter
Pg: Potential gravity of grain (found by double clicking the ingredient, but 39 is a good starting number)
GW: Grain Weight

This formula simply divides the gravity points yielded into the fermenter by the total gravity point potential of grain (or extract or sugars) used.

As with all gravity calculations, the specific gravity 1.0 is dropped (1.040 becomes 40).

The predicted gravity and trub issue has really been bugging me so I have been trying to reverse engineer the calculations. Many spreadsheets later I feel I understand it.  Lets simplify as much as possible.
Create a new recipe
Set recipe type to ‘extract’.  This removes the efficiency variables.
Set the batch size to 5gal(20qt)
Add 5 lbs of sucrose (1.046ppg)
Zero out all your losses in the equipment profile and volumes tab (shrinkage, boil off, trub, mash, fermenter, etc)
Uncheck ‘calc boil vol’ option
Set the Estimated Pre-Boil Vol (EPBV) to 0

You should have an Est Original Gravity (EOG) of 1.046.

Now set your trub to 1gal.  What happened to the EOG?  It went down to 1.038.  This is correct because your batch size didn’t change.  BeerSmith calculates the original volume of water needed based on the batch size and the trub loss.  Everything is reference to the batch size.  You have to mix the sugar with more water to get the same batch size because of the trub loss (which reduces the gravity).

So if you now change your batch size to 4gal the EOG will be back at 1.046. Here is the math to back it up.

With no losses the pre-boil vol = post-boil vol = batch size
Total extract = 46ppg X 5lbs = 230
Gravity = extract / vol
Vol = batch size + trub

In the first case the vol = 5 + 0 = 5
So the gravity = 230 / 5 = 46  (1.046) 

After the trub is changed the vol = 5 + 1 = 6
Gravity = 230 / 6 = 38 (1.038)

Adjusting the batch size down to compensate gives a vol = 4 + 1 = 5
And the gravity = 230 / 5 = 46 (1.046)

Now you can add back your other losses but you will find that none of the other losses have any impact on the EOG because it is a function ONLY of total extract / (batch size + trub.)

Now if you doing this in an ‘all grain’ recipe that uses efficiencies it gets a little more complicated.  Using drb1215’s example from above

drb1215 said:

I can prove this by setting my batch size to 6 gallons, and my trub loss to 0...which will give me an OG based on the total volume in the BK

Click to expand...

This would also change your Est Mash Eff.  (Actually it should change the Tot Efficiency but since it is a fixed number, it adjusts the Est Mash Eff respectively.) You would need to change the Tot Efficiency to adjust the Est Mash Eff back to where it was before you changed the trub value. 

Everything is tied to the batch size and the trub.  If you change the batch size or the trub that will change your Est mash Eff which will change your extract.  You need to adjust the Tot Efficiency to get your desired Est Mash Eff.  That is why it would be great to have the Mash Eff as a settable value and have the Tot Eff calculated.  I think it would clear up so much confusion.

As far as I can tell this is working as designed and is not a bug.  Having said that, I found that there is something very strange with the Est Pre-Boil Gravity, but I will leave that for another post.

In my last post http://www.beersmith.com/forum/index.php/topic,9665.msg41575.html#msg41575 I explained how the Est Original Gravity really works.  I also mentioned that I found something screwy with the Est Pre-Boil Gravity.  Let’s return to my test recipe with no losses. Here it is again if you don’t already have it built.
Create a new recipe
Set recipe type to ‘extract’.  This removes the efficiency variables.
Set the batch size to 5gal(20qt)
Add 5 lbs of sucrose (1.046ppg)
Zero out all your losses in the equipment profile and volumes tab (shrinkage, boil off, trub, mash, fermenter, etc)
Uncheck ‘calc boil vol’ option
Set the Estimated Pre-Boil Vol (EPBV) to 5gal (this is different from the previous example)

You should have an Est Original Gravity (EOG) of 1.046
You should also have an Est Pre-Boil Gravity (EPBG) of 1.046.  No losses remember.

Now change the trub to 1gal.  The EPBG jumps to 1.055.  Huh?  That is higher than the potential extract of sugar! Oh, I know, we forgot to change the Batch Size to compensate for the trub.  Set the batch size to 4gal and check your EPBG.  Surprise! The EPBG actually went up to 1.058.

Well after many sleepless nights, spreadsheets with pretty graphs, and several pints of homebrew, I cracked to mystery.  The key is that Tot Efficiency is locked to 100% in extract mode.  However, when you change the trub the Est Mash Eff changes and you need to change the Tot Efficiency to compensate.  But since the Tot Efficiency is locked we get stuck with a higher Est Mash Eff. This is how you end up with a higher EPBG than possible because it is using an Est Mash Eff > 100%. 

You may be saying “but the efficiencies are not used it extract mode” and that “efficiency shouldn’t be applied to sugar in the first place.”  You are correct and I would call those two issues bugs!

You can see this in action if you change the recipe around a bit.
Set to “All Grain”.
Batch Size = 5
Trub = 0
EPBV = 5
Tot Efficiency = 100
Delete the sugar and add 5lbs of Pale Malt (2 Row) US and set the extract to 1.046 for this example. (This is just to help compare to the numbers above)
You have to toggle to another tab and back to the design tab in order to see the updates.

You should have EOG = 1.046 and EPBG = 1.046.  That looks familiar. This is what we were getting in extract mode.  Your Est Mash Eff should be 100%, the same as your Tot Efficiency.

Now change the trub to 1gal.
Toggle the screen to update and look at your EPBG, 1.055. This is higher than possible from the grain.  Look at your Est Mash Eff.  Ah ha!  120%.

Now change the Batch Size to 4gal and toggle to update. Now the EPBV = 1.058 and the Est Mash Eff is 125%.

Change the Tot Efficiency to 80% and toggle to update.  The Est Mash Eff should now be 100% and your EPBG and EOG are both 1.046 which is correct.

Conclusion #1:  Make sure you always adjust your Tot Efficiency to get the desired Est Mash Eff when you adjust ANY of your volumes.
Conclusion #2:  There is a bug where sugar is being affected by the Est Mash Eff.  I checked and my sucrose is set as sugar and not grain.
Conclusion #3:  There is a bug were the Est Mash Eff is being applied in Extract mode.
Conclusion #4:  Making Mash Eff the settable value and having the Tot Efficiency calculated would fix a lot of this stuff and eliminate a lot of confusion.  Everything keys off the Mash Eff anyway.  Every time you change anything you have to change the Tot Eff to restore the Mash Eff or it throws off all your numbers.  In homebrewing I feel the volumes are more variable than the Mash Eff.

For the record I’m using BeerSmith build 2.2.12 on Windows XP(32).