Author Topic: Water & Gravity calcs don't seem to work right  (Read 3645 times)

Offline JoePerri

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Water & Gravity calcs don't seem to work right
« on: November 01, 2008, 01:48:59 PM »
Hi All,

Perhaps I'm not the sharpest knife in the drawer or I'm missing something obvious but the water and gravity calculations don't seem to work properly. It seems the OG calculation is only related to grist bill & "Batch Size" field. Nothing else changes it. This is a problem. I'll give a simple example. Lets say I want to collect 5 gallons of 1.040 wort into my fermentor. One would think that I should set my batch size to 5 gallons and add grains to hit 1.040 based on my brewhouse efficiency. But I also need to keep in mind the amount of water needed and wort lost elsewhere in the process. BS provides a handy tool to calculate and keep track of all these issues, boil-off, deadspace, etc. My kettle holds about .75 gal of lost wort in the trub and dead space. If I set this value to .75 in BS it correctly back-calculates the water needed at the start of the boil. HOWEVER it does not change the OG to reflect the truth that I am now brewing 5.75 gallons of wort! A simple experiment will show this and why it is wrong. Go into BS and set the "Lost to Boil Trub & Chiller" value to 10 gallons. You are now making 15 gallons of beer with the same amount of grain yet the OG does not change! In my set up I really do need to end up with 5.75 gallons of wort to get 5 gallons into the fermentor. Of course I can just change the batch size to 5.75 gallons and set the trub/chiller loss to 0 and get the right OG but that is counterintuitive and makes the trub/chiller loss field useless. There are other fields that behave in the same way. Of course the efficiency calcs are completely wrong in all cases because they take none of these losses into effect. Am I missing something here?

Thanks,
joe

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Re: Water & Gravity calcs don't seem to work right
« Reply #1 on: November 02, 2008, 09:46:35 PM »
Joe,
  Brewhouse efficiency includes all losses in your brewing system - it is a gross number that includes losses for boiling, trub, deadspace, etc....  Here's an article on it:
   http://www.beersmith.com/blog/2008/10/26/brewhouse-efficiency-for-all-grain-beer-brewing/

Cheers,
Brad
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Offline JoePerri

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Re: Water & Gravity calcs don't seem to work right
« Reply #2 on: November 03, 2008, 12:26:10 PM »
Hi Brad,

Thanks for the reply. A couple of points:

1. Could you address my original questions? Namely that the OG and water calcs don't work properly. It really is a problem.

2. I understand brewhouse efficiency but Beersmith does not calculate it properly for the same reason that the OG is not calculated properly. I will give you an example. Suppose a brewer wants to brew 5 gallons of a 1.039 wort with an efficiency of 70%. He puts the proper numbers into beersmith including his .75 gallons lost to trub/kettle. Since beersmith does not take this extra volume of wort into consideration it thinks he should end up with 5 gallons at 1.039. Our brewer actually measures 1.034 into the fermentor and runs the brewhouse efficiency tool. It tells him that his efficiency is only 61%! This is because he actually made 5.75 gallons of wort, not 5 gallons. But his OG IS the right number and his efficiency really is 70%. The grist bill will give an OG of 1.039 for 5 gallons at 70% OR 1.034 for 5.75 gallons at 70%. Of course if our brewer knows that beersmith does not calculate certain things properly and if he does not follow the help files which tell him to enter the exact volume into the fermentor, he can figure out his losses to trub/deadspace/hoses etc. and enter that number into the field reserved for volume into the fermentor and get the right number. But again this makes no sense as the purpose of brewing software is to keep track of these things correctly and do the calcs properly. Does this make sense?

Thanks,
Joe