BeerSmith: cooling % means what, exactly?

Within “Equipment”, after setting some constants and specifying boil time, Beersmith tells me how much pre-boil wort I need to collect in order to get a specified amount into the fermenter. Lovely. Thanks, Beersmith.

However, I’m wondering why Beersmith recommends I set cooling percentage losses to 4%? If Beersmith is correct here, this number reflects the volume loss between the warm wort collected (but not yet heated for boiling) and the cooled wort dropped into the fermenter. So, I lose 4% volume going from 140 degrees to 68? I’m just guessing on that starting number 140 - I batch sparge with two run-offs, trying to get each run-off close to 170, but surely lose a chunk of that heat in the time it takes. But that's the point, b/c shouldn't our % loss be based on the temperature swing in question? One man's pre-boil wort temp is not the same as another's. And if we're cooling down to 48F for a lager, well, shouldn't that cooling % loss number be even higher?

I always presumed that 4% standard loss was a measure from boiling wort to room temp wort. (Which I figure isn’t really a loss at all, since there’s first expansion followed by contraction.) Beersmith seems to be telling me otherwise, yet not telling me enough.

That 4% only reflects a quarter gallon loss, so it’s not totally critical, but then again who of us likes to pour 2 pints of homebrew down the toilet? Or 2 pints of flat, warm brew down our throats because they won’t fit in the keg? Not as bad, granted, but still…

Am I getting something wrong here? What exactly does that 4% account for?

I have alway understood this to be post boil volume minus post cooling volume coverted to equal percentage.

It's uses to calculate total volume to account for cooling losses so you have your target volume available to ferment.

GilaMinumBeer said:

I have alway understood this to be post boil volume minus post cooling volume coverted to equal percentage.

It's uses to calculate total volume to account for cooling losses so you have your target volume available to ferment.

Click to expand...

I see.

I still don’t see, though. Why would that amount need to be factored in to calculate pre-boil volume? It’s not really a ‘loss’. Working backwards from, say, 5.5 gallons into the fermenter… you need 5.5g plus trub loss, plus shrinkage loss at end-of-boil (pre-cooling). But then working all the way back to wort collection (pre-boil volume) aren’t you going to gain back that loss to shrinkage?

Target fermenter volume (cooled wort) = 5.5
Target end of boil volume (boiling wort) = 5.5 + loss to trub + loss to shrinkage
Target start of boil volume (boiling wort) = 5.5 + loss to trub + loss to shrinkage + loss to evaporation
Target pre-boil volume (~warm wort) = 5.5 + loss to trub + loss to shrinkage + loss to evaporation + (- some loss to shrinkage)

Argh. I’m suffering some shrinkage of my own here. Does 4% account for ‘partial’ shrinkage?

You factor your total water volumes into the boiler so that once the trub is formed, eveporation complete, and shrikage of volume your target gravities don't get skewed by topping off.

Most, care only for gravity into the fermenter but sveral have some severe hemmorages if they drain their kettles only to find they have 5 gallons going in then considering losses to yeast they have 4.5 going into packaging.

At that point if you top off, you dilute.

some just obsess about hitting the numbers and wouldn;t dare consider leaving a half gallon of fermented wort behind.