Hi All.

I have a small bit of info from tonights brew and have questions I'm hoping help clarify using BIABacus. In short I hit my numbers but I'm not sure why!?!

My setup: picobrew RIMS e-biab. I decided to brew http://www.homebrewtalk.com/f69/my-2-ti" onclick="window.open(this.href);return false; ... ipa-81478/ but without the wheat because I forgot to add it.

I have measured my bayou classic and verified my height to cm is pretty accurate to quickly drop in the metal meter stick for water volume. For 60qt I use 39.4 cm diameter, with 0.20 kettle shape heigh adjustment.

I put in a boil-off rate of 5.8 L/hr based on measurement and past brews (this may need to be slightly tweaked but should be close now)

I set desired OG of 1.065 and oddly, it scaled back the numbers from the recipe a tiny bit (e.g. the 2row went from 5216g as prescribed by the recipe to 4990g) etc.

I set my desired volume to fermenter to 5.2 gallon for a 5 gallon batch (is this a safe assumption?)

Question1: Why would my grain bill be reduced? especially where I am missing 0.25lb of wheat from the recipe.Is the reduction because it assume my efficiency is greater than why the recipe was posted with?

I measured my OG at end of mash but I was using a plastic cylinder that was not willing to cool down. I measured the gravity at 1.24 @ 150F. I understand these temp calculations are way off so this number is probably somewhat useless at this temperature. I tried running cold water but the plastic just doesn't conduct well enough (I'm considering a digital pen refractometer to do this accurately)

Next after mahout, I measured the volume into boil after removing the steam basket + bag at 24.4cm = 29.75L

Interestingly my OG after coming out of the plate chiller hit exactly 1.065 as the recipe intended despite missing 0.25lb of wheat.

Question2: To compute efficiency into boil, I think I'd need to cool down the wort to room temp right? the online calculator for ATC for a hydrometer calibrated to 60F (as indicated on the unit) at 150 puts my 1.024 SG @150F at 1.042. This makes my actual EIB at 66.7% instead of the expected 79%.

My EAW expected is 90% and actual is 76.2%. From talking to the owner of this system, 76% would line up with the actual brewhouse efficiency.

I didn't measure the actual VIF because I didn't calibrate any way of doing this and don't like messing with things post-boil. I may try it as an exercise in the future.

Question3: If my EIB, and EAW are so much lower than estimated efficiencies why did I hit my target OG of 1.065 exactly with a sample of cooled wort from the fermenter?

Other most likely irrelevant info:
1. I'm using a hop spider (stainless steel filter) so I put hopsack: y with pull @ <end of boil time>
2. I set KFL to 0.25L as a guess since I don't lost much wort into the fermenter. Maybe this should be 0. Otherwise this number include the losses from pouring out the hops in the spider? which wouldn't make sense because the value would be dependant on the recipe and amount of hops.

Cheers All!