Why can't I hit my target OG?

[Plan9]

I have a bad track record of my OG ending up about 10 points less than Beersmith is expecting. Even with lowering the efficiency to 65%

I wanted to describe my system and process and see if I can get some advice on what I may be doing wrong, or over looking.

The system is a single tier, 3 keggle electric RIMs with a single pump.
HLT has 240V 4500W element and temp prob in the tee of the site glass.
Boil kettle is similar except 5500W element.
Mash tun has a false bottom and the temp prob is on the end of the RIMS tube. 120V 1500W element in the tube to maintain temp.

I have tried both batch sparging and biab style no sparge. Similar results.

This last batch was 10G IPA.
28lb grain
65% tot efficiency
Target OG 1.066
Mash in 9.75G 162* water and held at 152* for 60min
Drained tun into kettle
Added in 4G 168* water and recirculated for 5-10min
Drained and repeated with 4 more G
Did not take a pre boil gravity, but end of the boil it measured 1.055

I don't believe it is my crush as I milled my neighbors grain for their traditional propane/igloo/fly sparge brew and they hit their mark exactly.

Please ask for any more info. I'd like to see what else to tweak for next time.

Thanks!!

 

[Oginme]

The two things I would look at are as follows:

Mash efficiency -- which is difficult to calculate without pre-boil volume and gravity and any losses to mash tun dead space.

Boil off rate -- again, the pre-boil volume is needed to calculate as well as any post boil losses to trub.

 

[McKnuckle]

You used a lot of water here: 9.75 + 4 + 4 = 17.75 gallons

Assuming normal grain absorption of 0.12 gal/lb, you'd lose 3.36 gallons to the grist. You should collect a pre-boil volume of about 14.39 gallons. Do you lose some volume in the mash tun? Subtract that here if you do.

If you then boil off 1.39 gallons (to make the math neat), you'd have 13 gallons to the fermenter. This is for a 10 gallon batch? Sounds like a lot of excess water.

 

[Plan9]

You have a good point there. It was a very soupy mash and there was wort left over after the carboys had been filled.

Something is probably off in my equipment profile.

Next batch I will do all my math on paper, measure boil off and dead spaces. Then if I see a change I can adjust the software to match my real results.

 

[dmtaylor]

Another thing that might hurt is the intended OG of 1.066. If your average batch is less than this, like 1.060 or whatever, be aware that higher gravity beers will lose a few points of efficiency. So, if you usually get 75% with 1.060, then expect maybe only 70% for a 1.066 beer or whatever.

Also ensure all volume measurements are correct. If you wanted 10 gallons, but instead got 12 gallons out, then of course the dilution to 12 will reduce your intended gravity by a huge amount.

Any or all of these things can be factors in reducing efficiency and gravity. Fix the ones that are broke, and better luck next time. Or actually, it's not luck, it's skill.