Low partial mash efficiency...CONFUSED!

Hey all, I've done these partial mash/biab recipes a few times now... And last night was the second time my OG was far below my target. I guess I should explain my process first which, I'm sure is messed up somewhere. First thing I do is hop on beer calculus and make a recipe, last night was an ipa

6lb American two-row pale
3lb briess amber DME
1lb crystal 60L
8oz briess carapils
8oz grambinus honey malt

I heated 2.5 gallons to 169° in a 5 gallon pot with a grain bag, mixed in the grain (which was at 66°) and pulled a temp of 154°. Mashed for an hour. I sparged by pouring another 1.25 gallons of water at 170° over the grain, one quart at a time. After mashing and sparging I just move the wort directly over heat to begin my boil... I added the DME at the beginning of the boil. After boiling and cooling I pour my entire batch through a strainer into the fermenter. This is always a tedious process of clogging the stainer and shaking the liquid through, then throwing away the remaining trub on the strainer....over and over and over. Anyways, I add clean water to my fermenter to bring my volume up to 5 gallons. My OG was 1.056. According to my recipe on beer calculus I was supposed to be at 1.069. Any ideas as to why this happened? I've brewed this same way and hit the OG on the head several times. Is my process flawed? It's frustrating not understanding the WHY when this happens.

Thanks for any insights!
Eric

Did you mix in the top off water really well? Often this the cause of a reading that far off target.

beergolf said:

Did you mix in the top off water really well? Often this the cause of a reading that far off target.

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Yeah, I actually went in for a second reading fearing that it wasn't mixed well enough.... Shook the hell out of the fermentor for a couple minutes and took a second reading with the same results

I always mash with 1.25 Qts. per lb. of grain and sparge with 2 Qts. per lb. of grain and get 80% eff. every time. It is a lot of water that has to be boiled off, but it is the only way to get the points you want.

Better luck next time. Enjoy

MBTB said:

I always mash with 1.25 Qts. per lb. of grain and sparge with 2 Qts. per lb. of grain and get 80% eff. every time. It is a lot of water that has to be boiled off, but it is the only way to get the points you want.

Better luck next time. Enjoy

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Yeah I dunno, I've got a 5 gallon brew kettle.. . Working with what I've got. Trying to figure why it would work sometimes and not others.