Relationship between Gravity & Efficiency

[OdeCloner]

I brewed my first lager a few weeks ago, and I hit 93% efficiency on a system that generally produces 83%. I think I understand why, but I wanted to bring this to a larger audience.

Recipe was:
85% Pilsner Malt
14% Munich Malt
1% Melanoiden Malt
Rice Hulls
OG: 1.047

As I began running off, and fly sparging, my first runnings were in the 1.070 range, middle runnings were 1.050, and late runnings were 1.010. On a planned efficiency of 80%, I achieved 93% and overshot my gravity by about 8 points.

I've never sparged down to where my runnings were 1.010 before, and I'm thinking this is the reason for the higher efficiency. Anything over 1.000 represents sugar left in the mash tun, and if I'm rinsing more and more of it off, more is going in the boil kettle and increasing the extraction efficiency.

Conversely, when I've made RISs and my final runnings were at 1.040, I've seen efficiencies in the high 70s. There, again, I'm leaving sugar in the mash tun, which therefore decreases the extraction efficiency.

Of course, extraction efficiency is influenced by many things such as crush, technique, but I conclude also that extraction efficiency is influenced by specific gravity of final runnings. Seems pretty obvious, but I don't hear this community talking about efficiency in this way. Am I thinking about this correctly?

(My setup is a 2 tier, 3 keggle HERMS)

 

[acidrain]

You are thinking correctly as far as pure efficiency is concerned, but don't forget that the lower gravity runnings are actually diluting your overall batch.
If you-re adding 1.010 SG wort to a batch that is scheduled to be a 1.040 pre-boil, it doesn't make sense to keep adding the dilute wort. You'll need to boil it down to achieve the SG you're looking for, and in doing so are darkening the beer and wasting fuel.
You'll need to add more grain, stop running at a higher SG in order to hit the preboil volume and SG.
Why did your system achieve 93% this time? It should be consistent batch-to-batch.

 

[max384]

I brewed my first lager a few weeks ago, and I hit 93% efficiency on a system that generally produces 83%. I think I understand why, but I wanted to bring this to a larger audience.

Recipe was:
85% Pilsner Malt
14% Munich Malt
1% Melanoiden Malt
Rice Hulls
OG: 1.047

As I began running off, and fly sparging, my first runnings were in the 1.070 range, middle runnings were 1.050, and late runnings were 1.010. On a planned efficiency of 80%, I achieved 93% and overshot my gravity by about 8 points.

I've never sparged down to where my runnings were 1.010 before, and I'm thinking this is the reason for the higher efficiency. Anything over 1.000 represents sugar left in the mash tun, and if I'm rinsing more and more of it off, more is going in the boil kettle and increasing the extraction efficiency.

Conversely, when I've made RISs and my final runnings were at 1.040, I've seen efficiencies in the high 70s. There, again, I'm leaving sugar in the mash tun, which therefore decreases the extraction efficiency.

Of course, extraction efficiency is influenced by many things such as crush, technique, but I conclude also that extraction efficiency is influenced by specific gravity of final runnings. Seems pretty obvious, but I don't hear this community talking about efficiency in this way. Am I thinking about this correctly?

(My setup is a 2 tier, 3 keggle HERMS)

You're thinking about it correctly.

We generally talk about either mash efficiency, as opposed to SG of the final runnings, because an efficiency percentage is a clear measurement of how efficient your system is. However, if we just talked about the SG of the final runnings, that would be dependent on what your OG is. If your expected OG is 1.090 and your final runnings are 1.010, that's going to be really high efficiency. However, if your expected OG is only 1.030, that same final running reading 1.010 isn't going to show such a high efficiency percentage.