Brewhouse Efficiency Troubleshoot

[Lakeside_Brewer]

BLUF: Brewed an AG batch today with a new kettle. Hit pre-boil gravity, but shorted post-boil gravity by 10 points. I normally have ~.5 gal of trub after transferring to the fermenter; I hit my batch goal. However, I ended up with ~30% more trub. I let the trub sit in a pitcher and after 3 hours there was a good .5 gallons of wort sitting on top of the trub. I believe a proper boil off wasn't achieved and that would account for the excess wort with the trub and not hitting post-boil gravity. Does that make sense to anyone else?
Cheers

 

[urg8rb8]

What was your wort volume in the fermenter before pitching the yeast?

 

[doug293cz]

Can't help you without the numbers. To fully diagnose efficiency issues, the following measurements are needed:

• Grain bill weight
• Strike water volume (everything prior to initial run off)
• SG of wort at end of mash, or first runnings SG
• Sparge process (fly, batch, none)
• Sparge water volume (for each batch sparge if more than one)
• Pre-boil volume
• Pre-boil SG
• Weight & type of any sugar added to the boil
• Post-boil volume
• Post-boil SG (OG)
• Volume into fermenter

Accurate measurements are critical, since the efficiency calculations cannot be better than the measurement accuracy. All volumes should be corrected for thermal expansion to 68˚F, or the volume measurement temperature reported, so that corrections can be made. Hydrometer measurements should be taken with the wort temp within 20˚F of the hydrometer's calibration temperature, and then corrected for the temperature at which the measurement was made.

Mash Efficiency = Conversion Efficiency * Lauter Efficiency
Brewhouse Efficiency = Mash Efficiency * Fermenter Volume / Post-boil Volume

With the measurements listed above, all of the factors in the above equations can be calculated. Conversion efficiency should be greater than 95%. Lauter efficiency is a function of sparge process and grain weight to pre-boil volume ratio, and maximum achievable can be predicted (but not as accurately for fly sparge.) Once you know which efficiency factor is lower than what should be achievable, then you know what part of your process needs to be addressed.

Brew on

 

[Lakeside_Brewer]

Gents,
Thanks for the quick responses:

Grain bill weight: 11lb
Strike water volume (everything prior to initial run off): 3.69 gal; plus ~.34 gal to get up to infusion temp
SG of wort at end of mash, or first runnings SG: 1.058
Sparge process (fly, batch, none): Batch
Sparge water volume (for each batch sparge if more than one); .4 gal and 3 gal
Pre-boil volume: ~3.25
Pre-boil SG: 1.058
Weight & type of any sugar added to the boil: 4 oz brown sugar
Post-boil volume: Failed to take this measurement
Post-boil SG (OG): 1.081
Volume into fermenter: 3 gal

I believe what also contributed to this was that I was flipping between Beer Smith and Brewer's Friend Beta and numbers were not complimenting each other.
Cheers,
Jas

 

[pricelessbrewing]

Last time I looked, brewers friend is reporting higher than it should be.

Assuming 3.25 gallons is accurate, you should be able to find the new volume by the two sg and the sugar addition. Either way, it doesn't matter much as you can get the mash and brewhouse efficiency from the preboil numbers just as well as the post boil numbers.

 

[doug293cz]

Gents,
Thanks for the quick responses:

Grain bill weight: 11lb
Strike water volume (everything prior to initial run off): 3.69 gal; plus ~.34 gal to get up to infusion temp
SG of wort at end of mash, or first runnings SG: 1.058
Sparge process (fly, batch, none): Batch
Sparge water volume (for each batch sparge if more than one); .4 gal and 3 gal
Pre-boil volume: ~3.25
Pre-boil SG: 1.058
Weight & type of any sugar added to the boil: 4 oz brown sugar
Post-boil volume: Failed to take this measurement
Post-boil SG (OG): 1.081
Volume into fermenter: 3 gal

I believe what also contributed to this was that I was flipping between Beer Smith and Brewer's Friend Beta and numbers were not complimenting each other.
Cheers,
Jas

Your numbers don't add up. Let me explain:

Your mash contained 11 lb of grain, and 4.03 gal (3.69 + 0.34) of water. This is a water to grain ratio of 4* 4.03 / 11 = 16.12 / 11 = 1.465 qt/lb. A mash of this thickness should have an SG of 1.083 - 1.084 @ 100% conversion efficiency (ref: http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency#Measuring_conversion_efficiency.) A mash SG of 1.058 would put your conversion efficiency at about 100% * 58 / 83.5 = 69.5% (a more rigorous calculation puts conversion eff at 66.9%), which would be pretty bad. Conversion efficiency in excess of 95% is readily achievable by homebrewers.

When you drained the MLT, the grain should have absorbed about 0.12 gal / lb of grain, or 1.32 gal, giving you a first runnings volume of 4.03 - 1.32 = 2.71 gal. You may have some undrainable MLT volume which would reduce the first runnings volume even further.

You sparged with a total of 3.4 gal, and since the grain is already saturated, and the undrainable volume full, you should have recovered a total of 3.4 gal of sparged wort from your second and third runnings. Your pre-boil volume should have been 2.71 + 3.4 = 6.11 gal, less the undrainable MLT volume. You state your pre-boil volume as 3.25 gal. Where did the rest of the wort go?

You also state your pre-boil SG as 1.058, which is the same as your initial wort SG. This is not possible if you added sparged wort (which is necessarily lower SG than the mash/first runnings SG due to dilution) to your first runnings.

I'll skip doing any further analysis since the measurements look like nonsense. To be able make accurate efficiency calculations, all the measurements need to be accurate. Otherwise it's just GIGO.

Brew on

 

[Lakeside_Brewer]

Doug,
My apologies. Pre-boil volume should have read 5.25 gal. Also, the first runnings never even reached the 2 gal mark; it looks like I need to check my mash tun dead space again. I didn't take a first runnings gravity reading; I apologize for misunderstanding. I'm still a novice AG brewer so I appreciate your insight. Like you stated: GIGO. I may not have measured the strike water properly. No need for further analysis. I'll chalk this up to brewer error, remeasure the deadspace on my mash tun, and have a print out of the measurements you asked for when brew in the future.
Cheers,
Jas

 

[madscientist451]

I plugged your numbers in with 11 lbs of grain and a pre boil volume of 5.25 and if you figure 4 gallons post boil, your gravity of 1.080 is about 75% efficiency, which is pretty good. Many brewers don't worry about trub, they just dump everything into the fermenter.
It looks like you used about 7.5 gallons of water and your volume came up short. The easiest thing to try is to rebrew the same beer but use 8.5 gallons of water and see what you get.
Once you get your volume/gravity issues sorted out, move on to a different recipe. I think you'll find that once you figure out your water volume for your system, you can tweak it without too much fussing and get predictable results.
I was always coming up short on my volume, even after meticulous measurement of my water. Lately, I just get 8-8.5 gallons of water ready (for 5 gallon batch) and just go ahead and brew and I always get enough volume. Your brew kettle and heat source and boil intensity will make a difference in your post boil volume and gravity, so just experiment with your water volumes and see what works for you.
If you are really interested in crunching your efficiency numbers, pull samples of the wort at first runnings, and at the end. If your final runnings are above 1.020, you are leaving usable fermentables in the mash tun. Going much below 1.020 isn't recommended.
I used to be fussy about all of that but have decided to take a more laid back approach and just use 8-8.5 gallon of water, and not worry about it.
I've done the quick batch sparge method, but have found if I take some extra time, add boiling water at end of mash to bring up the temperature, recirculate (just drain into a pitcher and pour back in the top) and sparge and run off fairly slow I get good efficiency numbers.
My method may not work for you, everyone has their own way, find what works best for you and the equipment you have. There are many ways to make a fermentable wort, you don't have to conform to any particular method, you can even blend different methods as it suits you.

 

[rippajak]

I believe a proper boil off wasn't achieved and that would account for the excess wort with the trub and not hitting post-boil gravity. Does that make sense to anyone else?
Cheers

I believe you're on track with this.

If your pre-boil gravity was on-mark, but your post-boil gravity was low, my first thought would be that you boiled off less liquid than you anticipated.

If it is a new boil kettle for you, I would suggest taking accurate pre-boil and post-boil volume measurements on your next few brews. Boil-off can vary based on kettle surface area (among other factors), so switching to a new kettle may have resulted in a lower boil-off rate. This would be especially true if your new kettle is narrower than the one you used previously.

I can't speak for how long it's been since your last brew, or what the weather is like where you live, but for me the ambient humidity has climbed drastically in the last month or so. That can also have an effect on your boil-off rates, with drier air tending to soak up more liquid.

 

[brewkinger]

Boil off seemed to be a problem recently with the high temps and humidity that we had here on the east coast.
Myself and 3 other guys that I know brewed this past weekend and each of us experienced less than normal evaporation.