Fixing low efficiency due to dead space

[codekitchen]

Here's a pic of my new BIAB setup, using a 62 quart pot. The strainer basket makes it much easier to deal with the giant heavy bag of grains. I even installed a little pulley up above, so I can easily lift them out by the handle.

For lower gravity batches I nail the efficiency, I've gotten as high as 81% on a 1.047 5.5 gallon batch. But for higher gravities, I've discovered a big issue: there's about 3 gallons of liquid underneath the basket that essentially has no contact with the grains. I can't add more water without way overshooting my 5.5 gallon batch size, requiring hours of extra boil to get back down to volume. This would also be a deal breaker if I wanted to make a smaller batch, like a 3 gallon barley wine.

Of course the obvious solution is to just skip the strainer basket. But I'm wondering if anybody else has run into this, and if they have a clever way to decrease the volume below the basket. One option I've considered is capping a bunch of water-filled beer bottles, and laying them in the bottom to decrease the volume under the basket.

I could also get myself a pump and recirculate the wort, which would help with high-gravity 5 gallon batches but wouldn't really solve the 3 gallon batch problem.

Thoughts/suggestions?

 

[newnick]

Are you using a 5.5 gal. recipe or a 5 gal. recipe to start with?
I use a 44qt. pot like yours with the basket and I don't really think the dead space has any affect on how it turns out. I too put 5.5 gals. in the fermenter and sometimes have a lower gravity than I should.

 

[codekitchen]

5.5 gallons. I'm pretty confident it's the dead space. Like I said, I can hit my OG exactly on smaller OG batches < 1.050 or so. But I did my first high gravity batch with this setup, target 1.080 and mashed with 8.4 gallons, and only hit 1.057 actual OG in the fermenter.

I'm able to predict this exactly using Steven Deed's chart of Maximum Extracted Fermentables in a no-sparge mash, and plugging in the 15.5 pounds of grains and 5.4 gallons (8.4 - the 3 gal dead space). According to his experiments the maximum you can extract in that situation is 283 gravity points, which / 5.5 gallons is pretty much exactly the 1.057 that I hit.

 

[Bobby_M]

Hi
This isn't really dead space. Dead space is liquid volume that will not drain out of a vessel. The liquid below your basket IS participating in the mash. You can test this by taking a wort sample from the spigot and another one from the top of the mash and comparing the gravity. This is where a refractometer is handy.

Now maybe you DO have dead space also...which would affect efficiency. However, I would be looking at the crush and testing for 100% conversion.

 

[codekitchen]

I don't think I'm explaining myself very well, maybe the term dead space is the wrong one to use. I'm sure the liquid is pretty much uniform, so in that sense it's participating in the mash. However, the mash is much thicker than it otherwise would be, because of those 3 gallons that aren't mixed in with the grains.

Combine that with no sparging or recirculation, and I'm sure I left a ton of high gravity wort locked up in those grains when I tossed them. I think the next time I brew a beer this big using this setup, I'm going to try and "sparge" with hot water after I pull the basket out.

 

[newnick]

I've recirculated and sparged (tepid) and still come up a little short on big beers too, not quite as big as yours though.

 

[Bobby_M]

Yes, without any kind of recirculation, I agree that the mash ends up too dry. Here's a pretty easy fix idea for you. Cut the top 1/4" off your basket so that there is no longer a lip to get caught on the pot's rolled indent. Now the basket can sit on the bottom of the pot. If that's too close, just drop a couple stainless nuts into the pot as spacers.

 

[moclamd]

I'd recommend picking up a cheap Chinese pump off ebay for $20 and recirculating the Mash. Look for a post on here with a title along the lines of "Cheap compact pump". That thread has a ton of info about them.

 

[newnick]

Just out of curiosity what temp are you mashing at? I was thinking about going up a couple of degrees since the recirculating didn't help.

 

[wilserbrewer]

This is one of the reasons I am not a fan of strainer baskets. I have one and have never used it for brewing. I feel that if the bag is well fitted to the kettle, the strainer basket is not needed. Some people love using baskets, I have never seen the need.

 

[1MadScientist]

+1 on ditching the basket. You can easily lift the bag with a rope and a knot with your pulley.


This is a hangman's noose knot.

2/16/2013 by Mad Scientist Brewhaus, on Flickr