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-   -   False bottom and recirculation = efficiency problems? (http://www.homebrewtalk.com/f36/false-bottom-recirculation-efficiency-problems-372212/)

A_C 12-05-2012 10:57 PM

False bottom and recirculation = efficiency problems?
 
I just moved and upgraded my system :), but now I am having efficiency issues :confused:. I'm using 3 keggles on a single tier with two pumps. I do constant HERMS-style recirculation and I fly sparge.

My false bottom in the MLT is high (there's 2.5 gallons of liquid under FB). To compensate, I add an extra 2.5 gallons to the mash (to get the desired thickness). But, to not overshoot my pre-boil level, I have to reduce the amount of sparge water accordingly. I am trying to figure out if this is causing issues. (Note: though my false bottom is high, I don't have a lot of dead space)

Concerns:
- liquid under false bottom isn't touching grains (but I do constant recirculation so shouldn't that make use of the liquid?)
- less sparge water may result in less lauter efficiency
- mainly, I'm worried that the false bottom and the constant recirculation are messing up my mash/efficiency somehow (my new toys are making my brewing more complicated :()

Do you see any problems here? If not, I may need to look elsewhere in the process. Thanks and I really appreciate any help

Bobby_M 12-05-2012 11:22 PM

Yes, a more dilute mash will often lower efficiency. Why would you install a false bottom so high? To keep it above the bulkhead drain I'd imagine, but you'd typically run a diptube through the center to fix that problem.

What is your desired mash thickness that you add 2.5 gallons to?

A_C 12-06-2012 01:10 AM

Ya, my false bottom is above the bulkhead. I guess I could rig the false bottom to fit under the bulkhead then use a dip tube.

I have tried mashing at 1.25 qt/lb and 1.5 qt/lb (above the false bottom). As long as I don't mash with more water than I am targeting for pre-boil volume, I shouldn't be diluting my pre-boil gravity, right?

wolfman_48442 12-06-2012 01:36 AM

I've got a darn high false bottom in my mash tun, recirculate mash through my herms and fly sparge. I average 85% efficiency.
Depending on style, I'll use anywhere from 1.24 qt/lb - 2 qt/lb mash ratios. Doesn't effect my efficiency.
Are you getting channeling in your grain bed? You don't have to recirculate at max velocity, just a steady trickle while maintaining 1" or so of water over the grain bed is fine.

Bobby_M 12-06-2012 07:35 PM

The more dilute your mash is, the less sparge you can process through it. That applies whether you fly or batch sparge.

You mentioned that you'd need to rig up a diptube if you moved the FB lower. You don't have one underneath the FB now? How is it that you have hardly any dead space without a diptube?

A_C 12-06-2012 09:58 PM

I do have a diptube under the false bottom. If I lowered the FB, I would have to rig it so the diptube could run through through the FB.

Thanks for the help

MaltyHops 12-07-2012 07:27 AM

Quote:

Originally Posted by A_C (Post 4656986)
I do have a diptube under the false bottom. If I lowered the FB, I would have to rig it so the diptube could run through through the FB.

Thanks for the help

What about using something to fill up the dead space under the false bottom?

Maybe using a combination of steel nipples, couplings and plugs to make what is essentially a closed tube that is filled with water?

I've actually got a problem with my version of jkarp's Countertop Brutus 20 where it might be good to have something to take up space in the kettle - maybe something like the closed tube setup like the above, but using larger pipe sizes like 2 inch fittings.

Question is ... will an enclosed water-filled arrangement be safe if heated to boiling point or the pressure build up make it a potential bomb?

I would actually use it at mashing/mashout temperatures only.

ILoveBeer2 12-07-2012 10:47 AM

I would not build a closed tube to fill dead space under the false bottom. Unless you own the pipe and fittings, you are going to spend more than buying/building a diptube.

BudzAndSudz 12-07-2012 12:18 PM

I have a similar issue on my brand new recirculation system. What I found was that you really need to let the grain bed settle for 10-15 minutes after dough-in before you kick on your pump. That way the grains settle homogeneously and you get even flow through the grain bed. If you kick on the pump immediately, that heavy flow of liquid pushes the grains out of the way and forces channeling to happen.

mcl 12-07-2012 07:41 PM

I have the same problem to a certain extent. I believe it all comes down to having less sparge water available to rinse the grains. Sometime I will get around to modifying the FB base so it sits lower.


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