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Old 01-28-2013, 06:17 PM   #1
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Default Dealing with large amounts of deadspace

Bottom-Line, Up-Front: I have a LARGE amount of deadspace under my mashtun FB and I'm getting TERRIBLE efficiency; I'm looking for things that I can do to maximize efficiency. 98% of my efficiency issues are NOT crush-related so the typical knee-jerk crush answers are not appropriate here.

While I finish building my custom false bottom, I'm using a false bottom that came with my kettle (fits the mashtun perfectly); my current false bottom is built like a tank but has a HUGE amount of dead-space below the grain bed.

Yesterday was my first brew day on my new system and my efficiency was TERRIBLE and I'm looking for advice on how to maximize efficiency with my current false bottom.

I'm used to mashing with a stainless mesh tube attached to a ball valve and then double batch sparging -I got GREAT efficiencies (75%-85% depending upon the exact recipe and process) on my old system but ABYSMAL efficiency yesterday (around 60%...).

On my old system I used a pretty loose mash (3 liters / kg) so I tried the same on my new mashtun and there's so much deadspace under my new FB that the top 2 inches of the mash had NO liquid on them so I had to make the mash even more liquid -I recirculated throughout the entire 60 minute mash hoping that that would help. (My mash tun is double wall insulated stainless so it holds temps fantastically throughout a 60 minute mash while recirculating.)
-This meant that I then had less liquid available for sparging so I also had a LOT of sugar left.

I was also making a 5 gallon batch in a mashtun with a 13 gallon capacity so my grain bed wasn't very thick and the liquid ran through it very quickly -i also recirculated the sparge addition but I'm just using a hose and because of the significant amount of dead-space the liquid is NOT being even remotely evenly distributed on the surface of the grain bed.


I have a "perfect storm" for bad efficiency and I realize that, but I'm curious if there's anything that I can do with the system as it is currently to try and increase my efficiency.

(I'm going to brew a bigger batch next time and I'm going to try and get my custom false bottom finished as soon as possible but what else can I do?) -I'm not willing to implement a rotating sparge arm, but if anyone has some novel solutions for more evenly spraying my sparge additions, I'm all ears.

When you have a large amount of dead-space under your false bottom do you HAVE TO go with a looser mash or does constantly recirculating the mash mean that this just isn't an issue?

(I have a 5500w electric kettle so I can gather more wort than I need to get more sugar out and then run it full-blast for an hour to boil off more liquid, too; I think this will get me a few more points because my final runnings yesterday were 1.010 so I was leaving a LOT of sugar behind.)


Adam
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Old 01-28-2013, 08:00 PM   #2
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If your dead space is lets say....a gallon. Why not convert your recipes to 6 gallons and leave a gallon in the tun. Your efficiency would then represent a more realistic number. The cost per reicpe should be cheaper than replacing your setup. Just my 2 cents.

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Old 01-28-2013, 08:09 PM   #3
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I think you need a bigger grain bed. If your dead space is too big you'll have too much "free" water and as you draw it out, even while recirculating, the water will sort of tunnel down through the grain too quickly leaving a lot of sugar behind in dead areas. Use the bigger grain bed and recirculate very slowly so the water filters through the grain gently and evenly and you will extract as much sugar as possible. If that's not it, then constant recirculation could be a problem. Get the temperature you want and let the grain rest in motionless water as long as possible. Then sparge at a very high temperature (180-200) very slowly to dissolve all possible sugars and get a better efficiency

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Old 01-28-2013, 08:17 PM   #4
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Extend the pickup tube closer to the bottom of your MLT. The closer it comes to the bottom of the kettle the more liquid it will pickup before siphon breaks. You'll need to experiment with distance as the grainbed will push down on the falsebottom a bit and if you extend too close to the bottom then when the weight of the grainbed pushes on the false bottom it may seal off your pickup tube. A simple test would be to use a piece of tubing that can be jammed into place. It sounds like you'll have this problem whether it's 100% water or an actual mash, therefore it should be easy to test with water.

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Old 01-28-2013, 08:17 PM   #5
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why not fill that deadspace with something inert, like glass marbles? they'll fill up that space and the liquid will flow around and between them. you would need to take them into consideration in your process, as they will absorb heat. it will make your MT heavier.

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Old 01-28-2013, 11:11 PM   #6
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Quote:
Originally Posted by moffatt163 View Post
I think you need a bigger grain bed. If your dead space is too big you'll have too much "free" water and as you draw it out, even while recirculating, the water will sort of tunnel down through the grain too quickly leaving a lot of sugar behind in dead areas. Use the bigger grain bed and recirculate very slowly so the water filters through the grain gently and evenly and you will extract as much sugar as possible. If that's not it, then constant recirculation could be a problem. Get the temperature you want and let the grain rest in motionless water as long as possible. Then sparge at a very high temperature (180-200) very slowly to dissolve all possible sugars and get a better efficiency
I agree with all of this except for the 180-200 F water; tannins == bad.


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Old 01-28-2013, 11:12 PM   #7
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Quote:
Originally Posted by stpug View Post
Extend the pickup tube closer to the bottom of your MLT. The closer it comes to the bottom of the kettle the more liquid it will pickup before siphon breaks. You'll need to experiment with distance as the grainbed will push down on the falsebottom a bit and if you extend too close to the bottom then when the weight of the grainbed pushes on the false bottom it may seal off your pickup tube. A simple test would be to use a piece of tubing that can be jammed into place. It sounds like you'll have this problem whether it's 100% water or an actual mash, therefore it should be easy to test with water.
I don't have a pickup tube or a siphon, I have a center bottom drain in my mash tun so I drain all liquid except for maybe 100ml. (Had a 1 1/2" tri clamp welded into the center of my mashtun has a bottom drain.)
My efficiency problems aren't related to leaving liquid in the bottom of the mash tun; they're related to the huge amount of deadspace.
(I REALLY need to get my new false bottom finished....)


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Old 01-28-2013, 11:15 PM   #8
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why not fill that deadspace with something inert, like glass marbles? they'll fill up that space and the liquid will flow around and between them. you would need to take them into consideration in your process, as they will absorb heat. it will make your MT heavier.
That is some of the most creative thinking I've heard in a long, long time; that's actually quite genius!

-I have a bottom drain mashtun and I'm afraid the marbles might clog the drain / ball valve. I'm also not sure how I'd ever get the false bottom to set in place with the marbles there. (There are 4 huge 1" pieces of stainless bent into a rectangle which holds the mashtun about 2" off of the bottom of the MT.

That is a seriously creative solution, though!

If I had a side ball valve+ dip tube combo in a keg that sat along the outside ring that would be a really fantastic solution!


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Old 01-29-2013, 06:49 PM   #9
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I had a similar issue. The "legs" that hold the False bottom up, I cut them down as short as I could to eliminate the space under the False bottom. On my set up I had to make a dip tube setup because it moved the False bottom below my side valve.

In short the best solution is to eliminate the dead space.

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Old 01-29-2013, 08:11 PM   #10
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Originally Posted by samperry007 View Post
I had a similar issue. The "legs" that hold the False bottom up, I cut them down as short as I could to eliminate the space under the False bottom. On my set up I had to make a dip tube setup because it moved the False bottom below my side valve.

In short the best solution is to eliminate the dead space.

I've thought about doing that myself. Honestly, not a bad solution at all.


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