Slip dual vessel mashing

[akithegood]

I've been using a 2 vessel RIMS system for a while now. The MLT is a 30-liter kettle with false bottom and a PID-controlled 3 kW heating element and the BK is a 50-liter kettle also using a 3 kW element. It's great for 19 l batches of any strength, but double (38 l) batches are limited to about 1.050 OG because the MLT can't hold much more than 8 kg's of malt with a reasonable water-to-grain ratio.

What I'm thinking of is using my BK as an extension for the MLT. I would mash in with, for example, 12 kg's of malt and 18 litres of water. I would also heat an additional 18 litres of water to mash temperature in the BK, then recirculate the wort from MLT to BK and back to MLT. Combining the mash-in water and the additional water in the BK, my water-to-grain ratio would be 3 liters/kg, equal to a mash that would need closer to 50-liter mash tun.

I've read of some people doing this, but nothing on how it affects the efficiency or other aspects of the beer. What do you think?

 

[acidrain]

Don't see why it wouldn't work. I'm unfamiliar with metric quantities. Would that be a full volume mash?
Would you have enough room to mash and reserve an amount for sparge?
Like any alteration to your system, you'll need to run a couple of batches to see how it affects your equipment profile.

 

[akithegood]

The numbers translate to roughly 26.5 lbs of malt and 19+19 quarts of water, so the total water-to-grain ratio is about 1.44 qt/lbs.

For a double batch of 38 liters (~10 gallons) I need about 45 liter (~11.9 gallon) boil volume, so I would be sparging with about 19 liters (~5 gallons).