when I wanted to go up to 10 gallon batches I tried Denny's batch sparge method because it was easier and cheaper to use a cooler with a braid and I didn't have to worry about a manifold or channeling.
False bottom design is an Achilles' heel when continuous sparging. The use of slotted manifolds or braids and non-cylindrical tuns are the major reasons why home brewers obtain subpar results from continuous sparging. Continuous sparging is only better than batch sparging if a brewer pays attention to physics. Continuous sparging is an exercise in applied fluid dynamics because it works by displacing the sugars in the mash with water. Batch sparging works by diluting the sugars in the mash with water. Equal dilution is much easier to obtain than equal displacement. Unequal displacement (a.k.a. channeling) is a recipe for subpar results when continuous sparging.
False bottom design was the last thing that I groked about continuous sparging. The percentage of open space and the shape of the holes is critical to maximizing the technique. The 3/32" on 5/32" domed stainless steel false bottoms that are available on the web have far too much open space to be good continuous sparging false bottoms, and the round holes can clog leading to channeling. Examining the false bottoms that are used in commercial tuns revealed that they have been 15 and 20 percent open space. They also have sloted holes, which help prevent clogging. I decided to take a chance when I noticed that Adventures in Homebrewing was offering a 16% open space false bottom. My average extraction rate shot from 30/31 PPG to 33/34 PPG with the occasional 35 PPG batch. I did not make single change in my process other than switching to a different false bottom.
To put things into context, Briess claims that their average DBFG percentage is 80.5% (http://www.brewingwithbriess.com/Assets/PDFs/Briess_PISB_2RowBrewersMalt.pdf
), which translates to 46 x 0.805 = 37 PPG. An extraction rate of 35 PPG translates to an extraction efficiency of 35 / 37 = 95%. Now, that is a non-weighted efficiency because there are usually other lower yielding malts in the tun.
With that said, I am not trying to convert anyone to continuous sparging. Brewers that are happy with their results should stick with what they are doing. There is nothing more frustrating than switching to another technique and achieving less than desired results. However, for those who may be curious about trying continuous sparging, mash design is a huge part of the equation. One cannot throw just anything together and expect good results. That's the major strength of batch sparging as I see it. Crush is also important. However, what constitutes a good crush when continuous sparging is different than what constitutes a good crush when batch sparging. Double milling or setting the rollers on a 2-roller mill much closer than 1mm usually results in lower extraction rates when continuous sparging because husk integrity is critical to the technique. A continuously sparged mash bed needs to be stratified with the largest particles on the bottom in order to promote equal flow through the bed.