I must cast my vote for paralleling these together as Dave suggested.......with the separator, reservoir and float setup. In addition, when you're looking at an oil & gas equalization deal with multiple pumps you have to strongly consider the flex and harmonic vibrations inherent in this kind of arrangement.
Hussmann had four compressors' crankcases tied together with an 1 1/8" or 1 3/8" equalizer on their "New System" of the early seventies. D/B was doing the same thing with the "Paraflex" in the late sixties. It wasn't uncommon to walk into a very quiet compressor room to find the equalizer line, discharge manifold or suction manifold had sheared off and laying on the floor in a pool of oil.
That's when they learned how copper will crystallize under vibrational stress and how to beef up the frame structures to eliminate the flex. Of course, then AC&R came along and solved the problem with the float controlled system.
Thanks for all of the great input. I am just another dingleberry engineer, but I try to get field input so I don't build something techs cuss at too much. I've designed quite a few chillers, but they are all high temp/AC type systems.
Most of my stuff is multiple circuit, but all of the circuits are totally independent. I am going with the tandem/parallel setup because of some serious rebate potential from the power company that the brewery owner would like to get in on. I also always use scrolls. Even the med. temp stuff is scroll (copeland ZB models). I've had no problems with the 2 dozen or so of those that I have built.
Sounds like I should just do the whole level control system and not mess around.