My deer Run RO recirculates but it is done by simply opening a recirculate needle valve just before the concentrate flow control valve, and that sends a portion back thru the high pressure pump and membranes again. I've used mine for 6 seasons now. Originally mine had a Honda gas engine, but after I got grid power to the sugarhouse, I converted it to electric. Mine will take 2% sap to 8% in one pass, but this year I had no 2% sap. By opening the recirculate valve I can get 1.2% sap to 6% in one pass, then I draw from my head tank and recirculate thru again and I got it to 10-12%. Saves lots of time and wood. On my 3x8 boiling at 70-75 gph, the Deer Run RO can be run to match the boil rate but I prefer to run the concentrate flow faster and then recirculate again for even higher concentration. I've run as high as 14% without issue, but once I was doing other things while recirculating the RO, it got to 18% and plugged the membrane enough that I had to run a 4-5 minute permeate rinse to clear the membrane then I could resume running the RO, this time adding more fresh sap to the head tank while I was boiling. The Deer Run does good up to 14%, does not like 18%, I'm not sure about between those two, I never tried. Ray at Deer Run says he generally goes to 15% max.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.