I have a chiller, and two hydro units with a res and 4 grow pots all from 5 gallon buckets. The single chiller capacity far exceeds the needs of both sets combined, but obviously it has one loop through it. I figure if I add a heat exchanger of some sort in the first hydro unit and pass the cooled water through that on the way to the second unit and back to the chiller it should be ok, Is there a safe material to use for a heat exchanger (not copper of course), is such a thing available off the shelf, or is there a better way already in common use?
So, I am happy to report it all works! I ordered some 3/8 thin wall stainless which is a fucker to bend, I like the water or baking soda methods, but once bent it was a perfect chiller coil. I pump from a pump in unit one reservoir through the chiller, then through the chiller coil in unit two reservoir, and from that it returns to the unit one reservoir. Both reservoirs and their associated grow stations are separated paths so different feeding schedules are fine. Temps througout the system remain at whatever I set the chiller at since it is based on return path temp for the chiller, a sample anywhere in the system is plus/minus 1 deg. I also insulate my pots.