Hi Quinton
the oil is cooled by a glycol solution for frost protection. Glycol/water mix is circulated thru a second coil in the evaporative condenser. Oil coolers are more commonly shell and tube, but always cleanable. Rubbered, semi welded plates are often used on chiller for evaporator, the semi refers to the fact that they wouln't have any rubbers on the refrigerant side, only the process side.
Dave
those contactors sure do keep you on your toes, even though the voltage would dictate smaller contactors for the load they are always generously sized.
Regards. Andy