200-ton rotary chiller, there are a few ways to estimate load on the machine:
Heat balance, evaporator side
Heat balance, condenser side
% of full load amps
Doing heat balance on both sides, usually yields two fairly different values. This is probably due to instrumentation limitations which result in imprecise measurement of fluid flow rates. Usually flow through the evap or condenser is estimated based on dp.
Usually the heat balance load values don't agree too well with % of full load amps, either. Not sure which is the most indicative of actual operating tonnage of the machine.