TSUK,
I'd go for a Data Logger on the Incoming Mains.
I've used these before to good effect logging Voltage, Current, PF and Max Demand.
They give a real-time "look" at what is happening in a circuit.
Your output is on a laptop.
Is this place spread over 3 Phases, with a Neutral?.
Refrigeration is a constant current once the compressor is started, only thing that would upset that would be if the thermostat was set too low or the contacts were welded shut.
The compressor would go out on high pressure after a time though
