A one-tonne refrigerating machine means that when One tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min.
In order to express the cooling capacity of a refrigerating machine, i.e., the rate of heat removal from the refrigerated space, the common and standard unit generally used is a ton of refrigeration.
In FPS units, one ton of refrigeration is defined as the capacity to freeze one ton of water from 0°C (32 F) in 24 hours. It is the withdrawal of heat at a rate of 200 BTU/min. This equates to 12,000 Btu/hr or 12,000 Btuh or 12658 kj/h or 210 kJ/min.