[berniebenz]

Thanks Hack, for the well stated reply.
I understand that 1 Ton of heat transfer equals 12,000 BTU/hr.

My Q is more specific regarding this rating as a measure of HX performance, i.e. the specific “standard conditions“ if any, of this rating.
1. Heat source side Delta T, Flow rate, Fluid thermal and change of state parameters.
2. Sink side, same conditions.
3. Delta T across the exchange surfaces, ect.