What does tonnage refer to in the context of HVAC?

Tonnage in the context of HVAC refers specifically to the measure of heat transfer capacity of an air conditioning system, represented in BTUs (British Thermal Units) per hour. The term is derived from a historical context where it referred to the amount of ice needed to cool a space, where one ton of cooling is equivalent to the cooling capacity that would be required to melt one ton of ice in a 24-hour period.

This unit of measurement is essential in determining the size and efficiency of air conditioning and refrigeration systems, as it allows professionals to quantify how much heat an air conditioning system can remove from a space in a specific amount of time. Understanding tonnage helps in selecting the appropriate system size to ensure efficiency and comfort in heating and cooling applications.

The other options do not correctly define tonnage in this context. Time, weight, and pressure are relevant concepts in HVAC but do not pertain to the specific capacity measurement that tonnage represents regarding cooling performance.