The term "3-ton evaporator" refers to the cooling capacity of an air conditioning system, specifically the evaporator coil. In this context, a "ton" is a unit of measurement for cooling capacity, not weight. One ton of cooling capacity is equivalent to removing 12,000 British Thermal Units (BTUs) of heat per hour.
Therefore, a 3-ton evaporator has a cooling capacity of 36,000 BTUs per hour (3 tons x 12,000 BTUs/ton). This means that the evaporator can remove 36,000 BTUs of heat from the air in one hour of operation. It's important to note that the cooling capacity of an air conditioning system is only one factor to consider when determining the appropriate size for a specific space, as factors such as insulation, room size, and climate also come into play.