A 3-ton air conditioning unit can hold 6 to 12 pounds of Freon, depending on the unit. The exact amount of Freon needed is determined by a variety of factors, such as the type of unit and where it is installed.
The amount of Freon or other refrigerant necessary to fill any size air conditioning unit depends on factors such as the size of the evaporator coil and whether the air conditioner is an all-in-one, self-contained exterior unit or a split system unit in which the condenser and compressor are outside and the air handler and coil are inside. The length of the lineset, the copper pipes which connect the outside condensing unit to the indoor evaporator coil on a split system unit, also affects the amount of Freon necessary to fill the unit, as does the diameter of the lineset tubing.
The seasonal energy efficiency ratio of the unit also impacts the amount of Freon an air conditioner requires; the higher the SEER rating, the larger the evaporating coil. The larger coil surface makes the air conditioner more efficient while increasing the amount of Freon needed to fill the unit. Freon, also known as R-22, is regulated by the Environmental Protection Agency, and only an EPA-certified technician can buy and handle it.