Performed preventative maintenance on Lennox AC system. Replaced 16x25x1 air filter. Tested evaporator coil pan and condensate line for proper drainage. Temperature split was 0° and a low refrigerant charge was discovered. Quoted customer for 3 pounds of refrigerant and easy seal and die and performed the work. Charged 3 lbs. of R410-A and applied the easy seal and die to the unit. This system was rated for a subcool of 7. After charging 3 lbs of refrigerant the subcool was at 7 and the system was accurately charged. There is now a supply air temperature of 52° with a temperature split of 18°. Compressor- 5.6 RLA Condenser fan motor- 0.6 FLA. Both of these readings are within the amperage rating for this unit.