Performed AC maintenance on a Lennox system. Upon arrival customer had questions about his S30 thermostat. Questions were answered and a energy saving schedule was created for the homeowner. Units cooling temperature split is 20 degrees. Condensate lines are clear. Filter is very dirty and was replaced today. Indoor blower wheel is slightly dirty. Indoor amp draws are ok. Outdoor coils were heavily caked in dirt but chemically washed today. Compressor and fan amperages are in range. Refrigerant charge is ok. Recommending surge protection to protect the equipment. System was running at end of appointment