Performed preventative maintenance for gas furnace. Merv 11 Filter was replaced in the spring and won’t be due till spring 2023. Cleaned the burners, flame sensor and burner box. Made sure inducer port is clear. Inspected all the electrical components. Confirmed proper high and low voltages. Tested the operation of the fan, stage 1 heat and stage 2 heat from the communicating thermostat. Inspected the gas piping going into the furnace. Performs a combustion analysis on the furnace. System is operating at 84% efficiency with a CO level of 20ppm. Tested the amp draw of the blower and inducer. Both were operating within the manufacturer spec. System is operating properly at this time. Model #SL280UH090V36B-04 Serial #5916K02434