Performed preventative maintenance for a Lennox furnace model #EL280UH110P48C-02, serial #5915L06395. I powered the system down and removed the access panels. Removed and cleaned carbon off of the flame sensor and cleaned out the burners and burner box. Replaced the air filter size 20x25x1. I checked the pressure switch for clogs and tested the drain line with several bottles of water to ensure that there are no leaks or clogs. Checked all electrical connections to ensure that they are secure and in good condition. I powered the system up and called for heat. Took a combustion analysis test and received the following readings, o2 is 14.1% and the co levels are 8ppm. The inducer motor amp draw is at .23 and the blower motor amp draw is 5.7. The supply temp is 122°F. The system is operating properly at this time. Homeowner receives a senior discount reflected in the price.