HAS AN OLD UNIT AND A NEW UNIT. CLEAN AND CHECK TO MAKE SURE SYSTEM WAS RUNNING PROPERLY. CHECK AIR FILTER, THERMOSTAT, CHECK AIRFLOW, ENERGY CONSUMPTION, FAN CONTROL, HUMIDIFIER, HEAT EXCHANGER, HIGH LIMIT CONTROL, AND ALL ELECTRICAL CONNECTIONS. CLEAN AND CHECK BURNERS AND BURNER OPERATION. LUBRICATE ALL NECESSARY MOVING PARTS, AND ADJUST BLOWER COMPONENTS.