Commercial Preventative Maintenance on rooftop units. Replaced filters and belts(if applicable) on York unit.âš ï¸ Perform precision tune up on all heating systems. Pulled and cleaned burners. Test return and supply temps, main flame safety sensors and ignition, gas pressure, combustion test, and amp draw on motors. Checked all electrical inside of the units. Inspected heat exchangers for any visual defects. All RTU’s are heating with no issues at this time.