Arrived on site to perform an annual tune up on a Viessmann boiler. We provided an estimate for the work which was accepted. We started by turning the gas and power supply off to the boiler. We then disconnected the gas line and removed the front plate to the heat exchanger. We inspected and cleaned the igniter electrodes, flame sensor, and the heat exchanger. We sprayed the heat exchanger with citrusurf and then rinsed with water. Once clean, we put the boiler back together and test ran it to perform a combustion analysis and to check for CO leaks. No leaks present. Next year we may want to think about replacing the rear refractory as it is starting to crack near the edges. Thank you for your business!