Arrived onsite for maintenance for one gas fired high efficiency boiler. Requested the customer turn on the thermostats up to heat and confirm operation of the boiler and each zone. Turned the boiler off and removed heat exchanger cover. Cleaned heat exchanger. Performed a visual inspection of all electrical and inspected all external water components such as the exp tank, fill valve, backflow preventer and the circulator pump. Clear condensate lines. Confirmed system is operating and heating properly at this time.