Today I came to Shaohua’s Aspen home because the boiler stopped working a few days ago. Shaohua has since shut the gas and electrical off to the unit but has shown me the error code displayed at the time of failure. The error code indicates a tripped or failed temperature sensor. Upon inspection of the 15 year old system I tuned the power and gas on to the unit and it fired up. I did find the zone controller has failed and does not turn the system on when the garage zone is asking for heat. The last maintenance was done on this system 3-4 years ago. This system has a horizontal heat exchanger that must be cleaned every 1-2 years.