If one piece of equipment fails it may affect an entire system. DDC hasbetter reliability. Each controller can operate as a stand alone unit. If power to a piece of equipment is interrupted, it will notaffect the operation of other equipment in the system. Failure of DDC is very uncommon.
Service typically consist of boardreplacement, which is simple and takes little time.
Maintainability Pneumatic controls require regular recalibration due to drift. There are fewer components to maintain in DDC systems and thesystem does not need calibrating due to drifting. Flexibility DDC allows easier and more economical changes or additions. Changes or additions to pneumatic controls require new ordifferent controllers, re-piping and often wiring, and recalibration. Changes or additions to DDC require new control strategieswhich can be easily changed at the central unit.