how does it work?
With the DDC System or the "brain" of an HVAC system. Groups of DDC Controllers, networked or not, form a layer of systems themselves. This "subsystem" is vital to the performance and basic operation of the overall HVAC system. This process dictates the position of every damper and valve in the system. It determines which fans, pumps and chillers run and at what speed or capacity, therefore, allowing multiple users to run their preferred temperature.
The program features include time schedules, set-points, controllers, logic, timers, trend logs, and alarms. The unit controllers typically have analog and digital inputs that allow measurement of the variable (temperature, humidity, or pressure) and analog and digital outputs for control of the transport medium (hot/cold water and/or steam). Digital units are typically (dry) contacts from a control device, and analog inputs are typically a voltage or current measurement from the variable (temperature, humidity, velocity, or pressure) sensing device. Digital outputs are typically relay contacts, used to start and stop equipment, and analog outputs are typically voltage or current signals.