It determines which fans, pumps, and chiller run and at what speed or capacity. It dictates the position of every damper and valve in a system. The DDC system is the "brain" of the HVAC system. This "subsystem" is vital to the performance and basic operation of the overall HVAC system. Groups of DDC controllers, networked or not, form a layer of systems themselves. Digital outputs are typically relay contacts used to start and stop equipment, and analog outputs are typically voltage or current signals to control the movement of the medium (air/water/steam) control devices such as valves, dampers, and motors. ![]() Digital inputs are typically (dry) contacts from a control device, and analog inputs are typically a voltage or current measurement from a variable (temperature, humidity, velocity, or pressure) sensing device. 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). The program features include time schedules, set points, controllers, logic, timers, trend logs, and alarms. start the blower).Ĭentral controllers and most terminal unit controllers are programmable, meaning the direct digital control program code may be customized for the intended use. Then the control system draws a conclusion what action has to be taken (e.g. Usually a sensing device is used to compare the actual state (e.g. ![]() HVAC (Heating, Ventilation and Air Conditioning) equipment needs a control system to regulate the operation of a heating and/or air conditioning system. Control system for heating, ventilation, and air conditioning equipment
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