Direct Digital Controls (DDC) Building Automation Basics

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Key Questions

The following key questions are answered in this module:

What is a Building Automation System (BAS)?
A Building Automation System (BAS) is the technology that allows facility managers, maintenance technicians, and technical operators to control, monitor and adjust building-related equipment.

What is the purpose of a Direct Digital Control (DDC) unit?
The DDC provides the operator the capability of configuring and/or controlling the unit locally, rather than remotely.

What is the purpose of a Supervisory Control and Data Acquisition (SCADA) system?
The SCADA system provides the operator with the capability to control equipment remotely from a central room where other equipment is also being controlled, and data can be queried and processed for maintenance and troubleshooting purposes.

How is Time of Day (TOD) scheduling used with BAS systems?
TOD scheduling provides on/off times for equipment, which allows the BAS to operate the equipment at specific times of day and at its most optimal conditions.

What are the two types of connection configurations in a typical system?
The two types of connection configurations in a typical system are the series connection and the parallel connection.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

The control of equipment can be via a DDC (Direct Digital Control) or a central SCADA (Supervisory Control and Data Acquisition) system. A DDC unit is a digital controlling device, generally mounted locally on the equipment itself, or in the surrounding area, if the equipment is remote to the main controlling computer. The DDC provides the operator the capability of configuring and/or controlling the unit locally, rather than remotely. In this case, using the DDC on the equipment is generally referred to as manual operation of the unit. It is very common to enter this mode when performing maintenance repair activities onto the unit itself. SCADA is another term used for BAS systems where building-related equipment can be remotely controlled by a central computer. The SCADA systems provide the operator with the capability to control equipment remotely from a central room where other equipment is also being controlled, and data can be queried and processed for maintenance and troubleshooting purposes. The centralized SCADA/BAS is generally used during normal operating hours of the facility. It is important to produce a well-configured BAS system that will consider the planning of TOD (Time of Day) schedules for the different facility related equipment. TOD scheduling provides on/off times for equipment and system, and is essential when taking energy efficiency measures in a facility. This allows the BAS to operate certain equipment at certain times of the day when the equipment is used at its most optimal conditions. A typical example would be when the air conditioning system for a building Is under a plan of maximum efficiency operation during the peak hours of the day (6am to 10pm), and minimum operation at non-peak hours (10pm to 6am). Thus, an effective TOD schedule will control the AC system to meet the demands of the day and utilize the low usage of the night for maximizing energy cost savings activities or measures.