Building Management Systems (BMS) are widely used for efficient and effective control of building services. The Direct Digital Control (DDC) is an essential component of the BMS, as it provides accurate monitoring and control of HVAC systems, lighting, and other building services. In this article, we will discuss the major components of the DDC Panel and their types, functions, and uses in detail.
Processor: The processor is the brain of the DDC Panel, responsible for controlling and monitoring building systems. It receives inputs from field devices, processes the data, and sends appropriate outputs. The most commonly used processors in BMS Panels are Programmable Logic Controllers (PLCs) and Building Automation Controllers (BACs).
Modules: The modules are connected to the processor and provide various input/output (I/O) functions. There are different types of modules such as Analog Input modules, Analog Output modules, Digital Input modules, and Digital Output modules. These modules are available in universal types that can be used for any I/O function or dedicated types that are specifically designed for a particular function.
Control Transformer: The control transformer reduces the voltage supply to the safe operating level required for the DDC Panel components.
Terminal Block: The terminal block provides a secure connection for wiring between the components of the DDC Panel.
Relays: Relays are used for switching high power loads on and off. They act as an interface between the control system and the field devices.
Fuses: Fuses protect the DDC Panel from overcurrent due to faults in the field devices.
Power Supply Unit: The power supply unit converts the mains voltage into a low voltage DC power supply that is required by the DDC Panel.
Bus Connection Module: The bus connection module is used to connect the DDC Panel to other panels in remote locations.
Other components: Other components of the DDC Panel include surge protection devices, Isolation transformers, communication modules, and memory modules.
Language the processor understands:
The processor in the DDC Panel can understand different programming languages such as Ladder Logic, Function Block Diagram (FBD), Structured Text, and Instruction List.
Cable adaptor:
The cable adaptor used to connect the power supply with the module in another panel is called a Power over Ethernet (PoE) Adapter.
Types of I/O modules and universal modules:
As mentioned earlier, there are various types of I/O modules such as Analog Input modules, Analog Output modules, Digital Input modules, and Digital Output modules. In addition to these, universal modules are also available that can be used for any I/O function.
Types of cables used to connect the field devices to the I/O Modules:
Different types of cables are used to connect field devices to the I/O modules such as twisted pair cables, shielded cables, and unshielded cables.
Terminal block and its use:
The terminal block provides a secure connection for wiring between components of the DDC Panel. It allows easy maintenance and replacement of components in the panel.
Enclosure type of the DDC Panels:
DDC Panels are available in different enclosure types such as wall mount, floor mount, and free-standing enclosures. The selection of the enclosure type depends on the application and location of the panel.
Wire marker or labels:
Wire markers or labels help in identifying wires during maintenance and troubleshooting. It saves time and effort for the maintenance team and reduces the chances of errors during maintenance.
Connecting controllers with each other:
Controllers can be connected with each other through a daisy chain connection. RS-485 is a commonly used communication protocol for this purpose. The maximum distance allowed for the RS-485 connection is 1200 meters. A repeater is used to extend the distance beyond this limit.
In conclusion, DDC Panels are an essential component of Building Management Systems. Understanding their components, functions, and uses can help in efficient management and maintenance of building services.
What is a DDC Panel ?