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Chapter 18

Chapter 18. HVAC Control Systems Building Automation System Installation, Wiring, and Testing. Building Automation System Installation and Wiring. Building BAS Installation requires: 1. Proper controller mounting 2. Power supply selection 3. Network configuration

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Chapter 18

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  1. Chapter 18 HVAC Control Systems Building Automation System Installation, Wiring, and Testing

  2. Building Automation System Installation and Wiring • Building BAS Installation requires: 1. Proper controller mounting 2. Power supply selection 3. Network configuration 4. Testing techniques

  3. BAS Installation & Wiring • All BAS controllers should be wired in accordance with the National Electric Code (NEC) • Manufacturer recommendations should followed regarding testing and diagnostic procedures.

  4. Controller Mounting • Proper mounting is necessary to prevent controller damage. • Controller mounting methods vary from manufacturer to manufacturer. • In many applications the controller can be mounted in the existing pneumatic control panels. • Many manufacturers recommend DIN rail mounts. • DIN rail is a flat mounting rail that is attached to a control panel.

  5. Controller Mounting Requirements • BAS mounting requirements vary due to the wide range of manufacturers. • Exterior mounted control panels require a panel to which can protect against weather damage. • Many BAS are equipped with an operator interface that provides maintenance personnel with the ability to view controller functions and status. • Operator interfaces require installation 60” above the finished floor. • Operator interfaces are positioned in areas away from view, to prevent tampering. • Proper sizing of control panels are mandatory. • A location should be selected carefully as to reduce the conductor runs as much as possible.

  6. Common BAS Controller Mounting • Separate BAS controller conductors and power conductors by at least 1’. • Wire BAS controller connections using copper conductors of 18-gauge to 24-gauge. • Run network field conductors and line-voltage conductors and line voltage conductors of 30 VAC or higher in separate conduits.

  7. Controller Power Supplies • The most common power supply for BAS is a 120 VAC to 24 VAC step-down transformer. • Minimum wire size for BAS controller supply is 18-gauge, stranded, copper with a ground. • BAS controller power supplies use plug in plastic connectors or spade terminations.

  8. Power Supply Sizing • In most cases the BAS controller manufacturer recommends sizing for power supplies. • Size can be determined by adding the power requirements of the components. • A 100 VA transformer is the single largest transformer used in a BAS.

  9. Building Automation Systems Most buildings about 90% have only one primary desktop PC, have only one front-end. BAS changes may be temporary or permanent. New points can be added, old points deleted, and reconfigure system based on operator access levels.

  10. Controller Power Supply Isolation • Power supply isolation from ground is necessary to prevent ground loops, which cause improper controller operation. • Ground loop is a circuit that has more than one point connected to earth ground, with a voltage potential difference between 2 ground points can be high enough to produce a circulating current in the ground system.

  11. Controller Power Supply Polarity • Correct transformer polarity is necessary because the sensors and outputs are designed to operate properly with the correct polarity. • The 2 leads are labeled 24 VAC and common and should be properly connected.

  12. Package Unit Power Supplies • Package units such as rooftops and heat pumps have a built in power supply. • These built in power supplies are often used to power BAS controllers. • Isolation of the transformer should also be checked to ensure proper grounding. • A ground connected transformer cause the controller device to become grounded which can cause damage to the controller and the operator interfaces connected to the controller.

  13. Sharing Controller Power Supplies • In some buildings larger transformers can power multiple controllers. • The use of one transformer eliminates the need for multiple small transformers. • Is often recommended when multiple controllers are located very close together. • The disadvantage of sharing a power supply between multiple controllers is if the transformer fails multiple controllers fail.

  14. Controller On-board Batteries • BAS have an onboard battery for retention of memory and clock functions. • The battery is normally disconnected during shipping to prevent discharging of the battery.

  15. Communication Network Wiring • The network wiring allows controllers and other BAS devices to communicate with each other. • The information that is transmitted across the network may include the sharing of temperatures, time scheduling information, and alarm

  16. Conductor Type • The RS-485 communication standard requires a 2-conductor shielded cable or 3-conductor twisted shielded cable. • The minimum conductor size for BAS controllers is 22-gauge. • A 20 or 18-gauge conductor is recommended over 22-gauge because the possibility of wire kinking. • Color coding is recommended to ensure that the correct conductors are terminated in the correct position on the controller. • The RS-485 communication port comes standard polarity-sensitive.

  17. Shielding and Grounding • Shielding reduces the effects of electromagnetic interference on communication network wiring. • Electromagnetic interference is are caused by the operation of large motors, compressors, high voltage wiring, and lighting loads restrictions. • Electromagnetic interference is reduced by keeping communication network wiring away from large motors, compressors, high-voltage wiring.

  18. Optoisolation • It is communication method in which controllers use photonic components to prevent communication problems. • Is communicated through hard wired runs. • The binary (0 or 1) information transmitted is converted to an optical signal that is processed by the controller. • The BAS controller is isolated from the controller is isolated from the communication network because there is no physical connection between them, reducing or eliminating communication problems.

  19. Network Configurations • Daisy chain network configuration – multiple controllers are connected in series. Chains together a multiple number of BAS controllers and avoids using wiring splices. • Multi-drop network configuration – controllers are connected to the network that runs throughout a building and spliced drops are made for each controller. • Star network configuration – communication network cables run from the center out to the controllers.

  20. Network Addressing • It is a unique number assigned to each BAS controller. • This is done using a set of dip switches • 1,2,4,8,16,32,64,& 128.

  21. Input & Output Wiring • Input wiring brings information into the BAS either analog (incremental) or digital (ON/OFF). • Output wiring are take a control signal from the controller t a controlled device. • Peripheral devices are connected to a PC and perform a specific function. • Serial device transmits one bit of information (0 or 1) at a time. • Parallel device transmits multiple bits of information (0s or 1s) at a time. • Dumb terminal is a display monitor and keyboard with no processing capabilities.

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