Building automation glossary
The terms controls contractors use every day, defined in plain words, with links to the guides that put them to work.
- Network riser diagram
- A network riser diagram is the BAS drawing that shows every controller, router, switch and network on a job, floor by floor, and how they connect. Each panel is labeled with its network address and BACnet device instance. Controls contractors often call it the network diagram; specs usually say riser.
- Points list
- A points list, also called an I/O list or points schedule, is the table of every input and output each BAS controller handles: point name, type (AI, AO, BI, BO or software value), the field device it reads or drives, and its location. It sizes the controllers and drives programming, graphics and checkout.
- Submittal
- A BAS submittal, or controls submittal, is the package the controls contractor sends to the engineer for approval before installation: control schematics, wiring diagrams, network riser, points lists, sequences of operation, schedules and product data. It is also called shop drawings or control drawings.
- Sequence of operations
- A sequence of operations (SOO) is the written description of how a building system is controlled: its modes, start and stop conditions, setpoints and control loops, alarms and safeties. It is part of the BAS submittal and should refer to the exact point names of the points list.
- As-built drawings
- As-built drawings, or record drawings, are the submittal drawings updated to match what was actually installed: final riser, points lists, wiring and device locations. They are delivered at closeout with test reports and the O&M manual, and they are what the owner and service technicians rely on for years.
- BACnet/IP
- BACnet/IP is BACnet carried over standard Ethernet and IP networks. In most BAS designs it forms the backbone that links building controllers, operator workstations and large equipment, while field controllers sit on MS/TP trunks connected through routers. Its default UDP port is 47808.
- BACnet MS/TP
- BACnet MS/TP (master-slave/token-passing) is the BACnet data link that runs over RS-485 twisted pair, used for field controllers on each floor or system. Master devices pass a token to take turns on the wire. Each trunk connects to the IP backbone through a router.
- Device instance
- The BACnet device instance is the number that identifies a device across the whole BACnet internetwork, like a numeric name the front end uses to find it. It ranges from 0 to 4,194,302 (4,194,303 is a wildcard) and must be unique on the internetwork, whatever trunk the device sits on.
- MS/TP MAC address
- The MS/TP MAC address is a device's address on its RS-485 trunk: 0 to 127 for master devices, up to 254 for slaves. It must be unique on that trunk only. Many specs require sequential addresses starting at 0, with Max Master set to the highest master address.
- BACnet object types
- BACnet represents each point as an object. Analog Input (AI) and Binary Input (BI) are read from sensors and contacts, Analog Output (AO) and Binary Output (BO) drive actuators and relays, and Analog, Binary and Multi-state Values (AV, BV, MSV) are software points such as setpoints and modes.
- I/O point
- An I/O point is a physical input or output wired to a BAS controller terminal: a sensor or contact the controller reads (input) or an actuator or relay it drives (output). Counting I/O points by type, per controller, is how controllers are sized; software points are counted separately.
- DDC controller
- A DDC (direct digital control) controller is the field device that reads sensors, runs the control sequence in software and drives actuators for a piece of equipment or a system: an air handler, a VAV box, a plant. It talks to other controllers and the front end over a network such as BACnet.
- Supervisory controller
- A supervisory controller sits between field controllers and the front end: it gathers their trunks, runs schedules, trends and alarms for the group, and serves data to the operator workstation. In Niagara systems it is commonly called a JACE. Some owners require a separate riser for each one.
- Modbus
- Modbus is a simple master/slave protocol, over RS-485 (Modbus RTU) or Ethernet (Modbus TCP), widely used by meters, variable frequency drives and packaged equipment. In a BAS it is usually integrated through a supervisory controller or gateway that maps Modbus registers to BACnet points.
- PICS
- A PICS (Protocol Implementation Conformance Statement) is the manufacturer's document listing which BACnet services, object types and data links a device supports. Specs often require a PICS for every DDC controller in the submittal, and BTL listing shows the device was tested.
- BAS vs BMS
- BAS (building automation system) and BMS (building management system) usually mean the same thing: the network of controllers and software that runs a building's HVAC and related systems. BAS is the common term in the United States, BMS in the United Kingdom and many other countries. EMS often refers to energy-focused systems.
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