A Building Management System (BMS) is a computer-based control system installed in buildings that controls and monitors the building’s mechanical and electrical equipment such as ventilation, lighting, power systems, fire systems, and security systems. A BMS consists of software and hardware; the software program, usually configured in a hierarchical manner, can be proprietary, using such protocols as C-bus, Profibus, and so on. Vendors are also producing BMSs that integrate using Internet protocols and open standards such as DeviceNet, SOAP, XML, BACnet, LonWorks and Modbus.
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A BMS is most common in a large building. Its core function is to manage the environment within the building and may control temperature, carbon dioxide levels and humidity within a building. As a core function in most BMS systems, it controls heating and cooling, manages the systems that distribute this air throughout the building (for example by operating fans or opening/closing dampers), and then locally controls the mixture of heating and cooling to achieve the desired room temperature. A secondary function sometimes is to monitor the level of human-generated CO2, mixing in outside air with waste air to increase the amount of oxygen while also minimising heat/cooling losses.
Systems linked to a BMS typically represent 40% of a building's energy usage; if lighting is included, this number approaches 70%. BMS systems are a critical component to managing energy demand. Improperly configured BMS systems are believed to account for 20% of building energy usage, or approximately 8% of total energy usage in the United States.
As well as controlling the building's internal environment, BMS systems are sometimes linked to access control (turnstiles and access doors controlling who is allowed access and egress to the building) or other security systems such as closed-circuit television (CCTV) and motion detectors. Fire alarm systems and elevators are also sometimes linked to a BMS, for example, if a fire is detected then the system could shut off dampers in the ventilation system to stop smoke spreading and send all the elevators to the ground floor and park them to prevent people from using them in the event of a fire.
Building Management Systems have been employed for as long as commercial buildings have existed, whether this be through manpower loading coal into coal fired boilers or opening water pipe valves manually with the use of a handle so to enable heated water to flow through a radiator circuit. However, "BMS" as a phrase, is relatively new, the concept being introduced in the early 1970s (the terms BAS-building automation system, and EMS-energy management system are also used); the phrase has only really existed since the introduction of complex electronic devices that are capable of retaining data for the purposes of managing services such as power, lighting, heating and so on. It was the advent of the "modem", or "modulator-demodulator" which allowed analog signals to be digitized so that they could be communicated over long distances with a high degree of accuracy that spurred the development and deployment of modern BMSs. The Powers 570 was an example of such a system. Developed and marketed by Powers Regulator Company (later purchased by Siemens), it was deployed into the market in May 1970, as the model number suggests.
Before the modern, computer-controlled BMSs came into being, various electromechanical systems were in use to control buildings. Many facilities management offices had panels consisting of manual switches or more commonly, lights showing the status of various items of plant, allowing building maintenance staff to react if something failed. Some of these systems also include an audible alarm. Advancements in signal communications technology have allowed the migration of early pneumatic and "home run" hard wired systems, to modems communicating on a single twisted pair cable, to ultra fast IP based communication on "broad band" or "fiber optic" cable.
The three basic functions of a central, computer-controlled BMS are:
the building’s facilities, mechanical, and electrical equipment for comfort, safety, and efficiency.