Building automation
Building automation systems, also known as building management system or building energy management system, is the automatic centralized control of a building's HVAC, electrical, lighting, shading, access control, security systems, and other interrelated systems. Some objectives of building automation are improved occupant comfort, efficient operation of building systems, reduction in energy consumption, reduced operating and maintaining costs and increased security.
BAS functionality may keep a buildings climate within a specified range, provide light to rooms based on occupancy, monitor performance and device failures, and provide malfunction alarms to building maintenance staff. A BAS works to reduce building energy and maintenance costs compared to a non-controlled building. Most commercial, institutional, and industrial buildings built after 2000 include a BAS, whilst older buildings may be retrofitted with a new BAS.
A building controlled by a BAS is often referred to as an "intelligent building", a "smart building", or a smart home. Commercial and industrial buildings have historically relied on robust proven protocols while proprietary protocols were used in homes.
With the advent of wireless sensor networks and the Internet of Things, an increasing number of smart buildings are resorting to using low-power wireless communication technologies such as Zigbee, Bluetooth Low Energy and LoRa to interconnect the local sensors, actuators and processing devices.
Almost all multi-story green buildings are designed to accommodate a BAS for the energy, air and water conservation characteristics. Electrical device demand response is a typical function of a BAS, as is the more sophisticated ventilation and humidity monitoring required of "tight" insulated buildings. Most green buildings also use as many low-power DC devices as possible. Even a passivhaus design intended to consume no net energy whatsoever will typically require a BAS to manage heat capture, shading and venting, and scheduling device use.
Characteristics
Building management systems are most commonly implemented in large projects with extensive mechanical, HVAC, and electrical systems. Systems linked to a BMS typically represent 40% of a building's energy usage; if lighting is included, this number approaches to 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.In addition to controlling the building's internal environment, BMS systems are sometimes linked to access control or other security systems such as closed-circuit television and motion detectors. Fire alarm systems and elevators are also sometimes linked to a BMS for monitoring. In case a fire is detected then only the fire alarm panel could close dampers in the ventilation system to stop smoke spreading, shut down air handlers, start smoke evacuation fans, and send all the elevators to the ground floor and park them to prevent people from using them.
Building management systems have also included disaster-response mechanisms to save structures from earthquakes. In more recent times, companies and governments have been working to find similar solutions for flood zones and coastal areas at-risk to rising sea levels. Self-adjusting floating environment draws from existing technologies used to float concrete bridges and runways such as Washington's SR 520 and Japan's Mega-Float.
Types of inputs and outputs
Sensors
Analog inputs are used to read a variable measurement. Examples are temperature, humidity and pressure sensors which could be thermistor, 4–20 mA, 0–10 volt or platinum resistance thermometer, or wireless sensors.A digital input indicates a device is on or off. Some examples of digital inputs would be a door contact switch, a current switch, an air flow switch, or a voltage-free relay contact. Digital inputs could also be pulse inputs counting the pulses over a period of time. An example is a turbine flow meter transmitting flow data as a frequency of pulses to an input.
Nonintrusive load monitoring is software relying on digital sensors and algorithms to discover appliance or other loads from electrical or magnetic characteristics of the circuit. It is however detecting the event by an analog means. These are extremely cost-effective in operation and useful not only for identification but to detect start-up transients, line or equipment faults, etc.
Occupancy sensors detect the presence, number, and sometimes location of people in a space to enable demand-controlled systems for lighting, HVAC, and energy management. Traditional examples include passive infrared, ultrasonic, and CO2-based detectors, but advanced systems use low-resolution thermal imaging or area sensors to provide zone-level accuracy without capturing identifiable images, ensuring privacy compliance. These sensors output analog heat signatures or digital counts that integrate with building management systems via protocols like BACnet or wireless IoT networks, reducing energy use by up to 40% through precise ventilation and lighting control.
Controls
Analog outputs control the speed or position of a device, such as a variable frequency drive, an I-P transducer, or a valve or damper actuator. An example is a hot water valve opening up 25% to maintain a setpoint. Another example is a variable frequency drive ramping up a motor slowly to avoid a hard start.Digital outputs are used to open and close relays and switches as well as drive a load upon command. An example would be to turn on the parking lot lights when a photocell indicates it is dark outside. Another example would be to open a valve by allowing 24VDC/AC to pass through the output powering the valve. Analog outputs could also be pulse type outputs emitting a frequency of pulses over a given period of time. An example is an energy meter calculating kWh and emitting a frequency of pulses accordingly.
Infrastructure
Controller
Controllers are essentially small, purpose-built computers with input and output capabilities. These controllers come in a range of sizes and capabilities to control devices commonly found in buildings, and to control sub-networks of controllers.Inputs allow a controller to read temperature, humidity, pressure, current flow, air flow, and other essential factors. The outputs allow the controller to send command and control signals to slave devices, and to other parts of the system. Inputs and outputs can be either digital or analog. Digital outputs are also sometimes called discrete depending on manufacturer.
Controllers used for building automation can be grouped in three categories: programmable logic controllers, system/network controllers, and terminal unit controllers. However an additional device can also exist in order to integrate third-party systems into a central building automation system.
Terminal unit controllers usually are suited for control of lighting and/or simpler devices such as a package rooftop unit, heat pump, VAV box, fan coil, etc. The installer typically selects one of the available pre-programmed personalities best suited to the device to be controlled, and does not have to create new control logic.
Occupancy
Occupancy is one of two or more operating modes for a building automation system; unoccupied, morning warmup, and night-time setback are other common modes.Occupancy is usually based on time of day schedules. In occupancy mode, the BAS aims to provides a comfortable climate and adequate lighting, often with zone-based control so that users on one side of a building have a different thermostat than users on the opposite side.
A temperature sensor in the zone provides feedback to the controller, so it can deliver heating or cooling as needed.
If enabled, morning warmup mode occurs prior to occupancy. During morning warmup the BAS tries to bring the building to setpoint just in time for occupancy. The BAS often factors in outdoor conditions and historical experience to optimize MWU. This is also referred to as optimized start.
Some buildings rely on occupancy sensors to activate lighting or climate conditioning. Given the potential for long lead times before a space becomes sufficiently cool or warm, climate conditioning is not often initiated directly by an occupancy sensor.
Lighting
can be turned on, off, or dimmed with a building automation or lighting control system based on time of day, or on occupancy sensor, photosensors and timers. One typical example is to turn the lights in a space on for a half-hour since the last motion was sensed. A photocell placed outside a building can sense darkness, and the time of day, and modulate lights in outer offices and the parking lot.Lighting is also a good candidate for demand response, with many control systems providing the ability to dim lights to take advantage of DR incentives and savings.
In newer buildings, the lighting control can be based on the field bus Digital Addressable Lighting Interface. Lamps with DALI ballasts are fully dimmable. DALI can also detect lamp and ballast failures on DALI luminaires and signals failures.