Main Parts of Building Automation Systems

Main Parts of Building Automation Systems

Building automation is a programmed, computerized, "intelligent" network of electronic devices that monitor and control the different systems of a building such as HVAC, security, fire, or lighting systems. The intent is to create an intelligent building and reduce energy and maintenance costs.

 

 

 Controller

The controller is normally one or more programmable logic controllers (PLC), often with custom programming. PLCs come in a wide range of sizes and capabilities to control devices that are common in buildings. Usually the primary and secondary buses are chosen based on what the PLCs provide.

Most PLCs provide general purpose feedback loops, as well as digital circuits.

    Occupancy Sensors

The operation of a building is typically based on occupancy. Occupancy is defined by time of day schedules to show when the building's systems are most likely in need of operation. Override is possible through different means. Some buildings can sense occupancy in their internal spaces by an override switch or sensor.

    Lighting System

Lighting is another automated service that can be turned on and off with a building automation system based on time of day, or the occupancy sensors and timers. Operating times can be set by individual tenants within the building. 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.

  Heating ,Ventilation and Air Conditioning (HVAC) System

Climate control in buildings is an important automated service that can save a lot of energy and thus money if the right technologies and design were used. For example, the heating system can be turned down automatically during the night or switched off completely when windows are open during the day. The building also "considers" its occupants. The night-time heating control temperature is not simply reduced on a timer basis like in conventional systems, it is automatically adjusted to the actual utilization levels and temperatures can automatically be adjusted to the actual weather conditions. The indoor air quality can be monitored via suitable sensors, and the climate can be adjusted as required.  

  Alarm and Security Systems

Many building automation systems have alarm capabilities. It can be programmed to notify someone if an alarm is detected. Notification can be through a computer, pager, Mobile phone or audible alarm.

-                Common temperature alarms are Space, Supply Air, Chilled Water Supply and Hot Water Supply.

-                Differential pressure switches can be placed on the filter to determine if it is dirty.

-                Status alarms are common. If a mechanical device like a pump is requested to start, and the status input indicates it is off. This can indicate a failure.

-                Some valve actuators have end switches to indicate if the valve has opened or not.

-                Carbon monoxide and carbon dioxide sensors can be used to alarm if levels are too high.

At sites with several buildings, momentary power failures can cause hundreds or thousands of alarms from equipment that has shutdown. Some sites are programmed so that critical alarms are automatically re-sent at varying intervals. For example, a repeating critical alarm (of an uninterruptible power supply in 'by pass') might resound at 10 minutes, 30 minutes, and every 2 to 4 hours there after until the alarms are resolved.

Security systems can also be interlocked to a building automation system. If occupancy sensors are present, they can also be used as burglar alarms.

Fire and smoke alarm systems can be hard-wired to override building automation. For example: if the smoke alarm is activated, all the outside air dampers close to prevent air coming into the building, and an exhaust system can isolate the alarmed area and activate an exhaust fan to move smoke out of the area. Life safety applications are normally hard-wired to a mechanical device to override building automation control.