Building automation facts for kids

A building automation system (BAS) is like the brain of a modern building. It automatically controls many important systems in a building from one central place.

Think of it controlling things like:

• Heating, ventilation, and air conditioning (HVAC)
• Lights
• Window shades
• Security cameras and alarms
• Door access

The main goals of building automation are to make people inside the building more comfortable and to make the building run efficiently. This helps save energy, lowers costs, and makes the building safer.

A BAS is a type of distributed control system. This means it uses a computer network to connect many electronic devices. These devices work together to watch over and control the building's systems.

The BAS makes sure the building's temperature stays just right. It can turn lights on and off based on a schedule or if people are in a room. It also checks if systems are working well and sends alerts if something breaks.

Buildings with a BAS are often called "smart buildings." Most large buildings built after 2000 use a BAS. Many older buildings have also added these systems to save energy and money.

What is a Building Automation System?

A building automation system (BAS) is an electronic control system. It manages a building's heating, ventilation, and air conditioning (HVAC). Modern BAS can also control indoor and outdoor lights. They can even handle security systems and fire alarms. Basically, they control almost anything electrical in a building.

Older control systems were simpler. They lacked the flexibility and connections of today's smart systems.

How Smart Buildings Communicate

Smart buildings use special computer networks. These networks connect different controllers and devices. This allows them to "talk" to each other.

There are main "buses" or pathways that connect high-level controllers. These controllers then connect to smaller controllers and devices. They also connect to the user interface, which is how people interact with the system.

Many devices use open standards like BACnet or LonTalk. These standards help different devices work together. Modern systems also use SNMP to track events. This comes from how computer networks have worked for decades.

Devices can connect using wires like ethernet or RS-485. They can also use wireless networks. Newer systems use standards like IEEE 1905.1. This allows many different devices to connect, even if they use different types of wiring. This includes powerline networking (using electrical wires) and high-speed wireless networks like LTE and IEEE 802.11ac. They can also use ZigBee, which is a wireless standard for smart devices.

Some companies make their own special hardware for controllers. These might not work well with systems from other companies. But many modern systems allow devices from different makers to work together. This is often done using the SNMP.

How a BAS Senses and Controls Things

A building automation system uses different types of inputs and outputs to do its job.

Sensors: How the BAS Gathers Information

Sensors are like the eyes and ears of the BAS. They read different measurements:

• Analog inputs measure things that change gradually. Examples are temperature, humidity, and pressure sensors. These might use special wires or be wireless.
• Digital inputs tell the system if something is simply on or off. For example, a door contact switch can tell if a door is open or closed. A current switch can tell if electricity is flowing.
• Some digital inputs can count pulses over time. This is useful for measuring things like water flow.

There are also smart software systems that use digital sensors. They can figure out what appliances are running just by looking at the electrical patterns. This helps find problems early.

Controls: How the BAS Makes Things Happen

Controls are how the BAS tells devices what to do:

• Digital outputs control the speed or position of a device. For example, they can tell a variable frequency drive to speed up a motor slowly. Or they can open a valve a certain amount.
• Analog outputs turn things on or off. They can also send power to a device. For example, they can turn on parking lot lights when it gets dark. They can also open a valve by sending it power.
• Some analog outputs can send out pulses. This is used for things like energy meters that send data as a frequency of pulses.

The Brains of the Building: Controllers

Controllers are like small, special computers. They have inputs to read information and outputs to send commands. They come in different sizes for different jobs in a building.

• Inputs let a controller read things like temperature, humidity, and air flow.
• Outputs let the controller send signals to other devices.

There are three main types of controllers:

• Programmable Logic Controllers (PLCs)
• System/Network Controllers
• Terminal Unit Controllers

Terminal unit controllers are usually for simpler tasks. They might control lights or a single heating/cooling unit. They often have pre-set programs, so installers don't have to create new rules.

How a BAS Manages Occupancy

Occupancy is one of the main ways a building automation system operates. Other modes include "Unoccupied" (when no one is there) or "Morning Warmup."

• Occupancy mode usually follows a time schedule. In this mode, the BAS works to keep the building comfortable and well-lit. It can even control different areas (zones) of the building separately. So, one side of the building might have a different temperature setting than the other.
• A temperature sensor in each area sends information back to the controller. This helps the system deliver heating or cooling as needed.
• Morning Warmup happens before people arrive. The BAS tries to get the building to the right temperature just in time for occupancy. It uses outside weather and past experience to do this efficiently.
• Sometimes, people can manually "override" the system. For example, a button on a wall thermostat might turn on the system for a short time.
• Some buildings use occupancy sensors to turn on lights or adjust the temperature when people are detected.

Controlling Lights and Shades

Lighting

A building automation system can turn lights on, off, or dim them. This can be based on:

• The time of day.
• If people are in the room (using occupancy sensors).
• How much natural light is coming in (using photosensors).
• Timers.

For example, lights in a room might turn off 30 minutes after no motion is detected. A sensor outside can tell if it's dark and adjust lights in offices or the parking lot.

Lighting is also good for saving energy during "demand response" events. This is when the power company asks buildings to use less electricity. The BAS can dim or turn off lights to help.

Newer buildings use a system called Digital Addressable Lighting Interface (DALI). This allows lamps to be fully dimmed. DALI can also tell if a lamp or its ballast (a device that helps the lamp work) has failed.

Shading and Glazing

Window shades and special glass (glazing) are important for comfort. They affect how much light, sound, and heat enter a building. Automated shading systems control external or internal shades (like blinds) or even the glass itself.

These systems react quickly to changes outside (like sun and wind) and inside (like temperature and people's needs). They help control how much sunlight and heat enter the building. This saves energy and keeps people comfortable.

Dynamic Shading

Dynamic shading devices control daylight and solar energy. They adjust based on outdoor conditions and how much light is needed inside. Common examples include venetian blinds, roller shades, and louvers. They are often inside windows because they are easier to maintain.

Managing Air in the Building

Air Handlers

Most air handlers mix fresh outside air with air from inside the building. This means less heating or cooling is needed. A certain amount of outside air is always needed to keep the air healthy inside. To save energy and keep the air clean, "demand control ventilation" (DCV) adjusts how much outside air comes in based on how many people are in the building.

Sensors measure temperature in rooms and air ducts. Devices called actuators control hot and chilled water valves and air dampers. Fans turn on and off based on time, temperature, or air pressure.

Constant Volume Air-Handling Units (CAV)

These are less efficient. Their fans don't change speed. Instead, they open and close dampers and water valves to control temperature. They heat or cool by sending hot or chilled water to internal heat exchangers. One CAV usually serves several rooms.

Variable Volume Air-Handling Units (VAV)

These are more efficient. VAV units send pressurized air to "VAV boxes," usually one box per room. A VAV air handler can change the air pressure by changing the fan's speed using a variable frequency drive. The amount of air supplied depends on what the VAV boxes need.

Each VAV box supplies air to a small area, like an office. It has a damper that opens or closes based on how much heating or cooling that area needs. The more boxes that are open, the more air the VAV air-handling unit supplies.

Some VAV boxes also have hot water valves and a heater. These are often used for rooms on the outside of the building.

Controlling Air Temperature

Air handling units that serve many areas should automatically change the "discharge air temperature" (the temperature of the air they send out). This helps save energy for cooling, heating, and fans. For example, if it's cool outside, raising the supply-air temperature means less reheating is needed in the rooms.

Central Plant: The Building's Powerhouse

A central plant provides water for the air-handling units. This includes chilled water for cooling, hot water for heating, and condenser water for chillers. It might also have transformers and backup power. When managed well, these systems can help each other. For example, some plants make electricity when demand is high. They then use the heat from making electricity to heat water or power a chiller.

Chilled Water System

Chilled water is often used to cool a building's air and equipment. The chilled water system has chillers (large refrigerators) and pumps. Sensors measure the temperature of the chilled water. The chillers turn on and off to keep the water cold.

Chillers make cool water for cooling spaces. This chilled water then goes to cooling coils in air handling units or other cooling devices. Chilled water systems are often used in larger buildings. They can cool many areas from one chiller.

Condenser Water System

Cooling towers and pumps provide cool water to the chillers. This "condenser water" helps the chillers get rid of heat. Because the water supply to the chillers needs to be constant, fans on the cooling towers often use variable speed drives to control the temperature. Sensors measure the condenser water temperature.

Hot Water System

The hot water system provides heat to the building's air-handling units or VAV box heaters. It also heats water for sinks and showers. This system has boilers (heaters) and pumps. Sensors measure the hot water temperature. The boilers and pumps turn on and off to keep the hot water supply steady.

Using variable frequency drives (VFDs) on the building's water pumps can greatly reduce energy use. A VFD changes the frequency of electricity to the motor. This allows the motor to run slower and use much less energy. For example, if a motor runs at half speed, it might use only about 18% of the energy it would at full speed. This is because the relationship between speed and energy use is not a simple straight line. VFDs help pumps save a lot of energy, often reducing their use to about 15% of what it was before.

Alarms and Security in Smart Buildings

All modern building automation systems have alarm features. If a problem happens, the system needs to tell someone who can fix it. Notifications can be sent by email, text message, pager, phone call, or an audible alarm. For safety and record-keeping, systems log who was notified and when.

Alarms can notify someone right away. Or they might wait until several alarms happen, showing a more serious problem. For example, if a power outage causes many devices to shut down, the system should recognize this as one big problem, not hundreds of small ones. Some critical alarms will repeat until the problem is fixed.

Here are some common alarms:

• Temperature alarms: For rooms, supply air, or water temperatures.
• Pressure, humidity, and air quality sensors: These can tell if ventilation systems are failing or if there are harmful substances in the air.
• Filter alarms: Sensors on filters can tell if they are dirty and need changing.
• Status alarms: If a device like a pump is told to start but shows it's still off, this means there's a problem.
• Valve alarms: Some valves have switches to show if they have opened or closed.
• Carbon monoxide and carbon dioxide sensors: These detect if levels of these gases are too high, which could mean a fire or ventilation problem.
• Refrigerant sensors: These can detect leaks from cooling systems.
• Current sensors: These can find problems like slipping fan belts or clogged pumps.

Security systems can be connected to the building automation system. If there are occupancy sensors, they can also act as burglar alarms. For security, some detectors or cameras should have battery backup and wireless connections. This way, they can still work if power is cut or wires are disconnected.

Fire alarm systems are usually wired to override the building automation. For example, if a smoke alarm goes off, all outside air dampers might close to stop air from entering the building. An exhaust system might then isolate the fire. Similarly, electrical fault systems can turn off entire circuits for safety. Systems that burn fuel (like natural gas) also have their own safety overrides.

Good building automation systems understand these safety overrides. They don't send too many alerts. They also don't waste backup power trying to turn devices back on that safety systems have turned off. A well-designed BAS is often built around safety and fire systems.

Information Security

As building automation systems become more connected to the Internet of Things, they can become targets for hackers. Hackers might try to control parts of a building. For example, sensors could be used to watch people, and controls could open doors for intruders. Many companies and groups are working to make these systems more secure.

Room Automation

Room automation is a smaller version of building automation. It focuses on controlling systems within a single room.

A common example is in corporate meeting rooms or lecture halls. In these rooms, there are many devices:

• videoconferencing equipment
• video projectors
• lighting control systems
• public address systems

It would be very complicated to control all these devices manually. So, room automation systems use a touchscreen to control everything easily.

Images for kids

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  A diagram showing how different parts of a building automation system connect.

See also

In Spanish: Inmótica para niños