Components of BMS

Components of BMS 

A Building Management System (BMS)—also known as a Building Automation System (BAS)—is a computer-based control system installed in buildings to monitor and manage the Mechanical, Electrical, and Electromechanical services. 

These services typically include:

·        HVAC (Heating, Ventilation, and Air-conditioning or all supply and exhaust fans, ACs etc.). 

·        Lighting control system. 

·        Fire alarm system. 

·        Firefighting system. 

·        Security control system. 

·        Lift control system. 

·        Pumping system. 

·        Water tanks level. 

·        Irrigation system. 

·        Electrical Energy meters.

·        Water Leak detection system.

·        Split units. 

·        VFD-Variable frequency drives. 

·        VRF/VRV-Variable refrigerant flow or volume (both are same but each term copyrighted by a different vendor) 

·        And any other system which has provision for BMS to control and monitor. 

The primary goal of a BMS is to ensure efficient, safe, and reliable building operations, while also optimizing energy consumption and reducing operational costs.

Architecture Overview

BMS systems are built using a layered architecture:

1. Field Layer

✓Sensors and actuators (temperature sensors, motion detectors, relays, etc.)

2. Control Layer

✓DDC (Direct Digital Controllers) that receive inputs and control outputs.

3. Supervisory Layer

✓Workstations or servers that provide the graphical user interface (GUI).

4. Enterprise Layer

✓Interfaces with other systems like EMS (Energy Management System), DCIM, CMMS, etc.

 

Typical BMS Layout
[ Sensors ] ↔ [ DDC Controller ] ↔ [ BMS Server/SCADA ] ↔ [ Operator Workstation ]

 

Major Components

🔸 1. Sensors: These devices gather real-time data from the environment and send it to controllers. Common types:

✓Temperature Sensor Measure air, water, or room temperature

✓Humidity Sensor Track moisture levels in the air

✓CO₂ Sensor Monitor air quality and occupancy

✓Water Quality Sensors is analyze chemicals, pH levels, and other water parameters for environmental management. 

✓Pressure Sensor Detect duct or chilled water pressure

✓Occupancy Sensor Detect human presence in rooms

✓Hall effect sensors are used for position detection and occupancy sensing, such as determining if a door or window is open or closed, or if a motorized shade is in a particular position.

✓Flow Sensor Monitor fluid movement in pipes

✓Light Sensor Detect ambient lighting

✓Air Quality Sensors is measure gases like carbon monoxide to control ventilation system

✓Smoke/Leak Detector Smoke, gas, water leak Fire systems, water leak detection

✓Electrical relay and contactor

✓Current Sensors monitoring instruments find utility in the measurement of the electric current

✓DPS Differential pressure switches for ventilation and air conditioning (not for fuel gases) are for filter, fan or air flow monitoring in air conditioning and ventilation systems,

✓Energy Meter is a device that measures and monitors electrical or thermal energy consumption within a building. The meters collect energy consumption data and transmit it to the BMS's controllers.

✓Digital Sensors report on/off status, such as door contact switches or flow switches, or send pulses for counting events like water flow.

✓Analog Sensors provide a continuous, variable output, like thermistors or 0-10V signals, for detailed measurements of temperature, humidity, or pressure.

Signal Type Description Used With

✓Analog 0–10V Voltage proportional to value Temperature, CO₂

✓Analog 4–20mA Current loop, more stable Pressure, level

✓Digital (Dry Contact) ON/OFF or pulse count Flow switches, alarms

✓Resistive (NTC/PT100) Resistance changes with temp Thermistors, RTDs

🔸 2. Actuators
Actuators execute commands from controllers to adjust mechanical operations.
Type Function
✓Valve Actuators Open/close water or air valves
✓Damper Actuators Control air flow in ducts
✓Relay Modules Turn on/off electrical loads

🔸 3. Controllers (DDC – Direct Digital Controllers)
✓Controllers process inputs from sensors and determine outputs to actuators.
✓Local controllers: Installed near equipment (e.g., AHUs, chillers)
✓Programmable: Logic can be customized per application
✓Real-time processing: Executes control loops continuously
✓Supports communication: Modbus, BACnet, or proprietary

Panel Element Description
✓DDC Controller Main logic unit
✓Terminal Blocks Wiring terminations
✓Circuit Breakers Protection for I/O modules
✓Relays and Contactors For switching loads (pumps, fans)
✓24VDC Power Supply Supplies power to controllers/sensors

🔸 4. Field Devices
Combination of input/output modules, power supplies, fuses, and interface terminals mounted inside control panels.
✓Analog Input (AI): e.g., 4-20mA, 0-10V sensors
✓Digital Input (DI): e.g., dry contact, flow switch
✓Analog Output (AO): e.g., control signals to valves
✓Digital Output (DO): e.g., relay signal to pump/starter

🔸 5. User Interface Devices
a) Operator Workstations
b) Touch Panels / Mobile Apps

🔸 6. Network Infrastructure
BMS requires stable communication between field devices, controllers, and servers.
Type Example
✓Serial RS-485 (Modbus RTU, BACnet MSTP)
✓Ethernet/IP BACnet/IP, Modbus TCP
✓Fiber Optic Backbone for large campuses
✓Wireless Wi-Fi, LoRaWAN, Zigbee (modern IoT)

🔸 7. Server & Database System
🔸 8. SCADA/GUI Software

Extra innings - Real-Time example for BMS System

Any modern-day building client provides huge specifications for BMS System,

Whereas here I am going to take simple requirement to monitor and control the sequence of Air Handling Unit. 

Let us see below the requirement of the client to monitor and control the sequence in BMS System.

Before we go detailed about how to design the BMS System for the requirement, let us see some basics components of the AHU-Air handling unit.

AHU is an HVAC system which consists of the duct, fan, filter, cooling coil, heating element, humidifier, sound attenuators, dampers, valves and many more to regulate the air into the room by heating, ventilation and conditioning to distributes the conditioned air through the building and returns it to the AHU and also called as centralised AC in modern-day building.

Duct – It is the collection of metallic tubes that interconnected and distributes the heated/cooled air to the required rooms.

To monitor the duct air temperature in fresh, return and supply duct. We have to install the duct temperature sensor in the duct.

Fan Motor– Blower is used to circulate the air from fresh and return duct to the supply duct.

This fan motor controlled and monitored by the separate electrical panel by the designed electrical circuit with the help of electrical relay and contactor and providing an option to BMS system to

On/Off the fan.

Monitor the fan running status.

Monitor the Fan motor overload fault status and many more.

Filter– It is one of the main components in AHU to prevent the dust and dirt particles from entering in the AHU.

When the AHU fan motor started, the fresh outside air supplied into the duct where filter components used to filter the dirty particles continuously and to monitor the filter extreme dirty condition.

DPS switch is used to install across the filter and provide signals to BMS,

when the filter gets dirty(technically DPS-Differential pressure switch will send the signal to BMS when the pressure reached more than pre-set across the filter, and this same function can be used to monitor the fan status.

Heating/Cooling element- It is used to cool or heat the water that entered in the coil so that air in the duct can be heated or cooled based on the user requirement.

Either heating or cooling water enters into the coils are controlled and monitored by valves on the pipe with the help of the valve actuator.

Dampers- An HVAC damper is a movable plate, located in the ductwork, that regulates airflow and directs it to areas that need it most.

Damper opening and closing position-controlled electrically with the help of damper actuators, and these actuators have terminal for control from BMS and terminal to monitor the feedback of position.

3 Cybersecurity Steps to Reduce Threats to your Electrical System

 3 Cybersecurity Steps to Reduce Threats to your Electrical System

When anyone mentions cybersecurity, you may automatically think they are referring to IT systems. That is because protecting IT networks – and their associated personal, financial, and other proprietary data – has been the responsibility of IT professionals for an exceptionally long time. But what about your operational technology (OT) infrastructures? Are they also at risk from cyberattacks? How can you protect them? In this post, we’ll discuss these questions, and three specific recommendations for protecting your electrical systems.

The electricity subsector cybersecurity Risk Management Process (RMP) guideline was developed by the Department of Energy (DOE), in collaboration with the National Institute of Standards and Technology (NIST) and the North American Electric Reliability Corporation (NERC).

OT Cyberattacks: An Increasing Threat

The Ponemon Institute emphatically states that, “Cyberattacks are relentless and continuous against OT environments.” In a survey of over 700 organizations from six countries they found that 50 percent had experienced a cyberattack against their OT infrastructure within the last two years that resulted in downtime. For large and critical operations, this can be devastating.

All you need to do is follow the news to see frequent examples of such attacks. For example, in early 2021, the fast action of a technician narrowly avoided the risk of thousands of people being poisoned due to a hacker gaining access to a Florida city’s water treatment plant. Going back a few years, a breach that came through the HVAC system caused international retailer Target to have 40 million credit and debit card accounts compromised, costing them $290 million.

 

The latter example is just one of many that show why building systems are now widely recognized as OT attack targets. The evolution toward smarter buildings is causing an explosion in the numbers of connected devices – already an estimated 200+ million in commercial buildings alone. With more devices comes more data that needs to be protected, but for facility and business management teams to extract the maximum value, data must be aggregated and shared across OT and IT systems.

This OT/IT interconnection means that a cyberattack on an OT system can:

·        Compromise operational safety or the health of building occupants

·        Impact productivity by taking down production lines or other equipment and processes; more about the relationship between Cybersecurity and Productivity.

·        Ultimately cause an IT threat by passing malware or a virus from the OT to IT infrastructure

The Attack Surface is Now Larger

Essentially, connected OT infrastructures have increased the ‘attack surface’ for hackers and, in many cases, have acted as an organization’s Achilles heel. Clearly, it is not enough anymore to focus attention only on protecting IT and data systems integrity. All organizations must ensure strong OT cybersecurity is in place.

But what OT systems are we talking about? Depending on your type of operation, these can include industrial automation systems (e.g. SCADA) and smart building systems like a building management system (BMS), building security, lighting systems, and the energy and power management system (EPMS) overseeing your facility’s electrical distribution. Navigant Research notes, “Cybersecurity issues are expected to grow in tandem with the digital transformation of real estate through intelligent building technologies.”

In this post, we will consider cybersecurity specifically for your EPMS and electrical distribution system. However, these recommendations and practices equally apply to other OT systems.

Connected Power Means Greater Vulnerability

Energy and power management systems are helping organizations boost efficiency and sustainability, optimize operating costs, maximize uptime, and get better performance and longevity from electrical assets. When combined with BMS, an EPMS can also help make the work environment healthier and more productive for occupants.

Enabling these EPMS benefits is a connected network of smart metering, analysis, control, and protection devices that share data continuously with onsite and/or cloud-based EPMS applications. The application provides extensive monitoring and analytics while providing mobile access to data and alerts to all facility stakeholders. Connection to the cloud also opens the door to expert power and asset advisory support that can augment a facility’s onsite team with 24/7 monitoring, predictive maintenance, energy management, and other services.

All these onsite, cloud, and mobile connections offer a potential target and entry for hackers so you can read our facility managers guide to building systems and cybersecurity.

 

Securing Your Electrical System: A Holistic Approach

A hacker only needs to find one ‘hole’ in one system, at one point of time, to be successful. What you need is a holistic approach to ensure that all potential vulnerabilities are secured. For new buildings, cybersecurity best practices should be a part of the design of all OT systems. For existing buildings, cybersecurity should be addressed when OT systems are starting to be digitized. For both scenarios, the following are three key considerations:

1. Seek Specialized, Expert Assistance

The priorities for IT systems are confidentiality, integrity, and availability. For OT, the top priorities are safety, resilience, and confidentiality. This means that OT security upgrades or problems need to be addressed in a different way from IT, with careful planning and procedures. For these reasons, you need to choose a cybersecurity partner who has proper OT experience, to help you comply with all relevant cybersecurity standards and best practices.

OT systems also use different communication protocols compared to IT systems, such as BACNet, Modbus, etc. If you had your IT team attempt to perform OT security system scans, those scanning tools might cause serious conflicts, risking an OT system shutdown.

Cyberthreats are also constantly evolving, so you should seek a partner who offers ongoing OT monitoring services, updates, system maintenance, and incident response. All of these should be available remotely.

2. Put the Right Controls in Place

An OT cybersecurity specialist will help audit your EPMS and electrical systems to assess the current vulnerabilities and risks, including the gaps in any procedures and protocols.

You and the specialist must determine how secure your electrical system needs to be. The IEC 62443 standard helps protect IoT-enabled OT systems by defining seven foundational requirements (e.g. access control, use control, availability, response, etc.), each of which are designated a security level. Increased security levels offer greater protection against more sophisticated attacks. Your cybersecurity partner will help you determine the level of security you need for each requirement.

An example of one technique for securing networked systems is to break up systems into ‘zones,’ with each secured individually. OT will be separated from IT, and within OT there may be further segregation. A special ‘demilitarized’ zone is typically included, which is a perimeter subnetwork that sits between the public and private networks for an added layer of security. This makes it harder for hackers to find a way in from one system or zone to another. Where required, connections between networks are provided by specially secured data ‘conduits.’

Your electrical system should also be physically secured, with no access by unauthorized personnel. This same strategy applies to EPMS communications network security by means of controlled, multi-tiered permission-based access.

3. Train your Staff

Many cyberattacks are successful because employees have caused unintended errors. It is important that your people become aware of, and vigilant against, cyberthreats. This includes giving your operations team specialized OT cybersecurity training.

This training will typically include multiple steps, including training all individuals to spot social engineering cues, such as phishing attempts or attempts to access protected areas using pretexting (i.e. someone pretending to be a vendor to gain access). This will also include establishing protocols around the use of passwords, multi-factor authorization, policies around WiFi access (e.g., guest network that remains isolated from OT networks), regular auditing of user accounts and permissions, etc.

While the horizontal cybersecurity framework provides a solid basis, specific characteristics of the energy sector such as the need for fast reaction, risks of cascading effects and the need to combine new digital technology with older technologies necessitate specific legislation.

Thanks to Felix Ramos & Khaled Fakhuri to write this article.