What is a BMS?

Let’s take a high-rise building for example. The building will have mechanical, electrical and plumbing equipment. The mechanical equipment could be chillers, chilled water pumps, water heaters. Ventilation systems may include air handling units, fans etc. The electrical equipment may include escalators, lighting, electrical panels etc. This equipment will work standalone without any coordinated functionality. For example, to provide comfort in the building, the chiller should maintain the temperature at a certain degree. However, without a coordinated system, it is very difficult to manage all these systems manually. This is where BMS comes into action. BMS connects all these equipment in a centralized manner. The BMS controls, monitors, and optimizes these MEP equipment using hardware and software components. It is a package of Intelligent microprocessor-based controllers which connects directly to the equipment at a field level. The Controller sends the data to a management system where the data taken from the field equipment are translated into a Graphical User Interface (GUI) format.

Layers of BMS

The BMS provides comfort to building’s occupants, energy savings to the client and easier troubleshooting opportunities to the building operator. The BMS comprises of three main levels. The first one is the ‘Field Level’. This level refers to sensors, instruments, valves, actuators, thermostat, and IO modules etc. This level plays an important role in the Building Management System as the actions taken by the BMS is purely based on the inputs received from this level.

Next is the ‘Automation Level’. This can be referred to as the brains of the Building Management System. It consists of compact or modular DDC controllers. The DDC processes the inputs from the field devices and takes action to provide comfort to the building occupants and safety/security to the building equipment. These DDCs are freely programmable and can be connected to a handheld operator terminal that controls or monitors the field equipment at the Field Level without the requirement of any management system.

Next is the ‘Management Level’. The Management Level provides an interactable user interface to the Building Operator. It displays all the information taken from the Field Level by the controllers in a graphical user interface format. The Management Level can either be a PC or an HMI (Human Machine Interface). The Management Level can also send data via text or email in case of any critical alarms. The Field Level sensors and devices are connected to the Automation Level via hardwired connections, typically with a single pair cable. The operator terminal can be connected either via a bus cable or a standard ethernet cable. The Automation Level is connected to the Management Level via BACnet/IP protocol with the use of building structural cable networks.

Let’s discuss the Enterprise Level from the diagram later.

Communication protocols

Let’s investigate the communication protocols being used in the BMS. The most used protocol is BACnet (Building Automation Control network) protocol which is developed and managed by ASHRAE. It is an open protocol for the BMS where different BMS can be integrated. The next widely used protocol is LON Talk (Local Operating Network). It is widely used in low bandwidth applications. Next is Modbus, which is a serial communication protocol which uses Master/Slave Technology. This is a very old protocol, which has been used in PLCs since 1979. Other commonly used communication protocols are BACnet over Ethernet/IP, BACnet over LON, BACnet over MSTP, Modbus via RS-485, Modbus via RS-232, Modbus via TCP/IP.

Features of BMS

The BMS has many features which makes it an important system in building comfort and safety applications. The first one is the Graphical User Interface (GUI). All BMS provide a Graphical User Interface which represents a 2D or 3D view of the equipment. It also displays the sensors installed in the equipment. The most important feature of the BMS is Alarm Management Functionality. BMS provide a variety of alarm management functions. It is also possible for the BMS to send alarm information to an external program such as a Maintenance Management System (MMS) to generate work orders based on the alarm descriptions.

If the equipment is performing effectively, the BMS can provide the trend management functionality. It displays raw values in a time-based graph. These graphs can be exported into an Excel format for analysis. Since the BMS is also referred to as an Energy Management System (EMS), it provides functionality to control the equipment based on time. The Time Scheduler lets the operator decide when to turn ON and turn OFF the equipment.

The AHU serving the office can be programmed to turn ON only during the work hours. For example, from 7 am to 6 pm, and from 6 pm till next day 7 am, the AHU will be switched OFF to save energy. This is very helpful in many cases where the equipment can be configured to turn off when there is no occupancy in the building.

BMS History

Let’s get to know about the history of BMS a little bit. In the 1880s, Warren Johnson (the founder of Johnson Controls) patented the electric tele-thermoscope (now known as the thermostat). It is a bi-metal coil with a mercury switch that is used to alert the fireman to open/close the heating damper.

Late Warren Johnson developed his thermostat into a multi zone temperature control system using pneumatic controls. The pneumatic control uses compressed air to open/close pneumatic control valves or open/close air dampers. It was widely used in the building controls till the 1960s. From the 1970s, the pneumatic controls were replaced by electric controls and the building controls evolved into building automation controls. Now building automation control uses DDCs (Direct Digital Controllers) with relays to control the HVAC (Heating, Ventilation, and Air Conditioning) equipment.

In today’s world, the Building Management System is not only used in HVAC applications but also used to integrate various building systems into one and plays an important role in smart cities and building energy efficiency. It also saves operation costs for the building owner.

With the ability to finetune the system, a BMS increases the comfort of the building’s occupants and the efficiency of the equipment. It also improves building security and equipment safety with the ability to alert immediately in case of any abnormalities. With its ability to transfer the data to a Maintenance Management System, a BMS increases staff productivity and performance.

In the construction industry across the world, the Building Management System is also referred to as IBMS, BAS, BACS, EMS etc. Let’s clarify these terms.

IBMS (Integrated Building Management System)

When multiple third-party systems such as fire alarms, access controls, lighting controls, and parking management systems etc., are integrated with the Building Management System, it is referred to as an Integrated Building Management System. This allows the building operator to have a centralized control of all the systems from one place.

BAS (Building Automation System)

This is a standalone system without any management functionality, typically with a DDC control panel and a handheld operator terminal.

BACS (Building Automation Control System)

This is similar to the Building Management System, but in some cases PLC controllers are used with SCADA systems.

EMS (Energy Management System)

When additional energy management functions are used in the BMS, it is referred to as an Energy Management System. Such features are used in Green Building applications.

How IoT comes into play?

One of the biggest issues with traditional BMS products is that most use proprietary systems that are specific to a single manufacturer. This means you’ve got to stick with that manufacturer when you need to upgrade your system and use them for service or repairs. But the story is different with an IoT-based BMS. This game-changing technology can seamlessly connect to a wide variety of hardware types and manufacturers. It is designed to be “friendly” and “play well with others”. This provides customers with more choices and avoids vendor lock-in. IoT sensor data can be forwarded to the respective BMS server leveraging open interfaces (e.g., MQTT, REST API). This enables automated execution of relevant workflows like intuitive equipment reconfiguration, activation or shutdown, maintenance scheduling, or alert triggers. Recently BACnet protocol supported IoT gateways introduced to market, and it helps to integrate IoT cloud platforms with existing BMSs. Therefore, it will extend existing BMSs by adding an Enterprise Layer which can consolidate all systems.

In the past, BMS products had a steep learning curve. Their clunky user interfaces (UI) often meant hours of training, or worse; that a specialized technician had to be called to implement a change. An IoT-enabled BMS solution is intuitive, responsive, and simple. In fact, it is so simple that it requires little to no training. It will make building control accessible to everyone, regardless of expertise or experience, with an IoT-based BMS solution which is optimized for mobile devices. There is no longer a need to be present in the building, dial in, or access a special computer. So, whether you’re at work, at home, or somewhere in between, you’ll always have 24/7 access.

Traditional BMS products are expensive. A BMS that utilizes leading-edge IoT technology has less hardware and is easier to install. That saves money on the front end. It can also significantly reduce the time that facility operators spend in support of their buildings, saving money and allowing staff to be more productive. In fact, operators with an advanced BMS can expect a sizable improvement in overall efficiency, including energy, maintenance, and other recurring costs.

 – Written by Randika Silva.

Cover Picture Source : pixabay.com