The Building Automation System (BAS) and the Building Management System are two distinct systems that interconnect to provide control, visibility, and awareness to the building operators. A BAS primarily consists of hardware devices, while the BMS is typically software with web-based capabilities that enable remote control and monitoring for those devices through a user interface (UI).

What is a Building Automation System (BAS)?

A Building Automation System, or BAS, is most commonly used in the realm of smart building technologies and direct digital controls (DDC) to denote the HVAC control system in large facilities and commercial buildings.

A BAS is a network of hardware devices, including supervisory devices, application controllers, sensors, actuators, relays, drives, etc., that work in unison to control the HVAC system. These devices interconnect and communicate with each other through communication protocols such as BACnet®, creating a network of controlling and monitoring devices that, as a whole, form what is known as the Building Automation System or BAS.

BAS: A network of controlling and monitoring devices

The term BAS is used to describe the network of controlling and monitoring devices in charge of the HVAC control system in large facilities. These HVAC systems require a network of controlling devices to ensure that the different components of the system, which are often physically distanced from each other, can operate in unison to maintain space comfort, air quality, and energy efficiency.

A Chilled Water System is a clear example of these large HVAC systems in commercial buildings. The chiller plant is physically separated from the air handling units (AHU), and similarly, the air handling units are distanced from the terminal units such as variable air volume unit boxes (VAV). This physical separation requires equipment and plant controllers to also be situated apart from each other. To facilitate communication and coordinated operation among these controllers, a network of interconnected devices is necessary, known as the Building Automation System or BAS.

What is a Building Management System (BMS)?

A Building Management System, or BMS, is a system used by building operators to supervise, monitor, and control several critical systems for overall business operation and efficiency, including building surveillance, access control, HVAC, utilities, etc., just to name a few.

Building Management Systems are most commonly software and web-based applications that enable the user interface (UI) for building operators to remotely access, view, and manage a specific system or multiple systems in a centralized location. There are many different BMS dedicated to various management functions. For instance, the software used to supervise security cameras does not need to be the same as the one used for space comfort and air quality control.

Building Management Systems not only provide monitoring and control over different systems but also enable special capabilities such as fault detection, data analytics, and artificial intelligence (AI) algorithms that improve system performance and efficiency, as well as awareness and time response to equipment failure events.

Relationship between BAS and BMS

The terms BAS and BMS are very commonly used interchangeably, primarily in the HVAC and Building Automation industries. This has created some confusion, leading people to believe they are the same thing, but they aren’t.

As we described before, the Building Automation System (BAS) is a network of controlling devices, while the Building Management System (BMS) is the front-end user interface application displaying system information that the operator can monitor and control accordingly. In other words, the BMS is the frontend, and the BAS is the backend, as the BMS reads data from the BAS and presents it in a way that is comprehensive to the building operators.

It’s important to note that a Building Management System (BMS) is a much broader term that encompasses more than just monitoring HVAC control devices. Any software application that enables the capability of monitoring and controlling systems in a building can be considered a Building Management System or BMS.

BAS vs. BMS: What causes confusion?

There are many Building Automation Systems (BAS) that include supervisory devices with web-based capabilities, enabling operators to remotely log into the supervisory interface and access a Building Management System (BMS) installed within the device. In this scenario, we can assert that the BMS is within the BAS, which likely contributes to the frequent interchangeability of both terms in the HVAC Control industry.

However, while utilizing supervisory devices to facilitate management capabilities is a viable solution for small sites, this BMS configuration has its limitations, such as memory, speed, and reliability. Consequently, it may be more aptly described as a building supervisory portal rather than a comprehensive BMS.

A typical BMS is usually installed on a powerful computer, such as a server or virtual machine. This configuration allows for enhanced cybersecurity capabilities, backup, reliability, capacity, and speed, enabling swift responses to user queries. This ensures efficient management of all equipment and integrated systems.

In Summary

Distinguishing between a Building Automation System (BAS) and a Building Management System (BMS) is vital in the HVAC and Building Automation industries. While the terms are often used interchangeably, they represent distinct aspects of the system.

The BAS, as the backbone, forms a network of controlling devices ensuring coordination for optimal building performance. In contrast, the BMS serves as the front-end user interface, enabling remote access and management.

The confusion arises from their interconnected nature, but recognizing that a comprehensive BMS extends beyond HVAC monitoring clarifies their roles. Understanding these distinctions is key to leveraging technology for efficient building management in an evolving landscape.