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A Guide to Understanding Building Management System Protocols

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Brian Cline

For sensors, actuators, and controllers to function correctly in a building management system (BMS), a common method of data understanding is vital. Communication protocols describe the rules and formats through which data should be transferred over the interconnected network of sensors, actuators, and controllers. The data captured by sensors gets relayed to controllers that manipulate the system through actuators to the required endpoints. A communication protocol lets multiple device manufacturers make sensors, controllers, and actuators "work” together sharing data so an intelligent, actionable outcome can be achieved.

By exploring the several types of building management system protocols used by manufacturers, you can better understand the options available for your smart building.

Building Management System Protocols — An Overview

The choice of communication protocol to be used in a building management system depends on the equipment and control elements that are installed, and the level of flexibility needed. Some of the major classifications of building management system protocols include:

Opensource

 

Open Protocol

Open communication protocols are independent of any hardware or software. The communication rules are publicly available and are suitable for a wide range of BMS applications. Open protocols allow for easy integration of devices from multiple manufacturers into building management systems. Most, if not all open protocols abide by a standard that some organization or industry group set, like BACnet or Modbus. When manufacturers abide by the “open” protocol rules, it allows for interoperability of system components like sensors, controllers, and actuators.
ClosedSource

 

Proprietary Protocol

The data structure of a device using proprietary protocols is not shared by its manufacturer, making the BMS “locked down,” also known as a closed system. Such systems are only compatible with the vendor’s equipment and limit the desired functionality. A proprietary protocol BMS ties a building owner to a particular vendor for the life of the devices installed, making the vendor the single point of contact for service, support, and upgrades. A proprietary protocol further limits the scope of scalability of the building system with evolving requirements

Building Management System Open Protocols - Types

There are multiple open communication standards, but we are going to highlight the three most popular BMS protocols – BACnet, Modbus, and MQTT.

BACnet

 

BACnet (Building Automation and Control Network)

As described by www.bacnet.org, “BACnet was developed by a committee formed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The committee's main objective was to create a protocol that would allow building systems from different manufacturers to interoperate, that is to work together in a harmonious way.”

The concept of BACnet was originally developed in 1987, which later became an ANSI standard in 1995, and then an ISO standard in 2003. BACnet was created as a standard so any manufacturer that claims their devices can communicate “BACnet,” they must abide to the standard and are independently tested by BTL (BACnet Testing Laboratory).

Modbus

 

Modbus

Modbus.org describes this protocol as, "“Modbus Protocol is a messaging structure developed by Modicon in 1979. It is used to establish client-server communication between intelligent devices. It is a de facto standard, truly open, and the most widely used network protocol in the industrial manufacturing environment.”

Modicon, now Schneider Electric, introduced the Modbus protocol in 1979. Seeing the importance of the Modbus protocol in the market, Schneider assisted in the development of an independent developer and user community to drive the adoption of the Modbus Protocol: The Modbus Organization.

MQTT

 

MQTT (MQ Telemetry Transport)

According to its own website, “MQTT is an OASIS standard messaging protocol for the Internet of Things (IoT). It is designed as an extremely lightweight publish/subscribe messaging transport that is ideal for connecting remote devices with a small code footprint and minimal network bandwidth.”

MQTT was invented in 1999. ISO has since ratified v3.1.1. As devices become smarter at the “edge”, we need more efficient communication protocols so those smaller, smarter devices can deal with data transfer better.

 

Open communication protocols are independent of any hardware or software. The communication rules are publicly available and are suitable for a wide range of BMS applications. Open protocols allow for easy integration of devices from multiple manufacturers into building management systems. Most open protocols abide by a standard that some organizations or industry groups set, like ASHRAE. When manufacturers abide by the “open” protocol standards, it allows for interoperability of system components like sensors, controllers, and actuators.

Open communication protocols are more common now than ever and should continue to gain more market share with market education, and adoption by manufacturers.

Building Management System – Open Protocol vs Open System

Implementing a design based on Open Protocols is a great first step to keeping a site/customer from being “locked” into one manufacturer or service provider, but an open protocol BMS developed with a proprietary programming tool cannot be termed an open system. A truly open and standard-based building management system should have the ability to be programmed and/or operated without any support from the vendor or manufacturer.

It’s More Important Than Just a Protocol

Deploying an open building management system requires more than just an open and standardized communication protocol.

You need:

  1. Open Communication Protocol
  2. Ability to modify and/or make programming changes
    1. This includes access to the software programming toolset so the customer can make the necessary changes, or the software toolset is at least widely available.
    2. This includes access to multiple service providers and vendors, so the customer does not have to worry about territory restrictions
  3. Open-Source Ontology
    1. Initiatives like Buildings IOT’s OAP (Ontology Alignment Project), assist in creating a “common” tagging structure for building data standards. This allows other existing taxonomies to be all combined into one ecosystem and work together to create a semantic modeling and tagging nomenclature.

Open protocols are the foundation of a smart building implementation and bring ease of “getting” the data, but it’s much more than just how something communicates. There are many complex aspects of smart building implementations, and companies like Buildings IOT are here to help.


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