What are Communication Protocols? …and the TOP 3

Communication Protocols for Energy Management SystemsIf you are new to controls or maybe have only worked with one type or brand of controls systems you might be wondering what exactly is a communication protocol and what are the ones available. Communication protocols are sometimes not used in the correct context and even the term ‘protocol’ is sometimes not fully understood when it comes to Building Automation Systems.

communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications. A protocol may have a formal description.

A protocol definition defines the syntax, semantics, and synchronization of communication; the specified behavior is typically independent of how it is to be implemented. A protocol can therefore be implemented as hardware or software or both.

Communications protocol – From Wikipedia, the free encyclopedia

In essence a communication protocol is the ‘formatting’ of how you talk. This can best be explained by relating it to the various languages we speak such as English, Spanish or French. Each language or protocol exchanges the same information such as temperatures, pressures and control signals, but formats it in its own way and therefore can only be used by devices or software that speak the same language or protocol.

Each protocol can then be looked at in more detail to see what media can they talk on and what various ways can that information be routed. Meaning we have defined that they speak English or Spanish, but do they talk on the telephone? in person? using tin cans and string? and if they can’t speak directly to the other person do they have a way of routing the information by use of other means? Kinda like using the postal mail, email or carrier pigeon.

BUT let’s get back to the protocols and I’ll worry about typing up another article about the various ways protocols actually get their information to where it is needed later.

There are 3 prominent communications protocols that stand out in the Building Automation Systems industry. Those are:



BACnet became an ASHRAE/ANSI Standard (135) in 1995 and the following years showed several DDC Controls manufacturers, such as Alerton, Automated Logic and Delta Controls with dedicated BACnet product lines. BACnet can be said to be the youngest of the group and also the only of the three that was not developed or spear headed by a ‘for proft’ corporation or organization.

BACnet is almost always associated with Buildign Automation Systems and HVAC Controls. It’s primary focus was to be used with devices and systems whose applications included heating, ventilating, and air-conditioning control, lighting control, access control, and fire detection.


LonWorks was a creation of Echelon Corporation in 1988 and was added as an ANSI standard (ANSI/CEA-709.1-B) in 1999. LonWorks is not the oldest of the three, but it is by far more robust and capable than the older Modbus protocol.

Lonworks undoubtedly has a larger number of installed devices with over 90 Million by 2010, however the applications and types of devices that use LonWorks are quite diverse such as embedded machine control, municipal and highway/tunnel/street lighting, heating and air conditioning systems, intelligent electricity metering, subway train control, stadium lighting and speaker control, security systems, fire detection and suppression, and newborn location monitoring and alarming.


Modbus was developed in 1979 by a company which manufactured PLCs, Modicon. Modbus is the grand-daddy of the controls communication protocols. Even to this day new products are being manufactured that still can be used with the Modbus protocol.

The actual base parameters of Modbus have not changed at all over the years, however it has such a large install base and an ‘everybody uses it’ stigma attached to it that it still remains a strong standard.


There are many other communications protocols available out there but the above three are what you are going to come across often while in the field. When I look at the above three I actually see three separate niches that each of them fit well into. Though LON and BACnet have been the Ford and Chevy of HVAC controls for many years and will probably continue to fight for market share in the building automation systems market.

What communications protocols have you used and how do you feel that protocol will be used in the future with Building Automation Systems?

7 Responses to What are Communication Protocols? …and the TOP 3

  1. Scott February 8, 2012 at 20:18

    Good info. I like it. I’m not a fan of Modbus. It’s cumbersome to set up and you have to “call up” a known point to establish comms. Then each point must be renamed to something that makes sense to the customer.
    I like BACnet the best of the bunch because it broadcasts the “who-am I” messages and the many points and devices can be “discovered.” But, that doesn’t make it easy; none of the protocols are easy and take lots of learning to get comfortable with.
    LON can be a pain working with the Snivets. The bottom line to any protocol is a healthy data bus installed properly. Though, there’s always comm issues at the start of a project and found during start-up. I know, I’m hexed with all of them.
    I have much experience with BACnet, LON and JCI N2. I’ll take new construction with BACnet any day. Take care.

    • The Controls Freak February 11, 2012 at 15:19

      Good insights there… I am glad to hear someone NOT say that MODBUS is easy to work with. LOL

      Normally, anyone who has worked with it says it is easy. The truth is that now-a-days MODBUS isn’t used as a sole protocol, so there aren’t controls contractors running around doing MODBUS day in and day out. Therefore, MODBUS ends up being something that other controls contractors have to integrate into their systems.

      That is when the MODBUS nightmare begins… trying to translate old school bits and bytes using strange names for different types of numbers that most DDC controls don’t use today, like integer, floating32, long, word. Just confusing stuff to the layman.

  2. Chris Norris February 21, 2012 at 18:14

    Thanks for the article! I’m a tech who just got into commercial HVAC, and I’m trying to learn the ropes about this all this “controls stuff”.
    Thanks for making a “plain English” resource for us.

  3. The Controls Freak February 22, 2012 at 18:47

    Chris glad you are out there searching for more information on your own. It’s a great quality to have as a controls tech.

  4. Marc Chiz September 5, 2013 at 18:04

    All good reading for me guys. Im a on site maintenance engineer with a Trend963 system installed. Im looking to get to know a bit more and maybe take up the ‘profession’ myself……any ideas where to get a beginner’s guide??…..I have some very helpfull BMS engineers who attend my site to carry out some PPM’s…….and I literally mean some…..buildings only 4 years old. Any help, guidance fully appreciated. :-) :-):-):-):-)

    • Abel B Ramirez II September 5, 2013 at 23:07

      What’s a PPM? Preventative Maintenance? Point to Point…something?

      Trend Controls… nice. I have not had the pleasure of messing with them myself, but it looks like a solid BACnet product. I know they are big in Europe.

      As for a beginner’s guide… specific to Trend or controls in general?

  5. Pingback: 101 Ways to ROCK! as a Building Automation and Controls Technician | The Controls Freak – Controls and Automation Community

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