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Every profession has their own secret language, and the world of building automation is no different.

In this post, I will help you to demystify the lingo of building automation by exposing the 5 most common terms in the building automation world.


How many ways can you call the exact same thing something different. Now the true diehards, who simply live to focus on the minutia are probably going to hate what I’m about to say.

Let’s get real folks, BMS, EMS, BAS….

They’re all the same thing….

Now before you start flaming me and dropping off the site like flies let me explain. Building management system (BMS), energy management system (EMS), building automation system (BAS), here’s the dirty little secret they basically do the same thing.

Sure there’s minute differences here and there, but really, for all intents and purposes there the same thing. They all basically control building systems specifically systems related to HVAC and energy control to provide an optimal environment for whatever the folks are wanting to do in the building.

BAS Term #2 Balancing

Balancing, nope we’re not talking about the Olympics. And were definitely not talking about me putting on a leotard and trying to do dismounts.

And for those of you who just gouged your eyes out at that mental picture, sorry for the imagery.

Balancing is where you make sure the airflow and water flow that heat and cool the building are being accurately measured and properly supplied, to the right parts of the building.

By the way, this balancing act, it’s done by someone called the balancer.

BAS Term #3 Commissioning

You know as a Navy veteran, there really is only one way this word should be used in the building automation industry stole it from us but that’s okay. So were going to talk about the “other” definition of commissioning.

Commissioning is where a person, often called the commissioning agent, will verify that the building automation system is controlling systems according to the sequence of operations.

And for you folks who don’t know the sequence of operations, that’s a fancy way of saying house stuff supposed to work.

BAS Term #4 Tuning

I bet you didn’t know, that those of us in the building automation space, are prolific guitar and piano players. Yep that’s right, because were always tuning.

I’m here all night be sure to tip your waiter.

Seriously though, tuning is where the building automation professional, adjusts the settings that control the outputs of a building automation controller. Over time, these, control loops, will begin to get out of tune.

Now if you’ve ever heard in musical instrument that’s out of tune it’s just not performing right. Well building automation systems, specifically controllers, can do the exact same thing. That’s why it’s regularly recommended that you tune your controllers once a year.

BAS Term #5 Trunk

Is not much of a surprise, that building automation controllers need a way to communicate with one another. What can be surprising for some, especially those from outside the building automation industry, is the term we use to describe the communication network that controllers use.

Trunks are simply another name for field buses, which surprisingly is an even more confusing and less descriptive name. It’s almost as if, we want you to go buy a bunch of crackerjack boxes and find your secret decoder ring.

But, that’s why you come here and read my articles, as you can tell by my profile pictures I’ve eaten one too many cracker jacks….

Seriously though, trunk, field bus, they’re all the same thing. They are the network that controllers utilized to communicate to and from one another.


There you have it folks, short sweet and to the point. Hopefully this cleared up a little bit of confusion around common building automation system terms.

So, what terms do you think I should add? What is a commonly misunderstood term that you think would be important for someone in the building automation space to understand?

Let me know in the comments below.



Phil Zito

Written by Phil Zito

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