October 2013

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Ten Innovations

That Made Life Easier in the HVAC Controls Biz

Part Two of Two

Steven R Calabrese

Steven R. Calabrese
Control Engineering Corp.

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Last month I listed out five “improvements” to products that we’ve come to depend on in the HVAC control biz. (To read Part 1/2) This month I continue the list, touching on one product and four “concepts” this time around. So here we go…

Electronic temperature controllers

All hail the electronic stand-alone temperature controller! Back in the day, this device reigned supreme. At least in my corner of the business. I worked for a mechanical contractor right out of college, and we had licensed electricians on staff that would install controls for the mechanical systems we put in. I was employed to design and draw up these stand-alone control systems, using the tried and true methods of the day (relays, ladder logic, etc.). The one device I came to rely upon was the self-contained electronic temperature controller. This device was the equivalent of the pneumatic receiver-controller popular a generation (or two) before. It was nothing more than a small box you brought  power to, and attached a remote temperature sensor to. The device was able to control two-position end-devices as well as modulating control devices. I used this thing for everything I could, seeing as I had no access to any line of DDC at the time. It came in different varieties and was made by several different manufacturers, but they all worked in the same manner. Simplicity at its best. No network, no front end. Just a digital display on the cover and some buttons and/or dials to establish setpoint.

Nowadays I’m certainly more inclined to use a digital controller to do most any form of temperature control, even if it ends up being a stand-alone application. But those electronic temperature controllers are still available, and I’m sure they still sell a ton of them. Not all of us are DDC-savvy, and for those mechanical contractors who don’t like to have to rely on a third party to perform their temperature control installations, this is still a viable option. Long live the electronic temperature controller!

Direct Digital Control (DDC)

In order to appreciate where we’re at with this, it’s good to review just how we got here. First there was simple electrical control, whereby a thermostat would make and break an electrical circuit to control some cooling process, maybe a fan. Then there was the heyday of pneumatic control, which allowed for not only two-state control but also proportional control. The development of the transistor ushered in the era of electronic control, whereby we were now able to do everything we once did pneumatically, electronically. Tubes were replaced by wires, and that big old air compressor hit the trash.

And then came DDC. The birth of the computer paved the way for processor-based control as we know it today. However DDC wasn’t created overnight. It has evolved over time, just as with any technology, to where it’s at now. The first versions of digital control systems were what are referred to now as “centralized systems”. These systems consisted of a main central processing unit, to which all inputs and outputs were wired. I remember seeing one or two of these, pre-Y2K, and really haven’t seen any since. I suppose any still in existence at the turn of the century were torn out in apprehension of the “Y2K turnover”.

Nowadays what we have are “distributed systems”. With distributed DDC, the computing power is de-centralized, and not concentrated in one location via a single CPU. The logic is spread or distributed among digital controllers, each equipped with microprocessors, of which are selected and configured to perform the control of a specific piece of equipment or subsystem.

Yeah, we’ve come a long way in a seemingly short time. DDC is maybe not so much still in its “infancy”…more like a toddler in a training diaper! Advances in the technologies are made on almost a daily basis, and interoperability, connectivity, and wireless communications are the buzzwords of the day. Exciting times for sure, only to become more so in the never-ending future of digital communication and control.

The Internet

The Internet wasn’t invented for the HVAC/controls industry. But boy, we sure do benefit from it! How so? Well at first, just being able to log in to a system remotely for troubleshooting was a big benefit, even alongside the (not so?) trusty method of dialing in via modem. Nowadays it’s so much more than that. We have remote scheduling and adjustment of setpoints. We have remote alarming and notification. Accessing a Building Automation System’s (BAS) front end is as easy as surfing the web. The system graphics are now web pages. Yes, the BAS has worked its way into the mainstream. Anyone Internet savvy (and who’s not anymore?) can navigate an HVAC control system. What’s more, with the development of the smartphone and advances in wireless communication (hold that thought), we can now receive alarm notifications on our cell phones, and call up the BAS using an app!

Yes, the Internet has done a lot for our industry. Seems like just yesterday that the only way to access a building’s networked DDC system, was to be on site, in front of a dedicated computer running proprietary software, having specialized knowledge of how to get through menu pages and 2-D graphics. It’s all good, and it’s only going to get better. Trust me on this one.


Way back in 1995, The American Society of Heating, Refrigeration, and Air conditioning Engineers (ASHRAE) completed Standard 135: The BACnet Standard. Basically defining a standard protocol for digital network communication in our industry. You see, back then, all of the major digital controls manufacturers had controllers that spoke their own languages. There was no real opportunity for these controllers to be networked to controllers of other vendors. What this did was to create a scenario whereby if one manufacturer’s product got installed in a given facility, the facility was more or less “locked in” to using that manufacturer on any future expansion of the Building Automation System (BAS). Although the BACnet standard was not entirely created to remedy this scenario, it has nonetheless done so, and in good fashion. Today, most if not all of the major manufacturers abide by the standard, and end-users are demanding open systems as opposed to closed systems with proprietary communications protocols. I’m telling you, some of these folks don’t even really know what they’re asking for, as long as the end result is the same: interoperability. Meaning that, after I sell them a BACnet installation, they don’t have to rely on me and only me in the future, when they add that annex or remodel a whole floor for a new tenant.

The BACnet standard has defined how we now do things with regard to digital communications in the HVAC industry. Not limited to control systems manufacturers, BACnet is now widely available on manufactured HVAC equipment such as chillers and rooftop units, and on supporting equipment such as variable frequency drives. BACnet is here to stay, and I’m here to tell you that it’s been a long time coming!


We live in the Age of Wireless. Cell phones, wireless Internet, TV remote control. Wait, that last one has been around forever, right? The point is, technology has impacted our lifestyles and there’s no turning back. The latest trends in wireless, in the world of HVAC controls, include wireless CO detection systems (parking garages), wireless space temperature sensors, wireless switches, and wireless communication routers. If there’s something that has traditionally relied on wires for functionality, chances are that it can now be done wirelessly. And I don’t mean power wiring, although maybe that’s just a matter of time! Seriously though, the wireless technology has propagated our industry, and however slow some of the concepts and products are to catch on, they no doubt will, as the technology advances and reliability improves. What was once an “iffy” thing to try, for instance, going wireless on a space sensor in the lobby of a downtown hi-rise with marble walls, nowadays it’s very much worth a try. And in most (if not all) attempts, in the end it just works. Time for our industry to join the rest of the world, and embrace the technology. After all, it is, without a doubt, the Wireless Age.

Tip of the Month: A Word About Wireless – even with the current state-of-the-art, you still need to be sure that wireless will work given your application. Don’t worry. The manufacturers are there to help, with products that test transmission/reception conditions, and technical support that will guide you through to the proper solution. Just don’t be afraid to ask for it. Or else you may end up with a very costly installed wireless system that just can’t seem to communicate, no matter what you try to do to make it work. In other words, leave it to the experts (product manufacturers) to determine the best solution for your wireless application.


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