May 2011

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Wireless In HVAC Controls
We’ve come a long way, baby !

Steven R Calabrese

Steven R. Calabrese
Control Engineering Corp.

Contributing Editor

Does anyone remember life before cell phones? Okay, we had that stretch of time when many of us had wireless pagers. A lot of good they were, huh? So you’re out and about, driving from one appointment to another, and your pager goes off, displaying a phone number for you to call. I remember once receiving a page in the pouring rain, having to find a pay phone, and braving the elements only to find out that my boss wanted me to bring him back a sandwich! Well, that’s not exactly how the story went, but close enough for the purposes of this article. The fact is, we have come along way in just a few short years, in terms of wireless technology. Anyone using a cell phone or connecting wirelessly to the Internet can testify to this, and it holds true in our business as well. Whereas seemingly just a couple of years ago we were “held to the hardwire”, in terms of electrical controls installations and remodels, nowadays we have wireless at our disposal. In this installment we explore just a few of the products and applications that are available to us today, that are “changing our lives” in terms of the way we go about our business.

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I remember my first exposure to industry-specific wireless technology. The project was an interior remodel of a medical office building. The airside HVAC systems consisted of large multizone air handling units, with the zone dampers local to the air handling units and the zone sensors hardwired back to the zone dampers. The remodel consisted of a complete gutting of the spaces, and a rebuild/rezoning. As such, the existing sensor locations were demolished, and new sensor locations were published on the proposed floor plans. Installing new sensor cabling was deemed “cost prohibitive”, and so the wireless option was proposed.

The new control system installed was a “first-run” wireless system, consisting of wireless receivers that were installed in the ceiling spaces, and these rather “clunky” wireless zone sensors that, to my recollection, utilized 9-volt batteries! Once completed, the system worked just fine, save for a few bugs that needed to be worked out with regard to (poor) reception for a couple of the zones. I think we ended up having to add another receiver in the ceiling, but aside from that, it worked like a charm, and for the technology at the time, it was a real “breakthrough” in terms of the way we approached such challenging applications. I will say that, I do remember that the sensors were attached to the walls with Velcro, making them more or less portable. This launched a whole new variation of the old concept of “thermostat wars”!

Fast forward to present day, and I find myself walking through an old warehouse building with vintage multizone air handlers and pneumatic controls. The proposal at hand is to replace the pneumatic controls with digital controls, for the air handlers themselves and for all of the zones. In this application, the sensor locations don’t change, however there are no wires to re-use, just pneumatic tubing. And no budget to allow for installing new cable (and conduit!). So the wireless option is in consideration. Of course at this point in time the sensors are more “standard” size, and they utilize what I’ll refer to as a “watch battery”. And the receiver is streamlined and purportedly more reliable than anything from the past. All in all a good application…stay tuned, and if the client goes for it, I’ll write about its success in a future column (or about the pitfalls encountered on the way to its success!).

[an error occurred while processing this directive] Another application that has gained widespread popularity is wireless carbon monoxide (CO) sensing, most notably in parking garages. Whereas once upon a time a whole bunch of cable and conduit had to be installed in order to provide the requisite sensing/ventilating system for any enclosed parking garage, these days we have wireless technology at our disposal. As I’ll be dedicating an entire column to the topic of gas detection somewhere down the road, I’ll leave the nuts and bolts of that discussion for then. I do, however want to touch on just a couple of the concepts that make this a viable alternative to the hardwired method. One is battery life. In the past, this was an issue. Not to say that it’s gone away, but its much less of an issue due to miniaturized circuit and sensor technology and increased battery life. You still need to routinely replace batteries, just not as often. And as an added benefit, the present-day systems will scan the wireless sensors and report on battery life.

The other thing about these wireless CO detection systems is that many of them use what’s referred to as “wireless mesh network” technology. Simply put, the sensors themselves make up a wireless communication network, communicating from sensor to sensor, ultimately back to the central receiver. If a communication path fails for whatever reason, the system is “smart enough” to find another path.

Lastly, for this column anyway, as I’m sure that there are plenty of other products and applications that I’m not covering herein, I wanted to touch on wireless communication routers. Back in ’09 I attended the AHR Expo, the last time it was in Chicago. Subsequent to the show, I reported in this column on some of the new products that caught my eye, one of which was a wireless BACnet communication device. The concept is simple. You install a transceiver at either end of what you would consider a non-bridgeable segment of required communication path, which would be, for instance, between two buildings. I’m curious to know how well this works, and I hope to find out first-hand, seeing as I’m presently looking at this very application as it applies to two separate buildings on the same piece of property. If my proposal is accepted, the property will become the proving ground for my first wireless BACnet application!

Tip of the Month: When it comes to wireless, we need to be careful up front, in order to make sure that what we propose to install will end up working the way it’s intended. We’ve all lost cellular service in the middle of a call, whether it be due to a driving through a dropout zone, through a tunnel, or whatever. The point is, there’s never a guarantee that there will be a clear and continuous path to wireless communication. Sure, the technology has improved over the years, but do yourself a favor and heed the manufacturer’s guidelines for system design and initial site survey, to determine whether or not the wireless product will even work in your application. At best, you may need to provide additional wireless repeaters. And at worst, you may end up having to hardwire the whole darn thing after all!


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