May 2011 |
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Wireless In HVAC Controls
We’ve come a long way, baby ! |
Steven R. Calabrese |
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!).
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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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