Wireless Considerations For Building Automation: Interference
July 8, 2014
Today's briefing comes from Josh Thompson, principal consultant with Point Source, LLC. Whenever a building management system (BMS) is considered, the topic of wireless options is bound to enter the discussion. With a wireless solution, obviously, there are no wires to run, no conduit to buy, and no holes to drill.
When considering the construction costs of a hard-wired solution, the argument in favor of wireless system integration is both compelling and often valid. That said, all things come at a cost; before making any decision, it is always best to be well informed.
One significant factor for consideration is that of wireless radio frequency (RF) interference between nearby systems. Note that most of the technologies in use today operate in the Industrial, Scientific and Medical (ISM) frequencies. This spectrum, which spans from roughly 900MHz through 2.5GHz, falls within what is known as the "wireless sweet spot;" so called because these frequencies offer the best compromise between the signal's capacity to transmit data (bandwidth) and the distance these signals can be transmitted.
Because of this balance, however, literally millions of devices operate within this spectrum. This may cause problems, which are further complicated by the fact that the ISM frequencies are unregulated, meaning that there is no guarantee that the device deployed as part of a BMS will not be interfered with by another device, such as a cordless telephone, door openers, car alarms, a neighbor's WiFi system or even a nearby microwave oven. This factor alone brings the decision to deploy any wireless technology into a facility into question, and all but absolutely excludes its use in a life-safety system.
Clearly, there is no right or wrong answer when considering the deployment of a wireless technology as part of a building management system. The decision should be based on a careful weighing of the risks vs. the rewards of such an integration. If, for example, a facility stands to save a significant amount of money in energy costs, with nothing to lose by an occasional loss of communications with a device, then the answer is clear. If, however, a flow meter or sensor is to be monitored, the loss of which would compromise a critical building system, perhaps a wired solution is the best option at any cost.
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