4  FM quick reads on wireless

1. Wireless Options For Building Automation

Today's briefing comes from Josh Thompson, principal consultant with Point Source, LLC. All building management systems (BMS) communicate by using a language that is understood by every device connected to the system. Unfortunately, these languages, or "protocols" vary from system to system, and not all languages conform to a uniform standard of communications. Some systems have specifications that are accepted by standards organizations, such as the ISO/ESA; others do not. Each system has its own set of advantages and disadvantages, but it is important to note that not every BMS protocol will communicate over every wireless technology. Thankfully, there have been significant advances in translation, and for a relatively small investment, most BMS languages can be converted into a standard that can be communicated wirelessly, one way or another.

With that in mind, there are a wide variety of ways to transmit data between devices without wires. The simplest and most common is infrared. From motion and occupancy detectors that use our body's temperature to trigger an event, or the TV remotes we use to change channels, IR is an important wireless control tool. IR is secure — it can't penetrate walls; it can be passive (like a motion detector) or active (as a remote control), but its communications are typically "simplex," which means it can either send or receive information in one direction. Clearly, in a BMS system, it is as important to know the status of a device as it is to control the device, so "duplex," or bi-directional wireless communication systems have come into favor.

One recent solutions is EnOcean. Focusing on energy harvesting, EnOcean devices use the energy in the environment to operate. A light sensor uses light energy, flow and movement sensors use kinetic energy, etc. They transmit at a reasonable data rate of 120Kbps in a mesh/grid network. More importantly, they communicate in a relatively low frequency range, which allows for transmission distances of up to 300 meters and separates them from other nearby devices.

Another wireless control protocol is Zigbee. It has vast market acceptance in the commercial building control systems community, which keeps development costs lower and, thus, offers a lower cost of deployment. Zigbee is a standards-based protocol (IEEE 802.15.4), with reasonably fast data rates of 250Kbps across a self-forming meshed network. Manufacturer and user support resources for Zigbee systems are readily available. When professionally integrated, most BMS, administrative reporting and even audiovisual controls can be managed with little or no translation.

Finally, the wireless technology that is by far the most widely deployed is WiFi (802.11 a/b/g/n). Used extensively in information technology (IT) systems to network computers and other smart devices, WiFi operates in the ISM frequency bands and is capable of data rates of 20Mbps (rev. a), 54Mbps (revs. b/g) and 300Mbps (rev. n). This is more than enough bandwidth to support hundreds of BMS devices, including networked video, audio and other AV sources across the network, and is very easily managed and maintained by most IT personnel. Such performance comes at a cost, however; although very capable, WiFi devices have relatively high power consumption when compared with other systems.

Wireless Considerations For Building Automation: Interference

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.

Facility Managers Have Multiple Reasons To Consider Wireless Building Automation Systems (BAS)

Today's tip from Building Operating Management comes from Gislene D. Weig of PlanNet Consulting: Facility managers have multiple reasons to select wireless building automation systems.

Wireless building automation system networks, simplistically speaking, are networks of electronic devices designed to monitor and control the mechanical, electrical, and lighting systems in a building. In a BAS network there are mainly three tiers or levels. Tier 1 (the top level — the primary bus) is where devices such as logic controllers, work station terminals, web-servers, and other supervisory devices are networked. Tier 2 (the secondary bus) connects to major mechanical, electrical, and plumbing components like the central plant controller, air volume box controller (VAV), boiler controller, and lighting controller. The third tier is where end devices like thermostats, lighting sensors and others sensors are located. The most common implementation for wireless BAS has been the sensor level (tier 3) due to the ease of installation, flexibility, and lower installed cost.

Wireless systems or hybrid (combination of wired and wireless) systems are worth considering under a variety of circumstances. Here are four cases where it is worthwhile for facility managers to consider a wireless or hybrid BAS:

  • When there is a desire or requirement to implement BAS networks in new, existing or retrofit buildings where wiring is a challenge.
  • If adding more sensors and actuators throughout a building can further improve the comfort of occupants while reducing energy consumption.
  • When wiring is either aesthetically undesirable or cost prohibitive (e.g., historical buildings).
  • When there is a need to increase flexibility. Without a need to re-wire, tasks like re-locating or adding thermostats and sensors throughout a space becomes extremely easy, with a minimum of disruption to tenants.

This has been a Building Operating Management Tip of the Day.

Controls Offer Further Lighting Efficiency

Today's tip is to look at lighting controls for further energy savings after switching to more efficient light sources. Once efficient fixtures and lamps have been chosen, there are really only two ways to further reduce energy use: Reduce burn hours or reduce light output. To perform either of those functions, you need a lighting control.

Commercialization of several novel technologies has expanded ways to apply controls to both existing and new installations. Competition and standardization in wireless communications protocols, for example, now provide options that avoid the usually costly installation of separate control wiring, often a deal-killer when adding controls to existing lighting.

Wireless switching can use power generated by one's finger (when pushing the on-off button) to send a radio signal from the switch to a relay built into (or added to) fixtures in the same room.

Wireless stations, when directed by a control panel, send signals to receivers that control whole circuits of fixtures, or to groups of fixtures based on electronic addresses built into their ballasts.

Reliable power-line carrier control products, using panels and dimming ballasts (either step or continuous), have expanded and become cheaper, offering a third way to retrofit without requiring additional wiring.

These options are competing with the now-standard Digital Addressable Lighting Interface systems that use dedicated low-voltage wiring to control individual fixtures. DALI is often installed in new or heavily renovated facilities while ceilings are open and spaces are unoccupied. Wireless systems are often applied where spaces are already in use.


wireless , building automation systems

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