Hard-wired building automation systems (BAS) have long been used to optimize the performance of mechanical systems in commercial and industrial facilities. As the backbone of many buildings, these systems are known for being reliable and secure; however, they can be somewhat inflexible, due to the fact that a hard-wired BAS often requires running wire and conduit over long distances, which can be difficult - and sometimes cost-prohibitive - in retrofit situations.
Enter the wireless BAS, which experts say can be installed easily and cost-effectively during new construction or even after a building is completed. Another benefit is that wireless technology allows the BAS to be expanded should building occupants change their requirements - or their physical spaces - in the future. As for reliability and security, controls manufacturers are quick to point out that wireless technology has matured to the point where a wireless BAS can be as reliable and secure as a wired system.
CUTTING THE CORDFirst cost is one of the primary concerns of building owners and operators, which is why many are intrigued by the lower upfront cost of wireless BAS. According to Patrick Harder, product manager for Johnson Controls (Milwaukee), the wiring installation - including materials and labor - typically constitutes 46 percent of a BAS project cost. Without the high costs of wiring, most wireless BAS projects become less expensive than their wired counterparts.
A wireless BAS also offers increased application flexibility, whether at the network automation, field controller, or room sensing levels, said Harder. “Sensors and devices can be freely placed where needed, keeping in mind that the optimal placement of sensors can also result in better control. In an occupied building, disruption to the tenants is minimized when building controls can be adjusted through simple wireless control placements.”
Minimizing disruption is one of the greatest benefits of wireless BAS, said Davis Watkins, vice president of commercial sales for Advanced Telemetry LLC (San Diego). “Our wireless network is deployed within the building through a central station touch panel, and then the existing controls (thermostats) for the HVAC systems are replaced with thermostats with embedded wireless transmitters and then joined to the network. Through the touch panel, the entire system is taken to a website that allows central control, schedule setting, and monitoring capabilities.”
Achieving sophisticated control schemes in new or existing spaces is also easier with wireless BAS, and installation and retrofits are faster and simpler, said Jay Hendrix, business line manager for Siemens Industry Inc.’s Building Technologies division (Buffalo Grove, Ill). “Upgrades and expansions to legacy systems can be accomplished seamlessly and cost-effectively, and owners have more flexibility to plan and stage migrations to accommodate budgets and schedules.”
With wireless technology, buildings become more marketable and owners are better prepared to capitalize on future technologies, said Hendrix. “It’s a fact that wireless environments allow building owners and facility engineers the ability to easily adapt to changing needs, while helping them eliminate costs and other constraints associated with re-wiring and maintenance every time a tenant reconfigures a space.”
Additionally, noted Harder, a wireless infrastructure will help the BAS access data from multiple enterprise applications and assimilate this data into meaningful information that helps busy managers operate more efficiently, including remote monitoring and control capabilities.
SCOUTING THE SITEWireless BAS are suitable for just about any application, although small buildings are leading contenders for this technology, said Watkins. “Typically, these systems are deployed as a retrofit to allow small business owners to take control of their energy consumption and help enhance the bottom line. Retail, restaurants, convenience stores, and office buildings are just a few of the applications that can take advantage of this type of product.”
Niche building applications where hardwiring is challenging or physically impossible are also prime candidates for wireless BAS, added Harder. Some of these applications could include historic buildings or structures in which decorative surfaces abound, such as marble, granite, or glass. Other applications that could benefit from wireless technology are structures with excessive brick or concrete walls, and buildings with frequent tenant turnover or changes in use.
In order to determine whether or not an application can benefit from a wireless BAS, a pre-site survey should first be completed. The survey is a basic checklist that will detail such factors as number of thermostats, network location and distance from touch panel, type of electrical service and main service amperage, and overall distance between wireless devices and touch panel, noted Watkins.
A walk-through of the retrofit site with site survey tools is also beneficial, Harder explained, and contractors should utilize mechanical drawings and information about tenant usage, as well as consider the life cycle changes in the building to avoid repetition. “It is also important to consider the communication distances between the wireless devices. Most wireless systems have built-in signal strength indication, which is useful for site surveys before installation, as well as during and after.”
In addition, consideration should be given to building materials, as wireless signals do not travel well through metal, which can be a problem in older buildings that are constructed with plaster lattice containing wire mesh. The good news, said Harder, is that most commercial buildings are constructed of materials well suited for wireless communications.
“Even though there are always metal obstructions, there are rules of thumb to follow that allow wireless communications to operate reliably in this environment,” said Harder. “One thing to keep in mind is that wireless does not always equate to ‘no power required.’ Wireless-enabled building automation controllers and wireless repeaters require some form of ac power in order to operate. There will be electrical costs associated with the installation of wireless repeaters in a wireless BAS.”
Another obstacle can involve the equipment in some buildings, which may be located in reach of the occupants (e.g., unit ventilators in schools), causing challenges for antenna placement, said Hendrix. “It’s important to think through these issues and create a layout drawing using the floor plan and mechanical layout drawings as a basis. Identify coverage areas of each wireless controller and check for good coverage and a strong mesh. Identify areas where there are gaps or holes in the mesh where repeaters will need to be added.”
SAFE AND SECUREBuilding owners and operators may have some reservations about the reliability and security of wireless BAS, but Hendrix pointed out that wireless BAS systems can employ all the latest security measures as wired networks. “Some might say that wireless mesh networks may be more reliable than wired networks because of their self-healing nature. If you cut a wired network, there is no chance of communication beyond the cut point.” That is not the case in a wireless system.
Harder added that, thanks to industry standards, the wireless offerings in the marketplace are becoming more robust than ever. As for interference from neighboring wireless systems, “Our wireless infrastructure solution ensures signal strength in a managed environment that minimizes interference and maximizes reliability. Most wireless networks are designed to coexist with other wireless networks in a commercial building and transmit at very low power levels to limit any interference within the same air space.”
That being said, building system security should not be compromised in order to use wireless technologies, said Harder. “Networks must be identified as trusted networks before connecting to the system and standard protocols are encrypted. The technology leverages the security features in ZigBee, BACnet, and IP standards.”
There is a possibility for interference from devices that use radio frequencies, so to minimize the chance of interference, a proper channel management plan should be utilized, noted Hendrix. “Siemens research revealed that the most effective way to eliminate possible interference between wireless HVAC devices and wireless LANs (WiFi/802.11) is to use frequency channels in the 2.4 GHz frequency band that wireless LANs don’t typically operate on (IEEE 802.15.4 channels 15 and 20), or better yet, were in the part of the band never used by wireless LANs (IEEE 802.15.4 channels 25 and 26). Research and field experience have shown that if you must use the same frequency, simply putting a little physical distance between wireless LAN devices and wireless HVAC devices that use the same frequency will minimize the chance of interference.”
While wireless technology has been available for many years, it is relatively new to the commercial building automation market. The technology is beneficial for contractors because it gives them the ability to offer viable - and profitable - solutions for applications in which a wired BAS may not be feasible. As Watkins noted, “By helping customers take control of their buildings’ energy consumption through the use of a wireless BAS, contractors can begin moving toward a more proactive business partnership with their customers.”
Publication date: 08/23/2010