Wireless Thermostat Study

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Wireless Stat Study (Completed 11/18/2011)


  • Found very recent article on the state of wireless BAS. Important points to consider in our application of wireless space sensors are found below, taken directly from the article.

Commercial wireless BAS: Consulting-Specifying Engineer State of the wireless BAS industry

  • Trends
    • For an overview of how wireless technology is being applied, see the ZigBee Alliance and EnOcean Alliance examples.
    • Of the wireless technologies currently available, RF technology is the most promising, as it has the highest level of interest, participation, development, and implementation with regard to the commercial building automation market.
    • The mass market driver and business model for most wireless devices is currently more attractive to the high-volume residential market.
    • The challenge is that the technologies being developed for the commercial building automation market must be significantly more robust than the technologies that historically have been applied in the residential market. Commercial wireless systems must overcome barriers such as application development, integration, support, interoperability, security requirements, interference from noise and obstructions, and codes and FCC regulations.
    • Fortunately, wireless industry organizations are developing standards and technologies to satisfy both the low-cost, high-volume residential and more robust commercial markets.
  • Where is the market today?
    • Before designing wireless devices into a control system, the products and systems must be thoroughly evaluated to determine how they will perform in the desired applications.
    • Several key factors must be considered:
      • Application
      • Functionality
      • Products
      • Radio frequency (Hz)
      • Signal strength and distance
      • Security
      • Network architecture
      • Protocol
      • Interoperability
      • Interchangeability
      • Lifecycle cost
      • Support
    • Wireless devices for commercial BAS vary in their approach to all of these factors. As a result, the wireless commercial BAS market is proprietary.
    • The devices and systems offer initial design and implementation flexibility but have significant lifecycle limitations.
    • Since the systems are not interchangeable, the operation, maintenance, upgrade, and expansion of a wireless commercial BAS sensing system is typically limited to a sole source provider after the initial installation.
    • Developing a wireless project with only performance specifications and vague requirements will most likely result in disappointment.
    • Wireless technology is in its infancy relative to the commercial controls market.
    • Extra attention must be paid to understand how these continually evolving products can be effectively integrated into a commercial BAS.
    • The impact of each of the key factors listed above must be understood before design and specification can begin.
  • Application: The desired application must be considered from both functionality and product perspectives.
  • Functionality: What purpose will the wireless device perform?
    • What other systems do the wireless devices need to share information with, and what kind of information will be shared?
    • Products: Are products available to address the functionality?
    • Keeping track of the functionality of a growing list of wireless products is a daunting but necessary task
    • Radio frequency (Hz): IEEE 802.15.4 identifies 2.4 GHz as a global frequency with regional frequencies of 915 MHz (Americas) and 868 MHz (Europe)
    • A popular standard utilizes a 2.4 GHz signal, and manufacturers offer a number of products that are built on that frequency
    • Do not assume that a frequency can be used in a facility just because it is licensed nationally.
    • Signal strength and distance are closely related. The stronger the signal, the farther it will travel. However, the stronger the signal, the more power it consumes and the more likely it is to interfere with other devices and systems.
    • The effective distance will be further reduced by obstructions.
    • The distance estimates are critical to the design because they will determine the location and quantity of the devices.
    • It is important to remember that the quality and reliability of RF communication can be significantly impacted by the surrounding environment, as can any signal that is transmitted in an open media and exposed to unknown sources of interference.
    • Most manufacturers provide test transmitters and receivers to test signal strength and quality throughout a facility. Since wireless devices for commercial BAS are primarily installed in existing facilities, the signal strength can be physically tested. A signal test prior to system design will provide valuable data to optimize the design. Repeaters can be added to boost signal strength if required.
    • Testing the signal strength before device installation should be a specification requirement, witnessed by the design engineer, to verify the submitted solution will work properly. If the signal is weak, repeaters can be added as required to boost the signal.
    • Do not assume a client will allow the use of wireless devices.
  • Security: Consider proprietary network vs. Web.
  • Network architecture: Wireless network architectures have two primary structures: mesh and hub.
    • Mesh networks are more popular.
      • All devices in the network are peers. In a mesh network every device is both a receiver and a transmitter. Each device acts as a repeater, relaying messages from one device to another. Mesh networks automatically and dynamically configure themselves to “speak” with neighboring devices that have the strongest signal. This creates a self-healing network. If a device drops out and stops communicating, the remaining devices will search for other device signals and automatically reroute traffic.
    • Hub networks use a centralized intelligent “hub” device to communicate to a number of individual lower-level “spoke” devices.
      • The hubs then communicate to each other over wired or wireless media.
      • Potential cost advantage
      • The hub architecture has the disadvantage of being susceptible to single points of failure.
      • If a hub goes down, communication to all spokes is lost.
  • Protocol: The protocol used by each device and the rules for message communication are important to understand.
    • All devices in a wireless system must use the same protocol and transmission rules; otherwise, gateways must be provided to provide protocol translation.
  • Interoperability: Interoperability is defined as the capability of one system or device to speak with a system or device from another manufacturer, be it wired or wireless.
    • BACnet, LonWorks, and Modbus
    • Most wireless networks do not speak BACnet, LonWorks, or Modbus as the wireless protocol but offer gateways to convert the wireless protocol to BACnet, LonWorks, and/or Modbus
    • Gateways should only be used when absolutely necessary, as they complicate the design, maintenance, and support of the systems, and create single points of failure.
  • Interchangeability: Interchangeability is the ability to integrate devices from two or more manufacturers into the same network, including the flexibility to replace a device from one manufacturer with a functionally identical device from another manufacturer.
  • Lifecycle cost: The lifecycle cost for wireless sensing systems with commercial BAS is comprised of many facets including initial installation, maintenance, upgrade, and expansion. Wireless sensing systems for commercial BAS are single vendor solutions.
    • The strength and longevity of the manufacturer/vendor should be a key evaluation factor when selecting a solution. The specifications should require the use of current production, off-the-shelf products that have been installed in three to five similar applications with a 2- to 4-year production history. Do not risk system reliability and sustainability by allowing the use of obsolete or first-run products.
    • Quality products, manufacturers, designers, and integrators are necessary to support the system from concept development and design through implementation and operation.
  • Support: Strength of company response and individuals in area providing service.
  • Wireless industry organizations
    • The wireless industry organizations that are leading the way to developing wireless technology for commercial BAS applications are ZigBee, Z-Wave, and EnOcean.
    • The companies listed on these websites provide a good place to start a wireless application investigation, but they do not represent all providers of equipment that use these wireless standards.
    • Investigation of the current products available on the market reveals a heavy slant toward the residential market.
    • The products available for the commercial market are slim.
    • The issue is that commercial wireless technology and products are relatively new, and the commercial BAS market does not adopt new technologies overnight. Therefore, a variety of manufacturers are developing devices for the residential market because it is quicker to respond, has lower capital investment for the user, has a certain percentage of early adopters or “techies” that like to experiment with the latest and greatest new products, and represents a large potential mass market. It’s only a matter of time before more of these products migrate into commercial BAS applications.
  • Can wireless devices work in commercial BAS?
    • The short answer is yes. Zigbee, Z-Wave, and EnOcean wireless sensing systems are being integrated into commercial BAS worldwide by a variety of providers, in a variety of applications.
    • The long answer is yes, but lifecycle costs and sustainability play an important role in the decision to go wireless. The designer must understand the benefits and restrictions of wireless technology in order to develop solid business opportunities for commercial facilities.
    • Research not only the features and benefits but also the constraints and limitations.
  • Personal experiences with major controls manufacturers
    • Trane entered market early and may have an advantage from development point of view.
    • JCI also early market entry that caused Trane to "shape up". May have longer history than some.
    • Honeywell has product but no experience with them.
    • Cochrane recommending Spinwave on its own network instead of Eversco on the Internet network.

References


Questions

  • Is repeater needed for application at the Green Garage?

TO DO

  • Plan / Do / Study / Act / Repeat
  • Monitor results of using Spinwave sensors.
  • Add one hard-wired stat to take over if all 4 wireless sensors fail at the same time. DONE