Wireless controls

The advantages, future, and obstacles facing the development of wireless controls are discussed with this month's panel of experts.

05/01/2008


CSE: What are the advantages of wireless controls?

TIM KUHLMAN : As with other systems that use wireless, it allows for more flexibility in making connections in the system. It can lower the cost of construction by not having to route cabling in areas that are inaccessible or where conduit penetrations can be expensive or problematic. There are advantages to avoiding a roof penetration or routing conduit through an ornate building lobby to make a control system connection.

STEVE TOM : The primary advantages of wireless controls are reduced installation costs, particularly in retrofit projects, greater flexibility, and better architectural compatibility in some situations. The reduction in installation costs comes from no need to pull communication wiring to the device. This is especially advantageous for battery-powered wireless sensors, as there is no requirement for power wiring either. It also is an advantage for externally powered wireless controllers, as running wires to the nearest source of power may be easier than pulling communication wiring throughout the building. Greater flexibility stems from easily repositioning controllers and sensors after installation to accommodate building reconfigurations or new construction. The architectural compatibility issue primarily relates to wireless sensors, as they can be mounted on marble, concrete, historic structures, etc., where drilling is not practical and exposed wiring is not acceptable.

KEITH LANE: The advantage of installing wireless technology within a commercial building is the potential reduced cost of installing a conventional wired network. The cost per control point for both lighting and HVAC systems can be reduced when using wireless controls. Building owners, especially those looking for a LEED-certified building, want the most energy efficient and occupant friendly building at the lowest costs. There is sometimes a compromise between the initial cost of control points within an energy management system and the ability to control the HVAC system based on having real time accurate data. Lower-cost wireless controls allow for more effective operation of energy managements systems and as a result a more efficient building. Wireless control integrated into lighting systems also allow the occupant more control of his or her work area.

JIM KOHL : Wireless controls offer users a greater level of location flexibility for better sensing accuracy. Wireless controls also offer reduced installation times, especially in renovation projects, and lower relocation costs.

CSE: What obstacles impede wireless controls?

TOM : The primary obstacles that impede wireless controls are an increased potential for communications failure, potentially increased maintenance costs, and a lack of long-term experience with wireless controls. Conventional wired control systems have excellent reliability. On rare occasions noise from nearby equipment can create communication problems. Once installed, they tend to work flawlessly for decades. When problems do occur, troubleshooting and correcting them can be much more time consuming than with wire led networks.

KOHL : Interoperable standards to enable open wireless technology are not in place today as with conventional wired solutions. There continues to be resistance and conservatism regarding the reliability and security of wireless controls, despite widespread acceptance of the technology in other categories.

KUHLMAN : All RF wireless control systems use a very limited commodity, the radio frequency spectrum. There is limited bandwidth, the bandwidth has to be shared with other devices and wireless devices are susceptible to noise and interference. As the use of wireless devices of all types increase the problems of noise and interference also will increase.

LANE : Engineers will need to successfully integrate the wireless controls into future designs. The systems will need to prove reliability in actual installations over time. These systems also will need to prove that they will not be susceptible to interference from other wireless systems or cellular technologies in close proximity. Additionally, the wireless controls will have to integrate into existing systems that require new additionally sensors. Standards need to be developed in the industry to ensure interoperability between control devices.

CSE: Is lack of interoperability between wireless control devices an issue? What advances have addressed this issue?

LANE : Interoperability between control devices is critical. Two main control technologies have emerged, WiFi (IEEE 802.11) and Bluetooth. WiFi has an effective distance of 500 meters where Bluetooth had an effective distance of approximately 10 meters. Bluetooth and WiFi are the first open source wireless protocols using a star topology. Based on the standard distance between control sensors in the commercial building environment, Bluetooth technology will most likely not play a major role in the future implementation of wireless control systems. Short distance applications, less than 10 meters, required during the commissioning process may be accomplished with short-range Bluetooth technologies. ZigBee is an open source protocol (IEEE 802.15.4) using Frequency Hopping Spread Spectrum technology. ZigBee is relatively new and can support a range of between 30 to 75 meters. Because of its performance attributes and general implementation in everyday computers, IEEE 802.11b WiFi appears to be the favorite of becoming the established wireless protocol in commercial building equipment control sensors and actuators.

KOHL : Interoperable wired solutions like the BACnet, LonTalk, and Modbus protocol standards are available, but no viable wireless solutions are available yet. So this is an issue.

TOM : I have not seen any interoperability problems with wireless controls to date, but that is primarily because the systems are new enough that they have been installed and maintained by a single manufacturer. At the top layer of a controls system, interoperability is usually not a problem because at that level most controllers, workstations, and user interfaces use IP networking and WiFi IP networks. Further down the control chain, however, many vendors are using less widely accepted or proprietary wireless network standards, and interoperability could be a problem when it's time to replace those controllers or expand the network. The recent ASHRAE announcement that a proposed BACnet over ZigBee amendment is out for public review.

CSE: Wireless controls typically work best in open environments that do not interfere with or absorb RF energy. But what technological advances have been made to wireless controls so they may be installed in other environments?

LANE : One of the latest developments in wireless control technology is minimal powered mesh networks. Wireless mesh networks are a multi-hop wireless system where devices help each other to transmit packets through the wireless network. The mesh network is particularly robust in poor conditions. A technician can install the mesh networks in place with negligible preparation. This wireless network is an ad hoc, multi-hop network. Manufacturers recently have incorporated mesh technology networking to reduce the chance of signal interruption.

KOHL : Advances, such as the IEEE 802.15.4 standard radios and mesh networking, offer promising solutions for overcoming these issues. They are being designed to coexist with other wireless devices and provide redundant, self-healing network topologies.

CSE: Where do you see the future of wireless controls?

KOHL : Concerns over reliability and security will fade as technology matures and interoperable solutions become available.

TOM : I see wireless controls occupying a significant percentage of the controls market in the future, but I don't see them completely replacing conventional wired controls. Wireless controls can provide a less expensive alternative to wired controls in many situations, but functionally they serve the same purpose and provide no operational advantage.

KUHLMAN : I see the future for wireless in small control systems where it is easier to have an isolated RF network. Control technology allows for building systems to be optimized for efficiency. For commercial systems it allows controls systems to be implemented at a lower construction cost.

LANE : Wireless will continue to grow in out industry. For instance, wireless controls transform traditional office lighting into a wireless lighting communication and control infrastructure. Additional controls including lighting and temperature controls will allow the building occupant to have more control of their environment. The wireless systems will probably by more prevalent in “smart” LEED projects. Some of the potential points and related wireless controls strategies include the following:LEED Credit 6.1 (Controllability of Systems) has the intent of “providing a high level of thermal, ventilation and lighting system control by individual occupants”.

The potential technologies and strategies for this LEED point include designing the building with occupant controls for airflow, temperature and lighting.LEED Credit 7.1 (Thermal Comfort) has the intent of providing a thermally comfortable environment that supports the productivity and well being of the building occupants. The technologies include establishing temperature and humidity comfort ranges and design the building envelope and HVAC system to maintain these comfort zones. LEED Credit 7.2 (Thermal Comfort%%MDASSML%%Permanent Monitoring) These point adds the requirement of installing and maintaining these comfort ranges and providing monitoring systems in the building to automatically adjust building conditions.

CSE: What problems do wireless controls overcome, in regard to building space? Technology?

KUHLMAN : Cabling is still required from the network to the wireless access points. Wireless access points needs to be placed throughout the areas that serve clients/devices. A small commercial building may need only one or two access points. A single tenant, multilevel building will have many more access points and it will require more work to coordinate the RF traffic with any IT wireless services in the building. Wireless controls make sense for non-critical applications. In a PLC-SCADA environment, it makes sense to use for SCADA data traffic but it is not something I would recommend from the PLC down to the I/O.

KOHL : Wired controls require a significant amount of labor to install or relocate, especially in existing buildings. Wireless minimizes installation labor. The wireless advantage is even greater on devices like room sensors, which may need to be relocated during the life of the building due to unexpected use or frequent refiguring of spaces. The ability to effectively control buildings is dependent on the sensing accuracy and sensing accuracy depends on location.



Participants

Jim Kohl

Senior Product ManagerTrane Commercial SystemsPiscataway, N.J.Tim Kuhlman, PE, RCDD

Electrical EngineerCH2M HillPortland, Ore.

Keith Lane , PE, LEED AP

Principal/PartnerLane Coburn & Assocs. LLCSeattle

Steve Tom

Dir. of Technical Information

Automated Logic Kennesaw, Ga.

Ask the experts: wireless controls

Every month, Consulting-Specifying Engineer editors ask a distinguished panel of experts for information about how to best solve your problems, challenges, and new engineering issues. At CSE gives its readers and Web visitors the opportunity to pose questions directly to the panelists. Below is a question for May's topic, specifically about wireless controls.

“While wireless has some advantages in existing structures, in a new building would it not be less expensive to install a digital control wire between fixtures? ”

Andrew Penny , President, Kingsford Consulting, Ottawa, Canada

KEITH LANE : The cost of running wire for sensors in buildings is 50%-70% of the cost of the sensor. Wireless communications could eliminate much of that cost. As the wireless technology improves and the costs of the individual points comes down, the feasibility and cost of going wireless will continue to improve.

JIM KOHL : Wireless does merit careful consideration in new construction. It is a misconception to think that wireless hardware automatically carries a high-cost premium — and any differential can often be offset by labor savings. Accounting for the labor to relocate sensors can make total cost of ownership comparable or even lower than using wired controls.

TIM KUHLMAN : This all depends on the type of building, building construction methods and how far along a building owner has come in integrating a building management system with the rest of the IT system. In a single occupant building the IT group has most likely planned for a pervasive wireless network. However, in a multi-tenant building it isn't practical to have a building management system supported by the local tenants. In this case a wired solution is more practical.

STEVE TOM : While I think the cost advantage of wireless controls is much greater in a retrofit application, they can be less expensive to install in new construction as well, particularly when you're using battery powered zone sensors or thermostats. Higher up the control chain you need external power for the controller and actuators, and pulling communication wires does not usually add much additional cost over the expense of providing power wiring. If you can run the device on a battery, however, there is no wiring required and the installation cost can be significantly lower.



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