Consulting-Specifying Engineer - May 2008 - (Page 14) M/E Roundtable 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–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. 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 www.csemag.com/asktheexperts, 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. “ 14 Consulting-Specifying Engineer • MAY 2008 http://www.csemag.com/asktheexperts
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