Wireless building controls
Creative use and selection of wireless devices can potentially reduce construction costs, decrease construction time, and add future flexibility to buildings.
By Michael A. Culver, PE, exp U.S. Services Inc., Maitland, Fla.
1. Better understand some of the more common wireless technologies used in building controls
2. Learn about common wireless standards
3. Identify the potential cost savings, construction efficiencies, and flexibility that wireless controls can bring to a building
Want to offer your clients more for less? Then go wireless. By leveraging the flexibility of wireless control devices to handle the unpredictable futures of buildings, engineers can offer their clients more options. In today’s environment of ever-changing technology and increasingly more stringent energy codes, flexibility is more valuable than ever. Many of these wireless controls use miniature batteries with a claimed life of up to 10 years; some don’t even use batteries and instead use energy harvesting technology. Wireless controls may fit the ticket and may even save on project construction costs and construction schedules. Wireless controls have been around for a long time, but now that wireless has become personalized (iPhone, iPad, Android), it is easy to add another level of control that is more mobile and more personalized in many cases.
There are several competing wireless technologies in North America. The most prevalent are:
· Clear Connect, Lutron Electronics Co. Inc., primarily 434 MHz
· EnOcean, EnOcean GmbH, primarily 315 MHz
· ZigBee, ZigBee Alliance, primarily 2400 MHz (2.4 GHz)
· Z-Wave, Z-Wave Alliance, primarily 900 MHz
· A registered trademark of Lutron, which licenses to other manufacturers such as AMX and Hubbell Wiring Devices.
· Operates in frequency bands that do not allow devices that continuously transmit (like phones and Wi-Fi routers) and is therefore less susceptible to interference.
· Operates at lower frequencies, which allows better transmission through heavy building materials.
· 434 MHz in Americas; 868 MHz in Europe, Middle East, and China; 315 MHz in Japan; and 865 MHz in India.
· Protocol is optimized for sending small amounts of data very quickly to many devices over a large area--provides superior response time from devices.
· Protocol is optimized for long battery life.
· In market since the late 1990s.
· Trademark of EnOcean GmbH.
· Operates primarily on 315 MHz, (868 MHz in some areas).
· EnOcean Alliance agrees to a set of profiles (somewhat similar to ZigBee) and sets the application layer of the protocol.
· Focused on energy harvesting—wireless and non-battery-powered technology.
· Used by Electronic Theatre Controls (ETC) in its Unison Aero line along with many other manufacturers.
· ZigBee is a registered trademark of the ZigBee Alliance, a non-profit association of manufacturers, which maintains the ZigBee Standard.
· Manufacturers have to become a member to make and market ZigBee products for commercial use.
· Operates primarily on 2.4 GHz (worldwide frequency), but 915 MHz and 868 MHz also available.
· Built on and uses physical and access layers of the IEEE 802.15.4–2003 protocol.
· First standard—called ZigBee 2004—has been around since 2005 and has been updated and revised several times since publication.
· The ZigBee Alliance sets and publishes Application Profiles to help manufacturers make interoperable products, including:
· ZigBee Commercial Building Automation
· ZigBee Home Automation
· ZigBee Smart Energy 1.0
· ZigBee Telecommunication Services
· ZigBee Health Care
· ZigBee RF4CE - Remote Control
The ZigBee Commercial Building Automation Profile relies on a ZigBee ”Pro Stack” profile and focuses on large commercial buildings. The profile provides for wireless connectivity of building HVAC systems, building automation system (BAS) controllers, lighting controllers, and other devices within a commercial building. The profile brings together ZigBee and Building Automation and Networking (BACnet) protocol, which is a standard for building automation communications. For additional information, refer to www.zigbee.org/Standards/ZigBeeBuilding Automation/Features.aspx
· It is important to note that to ensure interoperability between various devices and equipment using the ZigBee standard, customers must make sure the products use the same ZigBee profile.
· Operates primarily on 900 MHz, and also 868 MHz.
· Mainly residential, but some light commercial applications.
· Z-Wave Alliance formed and many manufacturers make products that use the Z-Wave standard.
To determine potential cost savings when selecting a product to be used in a building, consider looking deeper than hardware and labor costs. Many other costs can come into play when evaluating initial building and construction costs: retrofit costs, flexibility costs, and occupant comfort.
Hardware costs: Hardware costs for items like switches, conduit, boxes, wire (low voltage of 12 to 24 V and line voltage of 120 to 277 V), occupancy sensors/power packs, and temperature sensors can add up quickly. The hardware costs for the wireless devices typically will be greater than the costs for the wired counterparts they are replacing.
Soft costs: Cost savings for items like occupant comfort and control are harder to quantify cost-wise. However, it is not a stretch to attribute occupant comfort to increased productivity and company retention rates. For example, consider a large, open office space with cubicles where the only permanent walls are around the perimeter of the space (sometimes these are movable walls that are part of the office furniture system; see Figure 1). It is quite common to place temperature sensors around the perimeter, hardwired in the permanent walls. In many cases, temperature sensors for different zones are placed on the wall next to each other to help save on construction costs. But when a temperature sensor is not located in the zone that the HVAC system serves, inaccurate temperature sensing can result in the actual location where the HVAC unit is providing cooling/heating. Moreover, when the temperature sensors are ganged together on the wall, often there is confusion as to which temperature sensor controls which area. Wireless temperature sensors can easily be located at the point of use, even on a movable wall or on a partition within an employee’s cubicle. Lighting controls with dimming and personal control at each workstation also help to improve employee comfort and productivity.
Employee comfort has a definite correlation to productivity and retention rates for companies, as shown in a white paper titled “Environmental Satisfaction, Personal Control, and the Positive Correlation to Increased Productivity” prepared by Carol Lomonaco and Dennis Miller from Johnson Controls Inc. This study indicates that giving employees control over their comfort gave nearly a 3% productivity boost. Furthermore, according to this white paper, indoor air quality (IAQ) and comfort has up to a 60% impact on productivity levels. Other studies indicate that the cost per square foot of salaries in an average facility is anywhere from 8 to 13 times the cost per square foot of building operations, often topping $200 per square foot, per person, per year. It is easy to correlate the significance of employee comfort costs as compared to a building’s operating costs because the employee costs are significantly higher.
Flexibility: Flexibility cost savings can be encountered not only during but also long after the construction of a new building. During new construction, it is quite common for the building design to morph due to construction conflicts or owner directed changes to the design. These changes often lead to material and labor waste because walls are sometimes relocated or devices have to be roughed in again and rewired. After the building is constructed, there might be a need for additions, moves, and changes, or complete building or space renovations. Wireless devices rarely get in the way because they are easily removed with two screws and in some cases peel-and-stick adhesive strips. Relocation of these devices is measured in minutes, not hours, and does not require skilled labor in most cases.
Construction schedules: During new construction or renovations, maintaining a construction schedule can prove to be very challenging. Scheduling the various trades to rough-in conduit and boxes prior to installing drywall does not always go as planned. In successful building construction, many hours can be spent on coordinating these rough-ins so that they don’t conflict with doors and furniture. Because no conduit or boxes are required, wireless solutions can reduce the coordination time during the rough-in phase and thus speed up construction. Because wireless devices are installed near the end of construction, each device location is touched only once for the final installation. Additionally, in the case of temperature sensors, the HVAC contractor does not have to wire the low-voltage wiring and then return at a later date to install and terminate the wire in the sensor. As wireless technologies become more commonplace in building construction and renovation, schedules can be impacted in a positive manner, creating a win-win situation for both the contractors and building owners.
Labor savings: Similar to construction schedule cost savings, significant labor savings costs can be reaped by owners and contractors for many of the same reasons. It is estimated that wireless devices can save up to 50% of physical labor costs. This can be translated into reduced project costs and increased contractor efficiency because fewer workers are required to be on-site. Labor savings could vary drastically depending on whether local codes require the low-voltage wiring in conduit or whether labor rates reflect union versus non-union areas.
Design and engineering costs: Other than having to pay attention to building construction types and the effect they have on distances between receivers/repeaters and the wireless transmitters (i.e., switches, sensors, etc.), there is little impact, positive or negative, to the design engineer when using wireless products. Once the devices are incorporated into the design specifications, the only impact on design might be fewer wiring details. However, engineers should consider buildings with special construction where a radio frequency (RF) study may be warranted to ensure proper wireless penetration.
When the traditional hardwired system approach is compared to a wireless approach, accounting for all wireless hardware costs and all other cost savings, the overall installed cost for a wireless solution is comparable or even less than that for a wired system.
Consideration should also be given to some of the maintenance costs of wireless sensors as compared to hardwired counterparts. Many wireless sensors require battery replacement; some replacement schedules are as long as 10 years. The maintenance cost of replacing the batteries in hundreds or even thousands of wireless sensors in a facility is not negligible. Sensor failure due to a low battery or signal fade or loss could compromise occupant safety or equipment/property damage. Risk and reliability may also be considerations. There may be buildings where this risk is not feasible.
Cost savings will always vary based on the project type, local labor rates, and how well the contractors are educated on the efficiencies of using of wireless technologies. For medium to large projects, Trane reports that its wireless solution is priced to save an average of 10% of the installed price compared to a traditional wired solution. This does not include the soft or flexibility costs that can be further achieved throughout the building’s lifecycle. Lutron, for example, has reported that on a recent project in New York City, the devices that were shifted from wired to wireless took 70% less installed cost (labor and materials). The overall project, including fixtures and other wireless controls, achieved 17% savings over a wired equivalent. In individual office spaces with a switch and occupancy/vacancy sensors, the cost savings can be in the range of 20% ($15 to $60 per office, depending on the labor rates). The higher the labor rate, the better the savings.
With the world going more wireless every day, the “cut the cord” statement continually loosens and morphs from the cable TV and phone industries to almost any device category you can think of. As wireless technologies continue to evolve and are incorporated into more devices, it will be more important to understand the cost savings and other benefits during the bidding process. Building owners, design engineers, and contractors all will benefit from the increased efficiencies, cost savings, and flexibility that wireless devices offer.
As the wireless standards continue to develop, emphasis will continue to be placed on a friendly wireless ecosystem where all devices can live in the various wireless spectrums and be good neighbors. With the various wireless standards organizations, there are opportunities for manufacturers’ devices to communicate within the standards “sandbox.” However, because there are competing standards, paying attention to the details when specifying and reviewing submittals will continue to be important when integrating different manufacturer’s components.
Adhering to energy codes
ASHRAE Standard 90.1-2010, Energy Standard for Buildings Except Low-Rise Residential Buildings, has new, very challenging requirements. According to an Oct. 19, 2011, ruling by the U.S. Dept. of Energy, all states will be required to certify that the provisions of the state’s commercial building codes have been updated to include the requirements of the 2010 version of Standard 90.1 standard by Oct. 18, 2013.
One of the new additions to the standard is a requirement for automatic control of 15- and 20-amp receptacles in private and open offices and computer classrooms. Specifically, the standard states:
8.4.2 Automatic Receptacle Control: 125 V 15- and 20-Amp receptacles, including those installed in modular partitions, installed in the following space types:
a. Private offices
b. Open offices
c. Computer classrooms shall be controlled by an automatic control device that shall function on:
a. A scheduled basis using a time-of-day operated control device that turns receptacles off at specific programmed times—an independent program schedule shall be provided for areas of no more than 25,000 sq ft but not more than one floor, or
b. An occupant sensor that shall turn receptacles off within 30 minutes of all occupants leaving a space, or
c. A signal from another control or alarm system that indicates the area is unoccupied.
Casino expansion goes wireless
In the Great Smoky Mountains National Park in North Carolina, the Harrah’s Cherokee Casino and Hotel has almost completed a world-class expansion project worth more than $500 million. The 985,000 square foot expansion, due to be 100% completed before the end of the year (first phase of this expansion opened June 2010), included a new third hotel tower, 3000-seat events center, a significant expansion of the casino area, and a high-end luxury spa. As one can imagine, the last thing the public space designers wanted to deal with was controls conduits flying over, under, and on the highly themed finishes in the public spaces.
exp and Trane worked together to find a solution that not only solved the conduit challenges, but also saved the project both time and money. The wireless sensor solution required that the normal controllers in each HVAC unit, terminal box, etc., incorporate a controller with a wireless receiver. Each controller/receiver combination can easily communicate wirelessly to sensors throughout the space within a 200 ft radius. (The dedicated wireless receiver per HVAC unit provides redundancy and eliminates the chance of one receiver failure affecting the control of multiple HVAC units, plus it adds local communication at the controller directly to the wireless receiver.) The new construction and expansion used roughly 870 of Trane’s WTS series wireless temperature sensors with an estimated installed cost savings to the project of roughly $106,000. This does not include any additional cost savings from devices that were easily relocated without having to rewire, therefore reducing construction change orders.
This project involved many phases of construction to keep the existing facility in operation and maximize the amount of gaming floor in operation at all times. This resulted in fast construction for each phase, which made the choice to go with a wireless solution very beneficial.
Office building upgrades
Trying to upgrade a nearly 30-year-old existing building to make it more energy-efficient can prove to be challenging and costly. To complement the more intensive HVAC energy savings upgrades already implemented, exp engineers decided to also look at low-hanging fruit on their own building in Maitland, Fla. They determined that a relatively quick and painless upgrade would to be to add wireless occupancy sensors throughout the 30,000-sq-ft facility.
There were two solutions that were considered for the retrofit. The first and more traditional solution would involve hardwiring a remote power pack to the line voltage side of the circuit serving each office and then running low-voltage wiring from the power pack to the respective ceiling-mounted occupancy sensor. In areas like personal offices, a wall switch type occupancy sensor was also considered, eliminating the power pack and associated wiring.
The second solution involved a wireless solution. If the wireless approach was going to be used, the requirements for the exp-owned and occupied office building were simply to replace existing light switches that communicate with a wireless occupancy/vacancy sensor. In addition, due to the open office layout, flexibility was required to easily move and/or add devices for full coverage.
It gets complicated really fast: Some manufacturers use a wireless relay that is hardwired into the lighting circuit above the ceiling, which communicates wirelessly to a wall-mounted wireless switch. In addition, the wireless occupancy sensor is wired to a transmitter hub that is line powered above the ceiling. Other manufacturers have wireless switches but do not have occupancy/vacancy sensors. Some manufacturers require low-voltage lines run between switches that are powered from a line-powered wireless hub.
The final solution simply involved a light switch replacement that incorporated a wireless receiver that talked to a battery-powered, ceiling-mounted wireless occupancy/vacancy sensor that can be easily placed. This solution uses the same approach to add daylight sensors to an area.
The choice came down to cost and ease of installation. The installation could be done by in-house maintenance staff because it was a simple wall switch replacement. Aesthetics also came into play. The team chose Lutron’s Maestro wireless switches that communicate wirelessly with the battery-powered ceiling Radio Powr Savr occupancy/vacancy sensors. In about 15 minutes per location, the existing, traditionally wired light switch was replaced with the wireless switch. Programming the link between the two was done simply by pressing two buttons. For three-way switches, peel-and-stick Lutron Pico battery-powered wireless switches were used with a traditional rocker switch-type faceplate. Daylight sensors were also added to the atrium areas in the same manner as the occupancy/vacancy sensors.
The other benefit to the selected choice was the aesthetics. The light switches appear and function like traditional rocker-style switches with no sensor lenses protruding or being able to be poked in. The ceiling sensors (3.51 in. diameter) were adhered using the provided adhesive strip, which allowed sensors to be moved around as required for coverage without having to patch holes in the ceiling, making the in-house maintenance staff happy. Because the wireless sensors use low power technologies, which have a 10-year lifespan between battery changes, the cost and frequency of maintenance is reasonable and easy on the operating budget. After more than a year of use it was clear that the wireless choice was a good one as it allows the maintenance staff to focus on other areas of the building.
Michael A. Culver is a principal at exp U.S. Services where he focuses on technical specifications and building designs in the hospitality, entertainment, and mission critical fields.
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