My contribution to the October 2021 issue of tED Magazine covered growing demand for plug load control in new buildings, a need that can be handled by lighting control systems. Reprinted with permission.
In the past 15 years, commercial building energy codes increasingly incorporated automatic control of lighting loads. While the combination of LED lighting and detailed control strategies dramatically curbed lighting’s share of building energy consumption, code makers started to address plug loads, a substantial load and the fastest-growing type. Again, lighting controls can help by integrating plug load control.
The problem
Plug loads include any devices that plug into standard electrical receptacles, such as task lighting, computer printers, photocopiers, cell phone chargers, personal fans/heaters, and appliances like coffeemakers. Many applications feature plug loads, though office buildings are quite intensive.
A great deal of office equipment is used intermittently during operating hours and not at all overnight. Equipment with enabled standby mode will go idle but still draw power. Even equipment that powers to Off may continue to draw a small amount of power as long as it’s connected to a socket, so as to be able to restart quickly; this is called a vampire, phantom, or parasitic load.
Plug and process loads accounted for 40 percent of commercial building energy consumption in 2017, according to the Department of Energy. A study estimated plug loads ranging from 25 percent in an overall less-efficient building to 50 percent in an overall high-efficiency building.
A solution
Image courtesy of Leviton
By automatically removing these devices from power when they’re not being used, significant energy savings can result, ranging from 20 to 50 percent. A 2012 General Services Administration office building study found that even with standby mode enabled, automatic receptacle control captured significant energy savings ranging from 26 percent in workstations to nearly 50 percent in kitchens and printer rooms, with highest savings for 24/7 devices such as printers, copiers, and kitchen appliances.
The energy savings were compelling enough to convince code makers to adopt the strategy. California’s Title 24, Part 6 and codes based on ANSI/ASHRAE/IES 90.1 (2010 and later) and the 2021 version of the International Energy Conservation Code (IECC) require automatic receptacle control. Specifically, a significant portion of receptacles in certain spaces be automatically controlled by scheduling, occupancy sensing, and/or automatic signal from another building system. The lighting control system offers these inherent control capabilities that can accommodate plug load control. Hotel and motel guest rooms have separate but similar requirements.
“Integrating plug loads with the lighting controls makes sense because it reduces the number of devices that need to be installed and therefore the cost and complexity of the total system,” said Charles Knuffke, Systems Evangelist, Wattstopper/Legrand (www.Wattstopper.com). “Instead of having separate timeclocks or occupancy sensors for the lighting and plug load controls, a single input device can communicate to both lighting and plug load controllers.”
He added that one set of inputs makes it easier for the owner to understand and manage their operations. If a networked control system is installed, the sensors can serve lighting, plug load, and HVAC control.
Options
When enacted by the lighting control system, a plug load control solution uses scheduling, occupancy sensing, or a combination of the two (e.g., scheduling during day, sensing at night), depending on the system.
Scheduling is relatively simple and well suited to larger, open applications with predictable occupancy and loads that must remain On during business hours even when they’re not being used. A manual switch on the receptacle or nearby wall provides user override up to two hours.
Occupancy sensing is based on detected rather than predicted occupancy, which can generate higher energy savings. This approach is ideal for smaller, enclosed spaces where occupancy is intermittent and unpredictable. If the sensor is auto-On, it can function as its own override.
The controlled load is the receptacle, able to respond to a control signal or fed power by a branch circuit that can respond to the signal. Some wirelessly controlled receptacles also feature onboard power metering. In a duplex receptacle, both outlets can be controlled or just one, allowing the uncontrolled outlet to operate loads that must remain On. Energy codes require controlled receptacles be permanently marked to distinguish them as controlled; starting in 2014, the National Electrical Code produced standardized markings for use.
“Contractors and facility managers will want to ensure a balance between efficiency and convenience, installing well-marked, controllable receptacles in locations that are reserved for loads like task lighting, small appliances, and small electronics such as heaters and monitors not designed for 24/7 use,” said Devis Mulunda, Product Manager – Vive Wireless, Lutron Electronics (www.Lutron.com).
Image courtesy of Lutron Electronics
These automatic receptacles can operate independently, as in the case of onboard timer/timeclock functionality for scheduling, or be controlled as just another load by the otherwise installed lighting control system: controllable circuit breaker panelboard, lighting control relay panel, or a relay in a dedicated powerpack. The system may be wired or wireless. If the overall control system is networked, power metering can be achieved and there is potential for more sophisticated dashboard control. Plug-in advanced power strips can be effective for retrofit but are not code-compliant for a new build.
“The implementation strategy varies based on what type of technology you are deploying in the room,” said David Buerer, Director of Product Management, Leviton Manufacturing Co., Inc. (www.Leviton.com). “If your solution is wallbox sensors, then it can be as simple as adding a second wallbox sensor control receptacle. If ceiling sensors and power packs, then adding a second power pack in auto-On mode. If more of a system, then you’ll be adding a wireless controlled receptacle, smart pack, wireless powerpack, or the like to gain receptacle control.”
Buerer added that after installation, it’s important that users be educated about the purpose and operation of the controls and how to identify which outlets are controlled, which will help ensure acceptance.
Final word
“Since plug load control is required by energy codes, the electrical distributor’s customers will be looking to the distributor to define what the code’s requirements are, offer products to meet the code, and explain the many features and benefits of the methods that can provide plug load control,” Knuffke said. “Look for manufacturers that can provide a range of solutions: relay panels, plug load powerpacks for simple component solutions, plug load controllers for intelligent systems, and controllable outlets. Ask if controls are available that use wired and/or wireless communication.”
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