Office plug loads are the loads with the largest power density (W/ft2) in most office buildings. The Energy Standards require both controlled and uncontrolled 120-volt receptacles in lobbies, conference rooms, kitchen areas in office spaces, copy rooms, and hotel/motel guest rooms. The requirement of the Energy Standards for controlled receptacles allows these plug loads to be turned off when the space is unoccupied, resulting in energy savings.
In the 2016 update to the Energy Standards the requirements for circuit and receptacle level controls for 120-Volt receptacles have been clarified. Either approach can be used, provided that controlled receptacles are marked to differentiate them from uncontrolled receptacles.
Methods for meeting requirements include:
1. For any uncontrolled outlets, ensure that at least one controlled outlet is located within 6 feet of the uncontrolled outlet.
2. Using split wired receptacles that provide at least one controlled outlet.
The requirement does not mean that one controlled outlet must exist for each uncontrolled outlet.
In open office areas where receptacles are installed in modular furniture, at least one controlled receptacle must be provided for each workstation. Alternatively, any controlled circuits already built into the building system can be used to meet the requirement.
The controlled receptacles must be automatically switched off when the space is not occupied. An automatic time switch with manual override may also be used for meeting the requirement.
Plug-in strips and other plug-in devices CANNOT be used to meet this requirement. A hardwired power strip controlled by an occupant sensing control may be used for meeting the requirement, but a plug-in power strip cannot be used: the intent is for the controlled receptacles to be permanently available, not removable.
There are important exceptions where an uncontrolled outlet is not required to be matched with a controlled outlet. They include:
1. Receptacles in kitchen areas that are specifically for refrigerators and water dispensers.
2. Receptacles specifically for clocks (note that the receptacle must be mounted 6’ or more above the floor to meet this exception).
3. Receptacles in copy rooms specifically for network copiers, fax machines, A/V and data equipment other than personal computers.
4. Receptacles on circuits rated more than 20 amperes.
5. Receptacles connected to an uninterruptible power supply (UPS) that are intended to be in continuous use, 24 hours per day/365 days per year and are marked to differentiate the receptacles from other uncontrolled receptacles or circuits.
The following are example approaches:
A. Private Offices, Conference Rooms, and other Spaces with Periodic Occupancy
Occupancy sensing controls that are part of a lighting control system may be used to control both general lighting and receptacles. For example, a common occupancy sensor can control general lighting and receptacles, with auxiliary relays connected to the lights and the controlled receptacles to provide the needed functionality.
B. Lobbies, Break Rooms, and other Spaces with Frequent Occupancy During Business Hours
Astronomic time-switch controls, with either a vacancy sensor or switch override, can switch the controlled receptacles. Programmable relay panels or controllable breakers can be used, or, for simpler projects, a combination of vacancy sensors and programmable time switches can accomplish the same task. Note that if vacancy sensing is used, controls will likely need to be room-by-room or space-by-space, but if time-of-day with manual override is used, whole circuits may be controlled together.
C. Open Office Areas
Receptacles in open office areas can be controlled by the building’s automatic shut-off system or by controls integrated into the modular furniture systems. If the building provides controls, relays or controllable breakers with manual override switches for zones within an open office space may be used. A system using vacancy sensors might also be considered if sensors can be added as needed to address partitioning of the workstations (thus ensuring proper operation). Systems contained within workstation systems are an acceptable alternative provided that they are hardwired as part of the workstation wiring system.
D. Networked Control Systems and Building Automation Systems
Most advanced lighting and energy control systems can be easily designed to accommodate receptacle controls.
The Energy Standards recognize that certain office appliances, such as computers, need to be powered continuously during office hours to provide uninterrupted services. These would be connected to the uncontrolled receptacles. Other appliances, such as task lamps, personal fans and heaters, and monitors, do not need to be powered without the presence of occupants. These controllable loads would be plugged into the controlled receptacles to ensure they are automatically shut off and to prevent any unnecessary standby power draw. Ultimately, providing controlled receptacles allows building occupants to determine which appliances to be controlled.
In open office areas, it is advisable to implement vacancy sensor control at each workstation or cubicle to maximize the opportunities of shutoff controls. Modular office system furniture is usually equipped with more than one internal electrical circuit, and some of these circuits can be dedicated for controllable plug loads.
The demand response (DR) requirements of §130.5(e) specify that any controls or equipment for DR shall be capable of receiving and automatically responding to at least one standards-based messaging protocol. This ensures that any DR equipment that is installed is able to receive and respond appropriately to demand response signals.
To explain, the Energy Standards provide definitions for both “Demand Response Control” and “Demand Response Signal”:
•Demand Responsive Control is defined in §100.1 of the Energy Standards as “a kind of control that is capable of receiving and automatically responding to a demand response signal”.
•Demand Response Signal is defined in §100.1 as “a signal sent by the local utility, Independent System Operator (ISO), or designated curtailment service provider or aggregator, to a customer, indicating a price or a request to modify electricity consumption, for a limited time period.”
Demand response controls can be effectively employed in many circumstances and for several different building systems. The Energy Standards require demand response controls for lighting systems in two circumstances, per the requirements of the following sections:
•§130.1(e) requires the lighting in buildings over 10,000 square feet, excluding spaces with a lighting power density of 0.5 W/ft2 or less, to be capable of automatically reducing lighting power in response to a Demand Responsive Signal; so that the total lighting power of non-excluded spaces can be lowered by a minimum of 15 percent below the total installed lighting power when a Demand Response Signal is received.
•§130.3(a)3 requires electronic message centers over 15 kW to have a control installed that is capable of reducing the lighting power by a minimum of 30 percent when receiving a Demand Response Signal.
The above requirements do NOT mean that a building has to respond to real time price signals; the requirement is to ensure that the building is DR ready (i.e., capable of responding to a DR signal). The decision to employ demand response is up to the building owner or manager, the utility company, and/or a governing authority. A building that is capable of responding to a request to reduce load when grid reliability is threatened (for instance with black outs) is sufficient to meet the requirements of the Energy Standards.
Demand response is becoming increasingly important as it permits the temporary reduction of electric load on the grid when extreme weather or supply constraints cause electricity demand to come close to the grid’s maximum supply capabilities. It is also seen as a means to allow building operators to control electricity costs, as future prices are expected to change constantly as a function of overall system demand.
Because mandatory demand response (“DR”) is relatively new, standards and systems are still being developed and evolving. For this reason, §130.5(e) does not specify a particular protocol or system, but rather lets it be specified by the utility company or other authority.