Adoption of ANSI/ASHRAE/IES 90.1-2010 places greater importance of lighting controls in energy-efficient building design
In the not-so-distant future, building owners who manage to drastically trim energy usage by implementing advanced lighting control schemes will inevitably have an edge when it comes to cost savings, sustainability, and possibly even compliance with certain codes and standards. By 2025, for example, the U.S. Department of Energy (DOE) has made it a goal to achieve zero-net energy in commercial buildings through the creation of successively more stringent standards, which could theoretically be adopted by individual states.
In response to expanding energy legislation and regulations, lighting equipment manufacturers have raised the performance bar for both linear fluorescent lamps/ballasts and HID lamps/ballasts over the past few years. Now it’s time for lighting controls to push energy savings even further and make the goal of “zero net” a reality.
Recent advancements in technology, coupled with the looming possibility of more stringent energy management mandates, offer savvy electrical contractors an opportunity to bring value-added ideas to their commercial customers on the lighting control front.
The Department of Energy adopted the ANSI/ASHRAE/IES 90.1-2010 standard (a document that focuses on dramatically reducing unnecessary lighting energy use) as the national reference standard on Oct. 19, 2011. States have until October 2013 to update their commercial building energy codes to meet or exceed the requirements of this document. The standard effectively limits the lighting power density (LPD), or watts per sq ft, for an entire building and for individual types of space. It also greatly expands the need for lighting controls compared to the previous version (2007). By implementing the provisions of the 2010 standard, with its greater energy restrictions, building owners may be able to gain 18% more energy savings compared to the earlier version.
For example, with the 2010 standard, if a retrofit lamp/ballast system is installed for more than 10% of the connected lighting load in an indoor or outdoor area, this fact may trigger other code compliance requirements. This could include LPD limits and automatic shutoff requirements, such as the addition of
occupancy sensors or some other control method. In the older 90.1-2007 standard, a retrofit project involving alteration to more than 50% of the connected lighting load was needed to initiate compliance requirements.
A quick review of the new standard indicates that buildings must have automatic lighting shutoff, covering both indoor and outdoor lighting with all interior automatic controls restricted to manual-on or auto-on to 50% operation, bi-level switching for stairwells and certain spaces, occupancy sensors in a broad range of space types, and daylight harvesting in areas that receive daylight.
In the 2007 version of the standard, buildings smaller than 5,000 sq ft did not have to comply with any automatic lighting shutoff requirements. However, all buildings — regardless of size — must now comply with this provision. This can be accomplished through scheduled shutoff (time-of-day) from time clocks or similar devices connected to a central control panel, occupancy sensors (time delay of 30 min. maximum), or a signal from another control system. In addition, lighting controls must be configured to manual-on operation, or, if automatic-on is desired, the room must be wired and controlled in such a way to ensure no more than 50% of the general lighting will turn on automatically.
The 2007 standard called for an occupancy sensor or a time switch to turn lighting off within 30 min. after the last occupant leaves a classroom, conference room, or employee lunch room (break room). Under the 2010 standard, 10 different types of spaces (including lecture halls, restrooms, and all offices over 250 sq ft) must comply. The occupancy sensors and time switches must be configured to either manual-on or auto-on to 50% or less to comply with the “additional control requirements” provision.
Light Level Reduction
Although not required in the 2007 standard, enclosed spaces have to be able to drop the power level by 30% to 70% of full connected load in addition to turning off the entire lighting load in the 2010 standard. Also new in 2010, lighting equipment in parking garages must have a method to automatically shut off. In these areas, the connected power to lighting must be reduced by at least 30% automatically when motion is not detected within 30 min. Lighting fixtures close to the perimeter of a parking garage structure must also use automatic daylighting control.
Let’s take a look at how these critical lighting control schemes are coming of age in response to codes, which are based on societal mandates.
Gaining Flexible Control Systems
As LPD levels continue to drop in response to legislation and the increasingly stringent standards (e.g., 90.1-2010, California’s Title 24-2008, and the 2009 Washington State Energy Code), having more granular zoning in office space makes distributed control schemes more desirable. Today’s lighting equipment increasingly has network communications capabilities. Adding communications chips to ballasts and drivers permits a wide range of control options, including on/off switching, dimming, and 2-way communications for verification of a control function or the status of lamps and ballasts.
Although hardwired switching and occupancy sensor devices are relatively economical, they are inflexible. For example, a 0V to 10V dimming system lacks active feedback and suffers from voltage variations. One solution available since 2004 is a digital lighting control system using components compatible with the Digital Addressable Lighting Interface (DALI) protocol. A complete DALI system consists of a bus hub and sensors, ballasts, and input ports connected on a simple 2-wire bus circuit. Because it uses an industry-standard protocol (open source language), DALI-compliant components from different manufacturers (ballasts, sensors, and switches) can be used together.
Although DALI buses are limited to 64 nodes (individual addresses), multiple buses can be used. A computer can be added to interconnect buses and allow inter-bus communication. Up to 16 different light levels, fade times, and rates can be stored in the ballast memory. Circuit and lighting schemes are defined and changed by software control — not by hardwiring, which makes for easy configuration and modification.
Although a DALI system may be more expensive than a traditional system, the lower cost of installation and the more simplistic wiring scheme must be factored into the overall equation. In a DALI system, the commissioning process (see System Commissioning), which involves assigning addresses and storing the control information using software, has particular importance. Thus, the respective manufacturers’ instructions should be followed precisely.
Gaining increasingly more industry attention, “tuning” is a control function that is possible with a DALI system. A lighting system is often designed to over-illuminate a space. This assures that, even as light output diminishes over the course of a lamp’s life (called lumen depreciation), light levels will remain adequate. A tunable lighting system trims the initial light level to the design light level throughout the lamp’s lifetime.
Digital lighting control is particularly useful in applying daylight harvesting, where daylight enters a space through a window, skylight, or atrium, thereby reducing — or sometimes even eliminating — electric lighting. Increasing awareness of green construction, particularly Leadership in Energy and Environmental Design (LEED) projects, and other education factors are helping in gaining greater market acceptance of this technique as well. While step dimming is similar to bi-level switching in the effect achieved, continuous dimming equipment achieves a smooth change in light level across a specific dimming range and is just about imperceptible to the human eye.
Some manufacturers have taken a slightly different approach to the use of DALI-based protocols to build what they would call an “integrated” control solution. One manufacturer with an essentially DALI-based product line, for example, uses a PDA/smart phone device to do system configuration. Another has a system that looks similar to DALI but offers a simpler zone-based solution. Yet another has a sensor and control unit built into the luminaire. A final example is a fully proprietary system that offers the most direct and easiest to install solution but limits product selection greatly.
With all of the complexity in control systems today, there is a ray of hope for some simplification in design and placement — wireless control.
One concept that comes up when specifying a detailed lighting control system is to offset the cost of the system by reducing the cost of equipment and wiring, as well as the time and labor normally associated with commissioning such a system. One alternative is to use a wireless radio frequency (RF) control system, using devices such as occupancy sensors, photosensors, low-voltage relay switches, line-voltage controls, hotel card switches, shade controls, and door/window sensors. With no damage to walls or ceiling — and little or no disruption to activities in an office — wireless control is ideal for use in existing buildings that need advanced lighting control. In the simplest RF system, a sensor, such as an occupancy sensor, communicates to a controller that serves the load, such as a wall switch that contains an embedded RF receiver.
Wireless control devices may be powered by batteries (offering a rated life of up to 10 yr) or through energy “harvested” from the operating environment, such as ambient light or temperature changes. In another case, the simple motion of pressing a light switch creates enough energy to send a control signal to a receiver.
When a large number of loads and/or a variety of control strategies have to be handled, a mesh network is generally used. In this type of arrangement, control signals are passed along, or routed among, all of the wireless devices that make up the system (each one is called a network node). Thus, multiple, redundant pathways are provided for the signals to get to their intended receiver(s). Mesh networks are “self-healing,” meaning if one of the devices is not working, the signal is routed through another device that is functioning.
All of the RF control devices in an installation must be interoperable, meaning that they must be compatible with one of the four main types of RF communications protocols used today: ZigBee, Z-Wave, EnOcean, or proprietary.
Sidebar: Education Opportunities for Electricians
Last fall, the New York section of the IESNA drew about 500 architects, lighting designers, engineers, and technology professionals to a day-long event called “Control This,” which offered the latest developments in lighting control and energy management ideas. The event featured more than 40 tabletop displays of lighting control solutions being offered by manufacturers and a series of educational seminars. One workshop, which allowed participants to wire a simplified lighting control system, was a shorter version of a 50-hr course for journeymen electricians, called California Advanced Lighting Controls Training Program (CALCTP), in which Steve Mesh, a lighting consultant and educator, has been one of the main instructors and developers (see www.calctp.org). The course was initiated by Southern California Edison in conjunction with industry and academic partners (NECA/IBEW, California Community Colleges, etc.) and is backed by the major California utilities. To date, more than 1,000 electricians have competed the course, and utilities will be offering incentives for projects in which installing electricians have been certified by the CALCTP course.
Sidebar: System Commissioning
A third party, not connected with the design and construction of the project, must test and verify that a lighting system is calibrated, adjusted, and operates according to the manufacturer’s requirements. Afterward, the party responsible for testing and verification must submit documentation stating that the controls meet or exceed the performance criteria.
A corollary to the commissioning phase is the need for specific documents to be turned over to the owner within 90 days of system acceptance, including as-built drawings of the lighting and control system, operation and maintenance manuals for all lighting equipment, a recommended schedule for relamping, and a schedule for inspecting and recalibrating the lighting controls.
Programming and commissioning costs are usually included in system specifications and factored into an estimate. Generally, someone on the design team provides a detailed description of the functions that the luminaire provides, and that documentation should be as accurate as possible. The wording of this “control narrative” may change as the project moves forward in time from design to construction to occupancy.