How LEDs affect energy codes
ASHRAE Section 18.104.22.168 mandates the inclusion of a control device accessible to occupants so they can turn lighting on, off, or adjust light levels when desired. The device must be capable of reducing light levels with at least one control step between 30% and 70% (inclusive) of full lighting power in addition to all off. Again, the flexibility of LEDs for multi-level control would be a significant factor in the design process.
California has taken this multi-level control requirement even further. In Title 24-2013 (Section 130.1(b)), for rooms over 100 sq ft with greater than 0.5 W/sq ft LPD (some other exemptions apply), this multilevel requirement now mandates different lighting power levels based on the type of lighting installed. For fluorescent lamps greater than 13 W, in addition to “full on” and “full off,” three other levels are required: a low level (20% to 40%), a medium level (50% to 70%), and a high level (80% to 85%). While this can be done with other methods, many recognize that the most logical way to meet this requirement is to use continuous dimming ballasts. Interestingly, Title 24-2013 does not require multiple levels when LEDs are used for general lighting in rooms over a certain size and lighting power density. In this situation, the fixtures must be capable of continuous dimming from at least 10% to 100% power level.
Daylighting is another area where LEDs come into play. ASHRAE 90.1 (Section 22.214.171.124) has extensive requirements for automatic daylighting control in side-lit and top-lit areas; one key requirement is the capability of multiple light level reductions (at least one control step between 50% and 70% full output and another step no greater than 35% of design power). In Title 24-2013 (Section 130.1(d)), mandatory daylighting requirements will be required when the total lighting power in primary side-lit and sky-lit daylight zones is greater than 120 W.
Using lower-power LED fixtures could eliminate the need for daylighting controls if the LEDs prevent this wattage threshold from being crossed. As noted already, since LEDs offer the benefit of being easily dimmed, this may well drive the use of LED lighting sources in new construction that must comply with all the code requirements. Continuous dimming is a much less obtrusive interaction for the occupant in the space than having lighting turn completely on and off when daylight levels change in the space.
Another new requirement is that of commissioning the lighting and control system. ASHRAE Section 9.4.4 requires lighting control devices and systems be tested to ensure that control hardware and software are calibrated, adjusted, programmed, and in proper working condition in accordance with construction documents and the manufacturer’s installation instructions. This includes confirming correct placement, sensitivity, and time-out adjustments for occupancy sensors; correct programming for programmable switches or panels; and correct light level reductions by photosensors.
This functional testing and certification must be performed by a party identified in the construction documents that is not directly involved in either project design or construction. While LED fixtures currently are designed to connect to the same power circuits as other fixtures, the new technology can lead to surprises for anyone commissioning the systems—for instance, every dimmer that controls an LED fixture must be verified to be the correct type (e.g., 0 to 10 V, forward phase, reverse phase, etc.) because there is no single standard for dimming LEDs. Questions may also arise because a dimmer capable of handling a small incandescent load may not be able to handle the same load when controlling LEDs due to the LEDs’ driver circuitry.
LEDs will also find application in some of the most innovative requirements. For instance, California Title 24 introduced demand response requirements in the 2008 revision (Section 131(g)) that applied to retailers over 50,000 sq ft. This is expanded in the 2013 version to apply to any building or tenant improvement of over 10,000 sq ft (Section 130.1(e)). For applicable buildings, total lighting power shall be capable of being automatically reduced by a demand response (DR) signal by at least 15%. While the DR requirement has not yet been included in ASHRAE, it’s likely to be included in some future revision.
Energy codes continue to evolve toward driving more energy-efficient lighting performance, both by encouraging selection of more efficient lighting sources and by mandating the use of controls to minimize or eliminate unnecessary lighting energy consumption. As LEDs capture a greater percentage of the general lighting fixture market, energy codes will no doubt continue to adopt lower lighting power densities and mandatory control requirements that take into account the beneficial properties of LEDs, which in turn will help further increase their adoption.
Charles Knuffke is the Western vice president at WattStopper and is a member of the Illuminating Engineering Society. With more than 25 years of experience in lighting controls, he has extensive experience in code development, particularly with the California Energy Commission on California Title 24, and has given many educational presentations on energy code topics.