On September 26, 2014 the U.S. Department of Energy issued a determination that ANSI/ASHRAE/IES Standard 90.1-2013 would achieve greater energy efficiency in buildings subject to the code than the 2010 version. The DOE analyses determined that the energy savings would be:
8.7% energy cost savings
8.5% source energy savings
7.6% site energy savings
As a result, all states are now required to certify that they have reviewed the provisions of their commercial building code regarding energy efficiency and, if necessary, updated their codes to meet or exceed the 2013 edition of Standard 90.1. States must submit certification of compliance by September 26, 2016 or explain why they cannot comply.
Why is this happening? The DOE is required by the Energy Conservation and Production Act (42 USC 6833) to review each new edition of ANSI/ASHRAE/IES Standard 90.1, and issue a determination as to whether the updated edition will improve energy efficiency in commercial buildings. If the determination is that the new version will improve energy efficiency, that standard becomes the new nationwide minimum requirement. States aren’t required to adopt Standard 90.1, but whatever standard they develop or adopt must be at least as stringent as Standard 90.1.
Some of the changes in the new standard are:
Lumen Power Densities (LPDs) for most building and space types are reduced by approximately 10% from the 2010 version.
More stringent requirements for lighting controls
A new table format for determining LPDs and control requirements in individual spaces
The DOE website contains additional information, including PDFs of the analyses they conducted.
Recently a designer specified 0-10V dimming for a series of LED downlights. The electrician powered the LEDs by connecting them to a nearby breaker panel. The 0-10V control signal was generated by the lighting control system. This was a simple system that should have worked with no problems. Much to everyone’s surprise the lights would dim but they wouldn’t go off! What happened?
Dimming light sources other than incandescent is a technical challenge. It requires the ballast (for fluorescent, HID, cold cathode, etc.) or the driver (for LEDs) to precisely control the amperage and the voltage, and may also require converting the incoming AC to a DC output (for some LEDs). This is difficult for fluorescent and HID lamps because the electricity must arc from one side of the lamp to the other, and at low power levels that arc simply fails. Dimming LEDs often results in a visibly jittery dimming curve as well as a jump to zero when dimming down and a jump to on when dimming up. (This article in Electrical Construction & Maintenance is a good overview of the problems with dimming LEDs.)
In architectural lighting, however, the inability to dim all the way to zero is usually not seen as a problem. Typical dimming applications such as classrooms and meeting rooms may want to dim lights for a presentation, but some light is still desirable so that attendees can see each other for discussion and see their desktop to take notes. Dimming is acceptable as long as the dimming is smooth down to a minimum light level. In these installations the drop from, say, ten percent to zero isn’t an issue because it doesn’t happen until the room is empty and the lights are turned completely off.
With 0-10V dimming, though, the dimmer or driver is powered by the incoming line voltage, so its always operating. As a result, its minimum operating capacity is also the fully dimmed state. A 100-10% ballast or driver, for example, has a minimum output of 10% not zero. When the fader is at the bottom of its travel we would normally expect the lights to go off, but they only go to 10%. Here’s a graph showing the performance of representative LED fixtures dimmed with a 0-10V dimmer.
The solution is to provide separate switching of the line voltage delivered to the fixture. Most wallbox dimmers have a toggle switch below the fader so that the fixture can be shut off at any time. Here’s a schematic of a simple circuit.
Other solutions come from other dimming techniques, including three-wire and four-wire dimming where the line voltage and the control signal come out of the same device. This guarantees that at a minimum state power to the fixture is shut off. Other control protocols, notably DMX512, and the electronics that utilize them can usually dim to zero.