Republication of Postings from the U.S. Department of Energy (DOE) Solid-State Lighting Program
by Jim Brodrick, SSL Program Manager, U.S. Department of Energy
You may recall that last year, DOE’s GATEWAY program released a report entitled Dimming LEDs with Phase-Cut Dimmers: The Specifier’s Process for Maximizing Success, which was created in response to issues raised about LED dimming by energy-efficiency organizations and specifiers, and was based on experience from CALiPER testing and GATEWAY demonstrations. That report was recently revised to include updated information on a GATEWAY demonstration involving the installation of LED lighting and controls at the Burden Museum in Troy, NY. The new information is very instructive.
The LED lighting — which ranged from dedicated track lighting for displays, to strip lighting in coves for uplighting the sculptural cherry-paneled ceiling, to period white globe chandeliers with A-lamps and amber rings to simulate the glow of gaslight — and controls were installed at the Burden in early 2014. Because of delays, which are quite common in architectural projects such as this one, the lighting designer rechecked the specifications. In the 18 months that had elapsed since those specifications were devised, several LED lighting products had been discontinued or redesigned, which necessitated changing the specifications and then rechecking all affected dimming zones.
In some cases, the replacement product resulted in more LED watts on the dimming zone, and this higher dimming load required a power module interface (an electrical device mounted between the dimmer and the load) to increase the dimming zone’s capacity. In other cases, the compatibility tables showed that the new LED products had a higher effective power draw (probably due to repetitive peak currents), so the load exceeded the dimmer’s capacity. Power module interfaces solved this issue as well, effectively increasing the capacity of the dimming circuit. In another case, manufacturer information showed that the changed LED product was more compatible with a forward-phase dimmer type than with a reverse-phase dimmer type, so the specification for the dimmer model was changed. The controls manufacturer worked closely with the lighting designer and the electrical engineer to ensure full compatibility on all the dimming circuits.
The specified control system was checked and ordered by a controls integrator, who worked as a subcontractor to the electrical contractor on this project. The integrator worked directly with the contractor during the installation, and commissioned the completed system to ensure that it operated as specified. Part of the integrator’s function was to keep track of design issues and changes that evolved during the project. For example, late in the project the original hard-wired control system was changed to a wireless system as that product became available, which dramatically reduced the cost of installing the wiring in the building.
Installation of the lighting and controls went smoothly, once the lighting designer made the necessary changes to the plans and specifications. The contractor was delighted that only three 20A electrical circuits were required for the entire project, and was impressed by how bright the LED lights were, given the low wattage. The controls integrator helped the contractor understand and install the control system, including the effective derating of load capacity on the control zones, and advised installing deeper switch boxes to make wiring easier, and following vertical and horizontal spacing recommendations for mounting power module interfaces between the dimmers and loads.
Museum staff members were thrilled with the visual appearance of the LED lighting, the remarkable range of dimming control, the ability to demonstrate different scenarios with one touch in a tablet or smartphone app, and the ease with which different scenes could be programmed.
The end result was that the process for checking LED product compatibility with phase-cut dimmers specified for each dimming zone worked very well. Although it added time to the design process, with a recheck and adjustments to the dimming specifications just before bidding and ordering products, none of the dimming circuits produced erratic or unexpected behavior once installed. Museum staff reported that all of the dimmable LED products dimmed smoothly to low levels.
The design costs using the LED system were higher than expected, because of redesign costs just before the project bid and also because there were multiple mockups to visually check LED luminaire performance and compatibility with the dimming system. Because the LEDs were new products to all parties on the design and construction team, nobody was familiar with the equipment, the catalog numbers, or LED installation issues. Pushing the envelope in technology can result in additional learning time and multiple iterations with luminaire and controls orders, for example, but all parties involved considered the project an invaluable experience that will reduce needed time on future LED projects.
For more details about this pioneering LED lighting project, see the full report here.
