Big savings - Great lighting!

By Eric Strandberg LC
www.lightingdesignlab.com

A few months ago, Stephanie Seyk. Snohomish County Facilities Project Lead and Scott Gibson of PUD Energy Services, approached the LDL to help with a retrofit for their South County Local Office in Lynnwood, WA. They wanted to accomplish three things with the retrofit; lower the lighting loads in the facility, improve the lighting quality, and, related to the first two, demonstrate to their customers the good energy efficient lighting practices that they promote.

The bulk of the existing lighting for their open and closed offices was rather typical for a building of that period (1967); 112 prismatic, lensed, 2'x4' troffer fixtures (4 T-12 lamps with 2 magnetic ballasts in each). This resulted in overlighted work areas (60 to 100 footcandles) and a power density of over 5 W/ft2.

Toward meeting their goals, a T-5HO indirect pendant system was installed. The system uses 1/8th of the power (from over 68,000 kWh to 8,044 kWh), while delivering a more appropriate light level (35 to 40 footcandles). Additionally the lighting quality was improved in a number of ways. The indirect lighting provides more uniformity of light levels and less glare. The T-5 lamps have better Color Rendering (CRI) than the old T-12 lamps they replaced (from about 62 CRI to about 85). The high frequency electronic ballasts in the new fixtures, while saving energy also deliver flicker free illumination.

There were a few concerns about the new system that needed to be addressed as well. One, was that the ceiling height was only 9' and for an indirect system to perform well it should be at least about 1-½' from the ceiling, putting the fixtures only 7'6" above the floor. If they were to be installed in say, a middle school, an industrial space or a high activity area, this might have been too low. For an office space, filled with desks and partitions, and populated by adults, this mounting height should not be a problem.

Don Holdridge, manager of the South County offices said, "along with the improved efficiency in lighting the office; the modernization adds to the appearance of the space. The task lighting is available for those that need it and provides a good alternative to the global high intensity lighting we replaced. The lighting is softer and effective, the effort was worth it."

Another concern was the predicted reduction in light level (about half) and whether it would be enough. When light is uniformly distributed in a space, contrast is low, and the eye adapts more easily to light levels recommended for general office tasks. After a short adjustment period most of the staff felt that the light levels were an improvement. Fluorescent task lighting was made available for staff performing more demanding visual tasks.

A third concern for them was "pay back" or how long would it take for the retrofit to save enough energy to pay for the equipment and labor. In this case the payback was a little over 3 years, while this may seem like a long time, consider that the existing system was in place for almost 40 years. All of the above made for a very successful project. Excellent quality lighting was provided for about 0.65W/ft2.

Before: Before the retrofit. For nearly 40 years, 4- lamp recessed troffers using T-12 lamps and magnetic ballasts lighting these Snohomish PUD offices. Light levels in the offices ranged from 60 to 100 footcandles with a connected load of 5 W/ft2

After: After the retrofit. Indirect T5HO pendant luminaires provide much more uniform illumination at a light level around 30 - 40 footcandles. Energy usage is reduced to 1/8 the previous level. Color quality is greatly improved and flicker from the magnetic ballasts is eliminated.

Snohomish Public Utility District Commercial Incentive Programs If you own or manage a commercial, industrial, school, nonprofit, or governmental building in Snohomish County, you may be eligible for incentive funds. These funds provide reimbursement of up to 70 percent of the project cost for installing energy- efficiency measures in your facility. Examples of Measures Funded:

• Lighting Controls & Fixtures
• HVAC Equipment including Chillers & Controls
• Compressed Air Systems
• Motors, Pumps & Fans
• Refrigeration
• Heat Recovery Systems & Controls
• Variable Frequency Drives

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