Fast Burning Lights

Replacing 8,400 Light Fixtures in 27 Days

The installation contractor had a big problem. As his team finished building the second massive e-commerce pick module, the customer made a warranty claim for the first module’s T-8 fluorescent lamps for burning out in less than 90 days.

This was not a minor warranty claim. Each pick module had over 4,200 light fixtures. Thinking that they had a batch of bad lamps, the contractor’s electricians changed tubes, only to discover that the new lamps would not light. Testing proved that the ballasts had failed. In less than 120 days after acceptance, 2500 lamps burned out, and over 950 ballasts failed, with more failing every day. Something was very wrong.

This costly warranty claim threatened a large loss for the contractor, $150 for labor per fixture, plus material costs for 8,400 replacement lamps and 4,200 ballasts. Our task – determine if this was a design, installation or product failure.

Instant Start and Occupancy Sensors

8,400 light fixtures draw over 470,000 watts of power, providing a strong incentive to reduce consumption cost. To conserve energy, the lighting system used high tech occupancy sensors to control the lights.

There was one problem with this approach – florescent lights don't like to be turned on and off. Every time you turn one on, the electricity erodes a little bit of the anode material in the tube. Fluorescent lamps like to stay on once turned on, as the erosion happens only when starting the lamp. If you turn on a fluorescent lamp and let it continue to burn, it can last 40,000 hours or more (4+ years of life). However, continuous burning costs more in energy than the replacement cost of a lamp, to a point. Turning the lamp on four or five times a day drops its life expectancy to 25,000 hours. The higher the frequency of the on/off cycle, the faster the lamp life diminishes.

Lamps dying in less than 90 days (2500 hours of life) indicated something extreme happening. My guess was, the lamps had to be cycling several hundred times a day. The lighting specifications gave us a clue – the starting profiles for fluorescent lamps. Modern solid-state ballasts with power transistors can be programmed with different starting profiles. Program start extends lamp life by using the smallest voltage possible to gently start the lamp. Another profile, instant start, uses higher voltage and a different lamp design to deliver high light levels in the first second. While instant start delivers full power immediately, there is a price; lamp life quickly drops when the lamp cycles on and off.

The electrical engineer specified instant start. I saw an issue right away. Lighting companies don’t honor warranty claims for T-8 instant start fluorescent lamps on occupancy sensor-controlled circuits.

It made sense. When instant start lamps begin to fail, they still draw a high amperage load through their erosion-damaged anode. The circuit design of the ballast senses that the lamp is not lighting, so it continues to send the high-voltage jolt to get the anode excited. When the eroded anode doesn't start the lamp, the control circuit continues sending the high voltage. (The ballast design supplies the high voltage for less than a second when normally functioning.) As a lamp fails, the ballasts continue to attempt to light it, stressing internal circuits until they fail. Eventually, the ballast burns out and the fixture goes dark.

Negotiating the Claim 

We carefully looked at the customer specifications and lighting requirements to see if the customer specified the instant start lamps. The specification carefully defined the occupancy sensor but did not specify the use of instant start lamps and fixtures.

After I presented my assessment to the client the same day of his initial call, he called a meeting with the electrical subcontractor. At the meeting, I presented the warranty sheets from major fluorescent fixture manufacturers, highlighting warranty restrictions for T-8 instant start fluorescent light fixtures on occupancy sensors. I presented letters I’d received from the warranty managers of each of the major suppliers describing how the ballasts self-destructed with the high cycle rates occupancy sensors created. This established the cause.

There was good news. The manufacturer of the fixtures and the ballasts on this project did not prohibit warranties for instant start lights on occupancy sensors. We did have warranty coverage to fall back on for the replacement of the materials and electrical labor. After some arm twisting, the electrical contractor agreed to underwrite part of the labor cost of the ballast and lamp replacement.

There was more good news. We did not have to replace all 8,400 ballasts, as the second module used program start ballasts. The manufacturer could not supply the total demand for the project in instant start, so they substituted program start ballasts.

Implementation

The ballast manufacturer agreed to supply 4,200 new program start ballasts and provide reimbursement for the replacement lamps and half of the labor. We worked on lead times to shorten the time the manufacturer could deliver sufficient material to the site. To speed up the swap, the installing contractor set up a fabrication team in his shop that prepped the replacement ballasts.

We had four weeks to replace 4,200 light fixtures. The end user restricted access to a maximum of six aisles at any time, insisting that the electrical teams close an aisle for no more than 30 minutes, including set up and clean up. So, we created a schedule to replace the ballasts and lamps in a live pick module running 20 hours a day.

We ran a full crew nightly in the four hours of unfettered access. Half of that crew started their day before the four-hour window, positioning materials and then working under the restrictions. The other half worked after the window, changing out ballasts and lamps under restrictions and removing materials. Aisle by aisle, electricians marched through the task. The team replaced all the ballasts and lamps in both modules in 27 days.