| Douglas County PUD, Grocery Store Electronic Ballast High Failure Rate |
Douglas County PUD is a PUD utility organization serving Douglas County Washington. One of their customers reported an extremely high failure rate of electronic ballast. The PUD ask Power Systems Engineering to investigate this problem.
The Power Systems Engineering engineer performed a power quality site survey at the store. The engineer determined that ballasts were failing because of improper and inadequate grounding of the light fixtures. Electronic ballasts were grounded via a flex conduit without a supplemental grounding conductor. The lighting circuits did not have a supplemental grounding conductor pulled in along with the phase conductors. The distribution system conduit was EMT with setscrew couplings. Many of these couplings were loose.
The engineer recommended that a supplemental grounding conductor be pulled in each lighting circuit and bonded to each fixture. He also recommended that the coupling setscrews be tightened on each lighting circuit.
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