Mike Dolt Enterprises
Mike Dolt Enterprises
User: bilwei, Location: Lufkin, Texas
Asked on: Monday, April 4, 2011 at 1:17 pm EDT
Answered on: Tuesday, May 14, 2024 at 3:44 am EDT
Question: Please see the attached pictures for this thread. Interesting....First off, our company did not do this work.Lead in info: Primary service is 12470 serving a 2500 KVA pad mount transformer. Secondary is 277-480V Y connected. Cable tray starts from the transformer, runs up an exterior wall (20') onto roof area (as seen in the pictures). It runs approximately 60' across the roof and penetrates the exterior wall into the electric room. The tray and wiring terminate into a Service Main Switchboard ('MSB'). 'MSB' has a 4000A Main Service Disconnect Breaker. There are (3) exact services as described herein this thread that follow the same routing as the first one. As you can see from the pictures the tray has been used to contain other branch circuit conductors. Is that compliant with the NEC?Please note that you will see a blank space like there is a hole in the picture. That blank space is were a Ground fault and phase to phase fault occurred. It took out those (4)Service conductors and eventually the padmounted transformer. I was there and witnessed the explosion. The owner had called me out to check on some electrical problems they were having. Duh.... I was within 2' of the location of the explosion. I spotted the smoking wire and made a mad dash to clear the roof and made it off just as the explosion occurred. It just goes to show all to expect the unexpected.
NEC Compliance
The use of the cable tray to contain other branch circuit conductors is
not compliant with the NEC.
According to NEC Article 392.10(B), cable trays shall only be used for the support of cables. They shall not be used for the support of equipment. Branch circuit conductors are considered equipment, therefore, they should not be installed in the cable tray.
Possible Hazard
Having other branch circuit conductors in the cable tray can create a hazardous situation. If a fault occurs in one of these circuits, it could damage the other conductors in the tray, leading to a widespread outage or even a fire.
Recommended Correction
Remove the branch circuit conductors from the cable tray and install them in a separate raceway or conduit that is appropriate for their intended use.
Additional Observations: The visible damage to the cable tray and conductors indicates a significant fault event. It is important to thoroughly investigate the cause of the fault to prevent similar incidents in the future. The absence of proper grounding may have contributed to the severity of the fault. Ensure that all electrical equipment and systems are properly grounded.* Regular maintenance and inspection of electrical components and systems is crucial to prevent electrical hazards and ensure safety. Flag for review