Cable Tray Containing Service Entrance Conductors and other branch circuits

Status
Not open for further replies.
B

bilwei

Member
Location
Lufkin, Texas
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.
 

Attachments

  • Picture 040.jpg
    Picture 040.jpg
    136.6 KB · Views: 7
  • Picture 039.jpg
    Picture 039.jpg
    137.5 KB · Views: 5
  • Picture 038.jpg
    Picture 038.jpg
    135.9 KB · Views: 9
  • Picture 037.jpg
    Picture 037.jpg
    139.2 KB · Views: 8
  • Picture 036.jpg
    Picture 036.jpg
    137.8 KB · Views: 9
  • Picture 035.jpg
    Picture 035.jpg
    137.6 KB · Views: 7
  • Picture 034.jpg
    Picture 034.jpg
    137.2 KB · Views: 6
  • Picture 032.jpg
    Picture 032.jpg
    133.2 KB · Views: 7
230.44 Cable Trays.
Cable tray systems shall be permitted to support service-entrance conductors. Cable trays used to support service-entrance conductors shall contain only service-entrance conductors.
Exception: Conductors, other than service-entrance conductors, shall be permitted to be installed in a cable tray with service-entrance conductors, provided a solid fixed barrier of a material compatible with the cable tray is installed to separate the service-entrance conductors from other conductors installed in the cable tray. Cable trays shall be identified with permanently affixed labels with the wording ?Service-Entrance Conductors.? The labels shall be located so as to be visible after installation and placed so that the service-entrance conductors may be readily traced through the entire length of the cable tray.
 
Hello Hockeyoligist, The plant manager didn't have a sense of humor that day. So I didn't ask for underwear replacement in my invoice.

That picture was taken recently for another unrelated project I was bidding. The incident (that happened 18 months ago) that caused the failure of the cable has not been corrected as you can see. There has been one more failure since the first time in another service feeder tray. I agree with augie47 about the code enterpretation. I am not so sure my competitors or the plant management understand that the cable tray is not usable unless the divider is installed, much less the danger they are putting themselves in by climbing in or around that tray. Plant management asked me to investigate and find our what caused the problem. My conclusion was; maintenance contractors and plant maintenance are constantly patching the holes in the bottom of the cooling towers directly over head by welding patches to cover the holes. I found a lot of welding slag and rods in the cable tray and some stuck to the outer jacket of the cable. I speculate that at some point that the hot slag or welding rod penetrated the outer jacket and wire insulation in combination with water leaking from the cooling towers and therefore the resulting catastrophic failure of the cable. I had to write a letter to local plant management and corporate because of the potential threat to life and property, because they have failed to act upon my first initial warning of the safety issues and code violations. I did so to protect myself incase the owner failed to correct the situation. My employees are not allowed on that roof without being suited up for the potential arc flash. I can't fix stupid or complacent managment.
 
Old thread gets new life. Replace SE Tray Cables

Old thread gets new life. Replace SE Tray Cables

Well guys, the owner has requested a quote to replace the damaged conductors. Please note that the existing tray cables are (3) conductor 500kcmil cu with a #1 bare equipment ground. Qty of (10) parrallel cables. Currently the #1 bare equipment ground in the Tray Cable is used as the grounded conductor. The #1 bare cu is connected to XO in the transformer and the neutral bus in the 4000 amp Main Switchboard. The Main Switchboard has a 4000 Amp breaker with GFCI protection. The transformer is a 2500 kva 12470 X 480-277 Y connected transformer.

Question: Can the #1 bare conductor in the 500 kcmil tray cable be used as the grounded conductor(neutral)?
I did not do the original installation.
 
Status
Not open for further replies.
Top