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Discussion Starter · #1 ·
I am installing overhead aluminum tray in a data center. Many 1200-4000 amp 416 volt feeders. The tray turns down into switchgear where we are punching 3 inch holes and installing chase nipples. I was questioned about the need for grounding bushings. I believe they would only be needed if the nipple was in a concentric knockout or if for a service. Am I missing something ?
 

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I am installing overhead aluminum tray in a data center. Many 1200-4000 amp 416 volt feeders. The tray turns down into switchgear where we are punching 3 inch holes and installing chase nipples. I was questioned about the need for grounding bushings. I believe they would only be needed if the nipple was in a concentric knockout or if for a service. Am I missing something ?
You need to bond the tray to the nipple with a bond bushing.
 

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How do you get pass 250.96, 250.97, 250.98, 250.100 (if appliable) or 250.102(C), use plastic.
 

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Discussion Starter · #5 ·
I am bringing a separate grounding wire up from switchgear grounding bar and using a compression lug to bond the tray. My interpretation of 250.97 would be the application falls under exception #3. It is not a service so how is it different than EMT which would not require the grounding bushing?
 
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