A/V system ground

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wch

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A 120/208v-3ph-4w A/V Panel is fed from a separately derived "isolation" T/F--
the T/F will be grounded per 250-30. A/V plans call for the A/V Panel to be grounded back to the building service equipment with a #4 AWG-Cu. Question: Is that additional #4 EGC violating NEC? / or would that just be a "supplementary" ground?
 
I think it will paralell the grounds. Not sure though, if you could isolate it from the panel cabinet to the equipment it might not.
 
Buck Parrish said:
I think it will paralell the grounds. Not sure though, if you could isolate it from the panel cabinet to the equipment it might not.
Click to expand...
Forgot to mention, the A/V Panel will have an isolated ground conductor in parallel w/
the EGC back to the dry isolation T/F. To my understanding, the grounding electrode
system for both the IG and the EGC on the T/F secondary side is starts at the isolation T/F neutral bus, and the GEC should run to structural steel (and?) local metallic water pipe.
 
Here's an AV system graphic that we were given by the AV consulting engineer. Looks similar to what you've described.

Isolated%20Ground%20connection.jpg
 
infinity said:
Here's an AV system graphic that we were given by the AV consulting engineer. Looks similar to what you've described.

Isolated%20Ground%20connection.jpg
Click to expand...
infinity:
Yes, but the A/V engr wants a separate #4 Cu from his panel (maybe the isol gnd) to
go straight to the service encl, no stops at the isol T/F; that's how I read his note.

That above DETAIL looks good but I can't figure what the open contacts in the N and IG
are for (shown below PHASE X-Y-Z).
 
wch said:
infinity:
Yes, but the A/V engr wants a separate #4 Cu from his panel (maybe the isol gnd) to
go straight to the service encl, no stops at the isol T/F; that's how I read his note.

That above DETAIL looks good but I can't figure what the open contacts in the N and IG
are for (shown below PHASE X-Y-Z).
Click to expand...


They wanted the ability to remove links for testing purposes. We didn't do it.:roll:
 
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