208V & 480V circuit sharing ground

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dorfma05

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The project in question has a simple electrical distribution system. It consists of an 800A, 120/208V, 3ph, 4W, service feeding an MDP. The MDP then feeds a number of branch circuits & a step up transformer. The transformer feeds a 277/480V panelboard.

If I have (1) 20A, 208V, 3ph branch circuit & (1) 20A, 480V, 3ph branch circuit to two pieces of adjacent equipment, can I share a #12 ground as long as I terminate it at both panelboards? The question comes up as I feel this may be a parallel ground path between the main service & separately derived transformer system.

Thanks in advance.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Pierre C Belarge said:
Bob
How does that installation comply with 300.3?(B)?
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Not Bob, but how do you envision that it does not?

I see an EGC from each originating panel being spliced at a junction point into one run with all circuit conductors in one raceway and spliced back into two where the circuit conductors part ways on the load end. The EGC is run with circuit conductors in compliance with 300.3(B) general statement. The installation also complies with 250.144.
 
Pierre C Belarge

Pierre C Belarge

Senior Member
Location
Westchester County, New York
Smart $ said:
Not Bob, but how do you envision that it does not?

I see an EGC from each originating panel being spliced at a junction point into one run with all circuit conductors in one raceway and spliced back into two where the circuit conductors part ways on the load end. The EGC is run with circuit conductors in compliance with 300.3(B) general statement. The installation also complies with 250.144.
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Without the OP stating the wiring method, I do not know how it was installed. We can state it is legal to perform, but it does not mean it was. ;)
 
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dorfma05

Member
Pierre C Belarge said:
Without the OP stating the wiring method, I do not know how it was installed. We can state it is legal to perform, but it does not mean it was. ;)
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It's going to be done in all EMT except for the portion which the ground will be shared that will be in Wiremold 2600 pancake overfloor raceway. These branch circuits are serving various millworking equipment in the middle of a warehouse.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Pierre C Belarge said:
Without the OP stating the wiring method, I do not know how it was installed. We can state it is legal to perform, but it does not mean it was. ;)
Click to expand...
That's a fair point...

I was assuming the circuits were sharing the same scheme, i.e. single raceway or cable, somewhere in between supplies and loads... and has now been confirmed. It seemed to me that anyone asking such a question is already aware of grounding requirements for different wiring methods... just that the requirements are not explicit on grounding from multiple sources.
 
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