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Junction Box Grounding

Junction Box Grounding

Junction Box Grounding

(OP)
I have a three core power cable and a single core ground cable, both cables are going to a motor.

I need to put a junction box for both of these cables before motor. In other words I need to put a junction box in between power supply and motor.

Now can I ground the body of the junction box with the same ground cable that is going to the motor? Or do I need to run a separate cable for grounding the body of junction box?

RE: Junction Box Grounding

It would help if you said where you were because that affects which codes apply. Perhaps I should assume that you're in the US because that's where most people who don't bother to say seem to come from, but if this was a British installation then yes you could use the cable from the supply to earth both the motor and the junction box provided you maintained the size of the earth conductor.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: Junction Box Grounding

ScottyUK
Could you please state the standard confirming the use of the earth conductor for both the purpose. Cause IEC 60364-5-54 does not specifically say that it is permitted or not.

RE: Junction Box Grounding

BS 7671 would allow it as long as the earth connection to both the motor and the junction box were adequately sized. I suspect that IEC 60364 would also permit this, although it's not a standard I use because we have a national document which takes precedence. You won't find every possible installation scenario listed in the standards: you need to be able to interpret the standard.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: Junction Box Grounding

(OP)
I am in USA. So is it permitted in NEC?

RE: Junction Box Grounding

Quote:

I am in USA. So is it permitted in NEC?

Not just permitted, required.

Metallic raceways and junction boxes must be bonded to the branch circuit grounding conductor. I'd cite the paragraphs, but I left  my code book behind.

RE: Junction Box Grounding

(OP)
If the metallic raceways and junction boxes carry phase and ground cables of a motor, then can the same ground cable (that is going to motor) be used to ground the raceway/junction-box?

RE: Junction Box Grounding

Yes. That's one of the reasons that it's called an equipment grounding conductor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Junction Box Grounding

The junction box non-carrying current metallic parts have to be grounded as per NEC Art.250.148.
Also NEC permits splicing the grounding conductor at the junction box if the connectors are listed [for ground] and well
fastened in place.
See art. 250.148 Continuity and Attachment of Equipment.
Art.430.12 says:
"(E) Equipment Grounding Connections. A means for attachment of an equipment grounding conductor termination
in accordance with 250.8 shall be provided at motor terminal housings for wire-to-wire connections or fixed terminal
connections. The means for such connections shall be permitted to be located either inside or outside the motor terminal
housing."
 

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