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I am planning to pull three sets of four conductors (3 AWG wire) through 2" EMT conduit for a 30' length that is common to all three sets of wires, and then branch off at a listed metal junction box (10"x10"x4") to three 1 1/4" EMT conduits. I am doing this because I am planning to run wiring for three 100-amp subpanels from a 200-amp main.

I was not planning to make any mechanical connections inside of the junction box and just use the junction box to pull the wire through. Do I have to strip back insulation on the ground wires to make direct connections to the junction box?

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250.4(A)(2),(3), & (4) says that "Normally noncurrent-carrying conductive materials enclosing electrical conductors or equipment" should be grounded and bonded. So while you may not have to connect the equipment grounding conductor to the box, the boxes do have to be grounded and bonded. Since you're using EMT, the boxes can be grounded and bonded via the conduit. If you were using nonmetallic conduit, you'd have to ground the boxes some how.

  • Thank you, this is exactly the type of clause I thought I might be overlooking. I am using EMT for the whole run, so I should be good. Just to confirm one more thing: If I were to use a nonmetallic junction box instead with the EMT conduit, then would I have to make sure that the two sections of conduit are connected via grounding bushings and wire, or is a connection to the grounded subpanels sufficient (assuming unbroken lengths of EMT to the subpanels on either side of the junction box)? – statueuphemism Jun 2 '15 at 1:14
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    Yes, if you used nonmetallic boxes, you'd have to bond the two pieces of conduit together. – Tester101 Jun 2 '15 at 9:18
  • Neat. I had this question today, and here it is, answered! – Karl Katzke Jun 2 '15 at 17:43
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No, you do not have to attach a grounding wire directly to the metal enclosure if you are just using it as a pull point and you are otherwise grounding it using continuous runs of EMT. 250.148 from the NEC for grounding conductors to boxes only applies where conductors are spliced within a box, or terminated on equipment within or supported by a box.

From the 2011 NEC:

250.148 Continuity and Attachment of Equipment

Grounding Conductors to Boxes. Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductor(s) associated with those circuit conductors shall be connected within the box or to the box with devices suitable for the use in accordance with 250.148(A) through (E).

Exception: The equipment grounding conductor permitted in 250.146(D) shall not be required to be connected to the other equipment grounding conductors or to the box.

(A) Connections. Connections and splices shall be made in accordance with 110.14(B) except that insulation shall not be required.

(B) Grounding Continuity. The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire, or other device fed from the box does not interfere with or interrupt the grounding continuity.

(C) Metal Boxes. A connection shall be made between the one or more equipment grounding conductors and a metal box by means of a grounding screw that shall be used for no other purpose, equipment listed for grounding, or a listed grounding device.

(D) Nonmetallic Boxes. One or more equipment grounding conductors brought into a nonmetallic outlet box shall be arranged such that a connection can be made to any fitting or device in that box requiring grounding.

(E) Solder. Connections depending solely on solder shall not be used.

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    That said, it's not a terrible idea to ground the box anyway. – friedo Jun 2 '15 at 1:03

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