grounding wires and junction boxes

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Old 04-24-07, 02:58 PM
ddr
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grounding wires and junction boxes

I just want to clarify some grounding/box fill issues regarding junction boxes. Iíll list a couple of situations and the way I think it should be grounded and the box fill. Please tell me if Iíve got the rules correct.

Say you run two EMT conduits to a metal junction box. One conduit has a 240V circuit (black/black with red tape/white/green grounding) and the other conduit has two separate circuits black/white, black/white and 1 green grounding wire running through it. There are no clamps inside the box other than locknuts.

Situation 1: The J-box acts only as a pull point; the wires pass through with no splices to two conduits on the other side. GROUNDING: The box does not need to be grounded since there are no splices in the box. BOX FILL: 9 since each wire counts once and the grounds are separate.

Situation 2: The wires and ground from the 240V circuit pass through the J-box to another conduit as above, but the wires from the other conduit are split in the J-box so that each circuit exits in its own conduit with its own ground wire. GROUNDING: The 240V grounding wire does not need to ground to the box since it passes through. The incoming grounding wire from the conduit with 2 circuits must be spliced to the grounding wires exiting to the new individual circuits and must pigtail to ground to the box. BOX FILL: 9 since the 240V ground counts as 1 and the incoming ground from the conduit with 2 circuits counts as one, but the pigtail and two outgoing grounds spliced to it are not counted.

Thanks in advance.
 
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Old 04-24-07, 03:51 PM
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here is a sticky point. you do not need to ground the box if there are no splices, but you spliced the ground from one conduit, so you must splice them all and bond the box.

that does not change the box fill.

And I get 8 for box fill. All the grounds count as one.
 
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Old 04-24-07, 08:32 PM
ddr
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jwhite: Thanks for the info. I thought that unspliced grounds counted separately and therefore counted each one.

As for the splice one, splice all situation, I'm curious as to why this is. I get that once there's a spliced ground the box needs to be grounded along with that splice, but why would an unspliced ground need to be opened up and added to the splice? Isn't this just creating a potential fault spot in a wire that was otherwise a solid run?
 
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Old 04-25-07, 04:30 AM
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You are reading the exception before the rule.

The rule is that every box must be grounded. All of the ground wires entering the box must be tied together and the box must be grounded.

The exception lets you not do this if certain criteria are met. The criteria are that there are no splices in the box. If you make a splice, you no longer meet the criteria and so you must follow the original rule.
 
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