sub-panel installation

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  #1  
Old 08-22-11, 08:30 AM
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sub-panel installation

I'm planning a 50 amp sub-panel installation 40 ft from the main panel. I plan on #6 copper for the three wires. What size for the safety ground is needed? I've heard conflicting info. Can it be smaller than the other three? If so, how much?

Also, I'm a little confused on the proper grounding techniques. Do I need two grounding bars in the sub-panel, keeping neutral separate from safety ground?

I assume that I do not need a main breaker in the sub-panel. Correct?

Thanks.
 
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Old 08-22-11, 09:12 AM
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The equipment ground can be #10 copper.

Since you said individual conductors (THHN) in conduit, you can do a 50A panel with #8 hots and neutral, #10 ground in 3/4" conduit. Copper #6 would be the correct size if you use a cable assembly like NM-B.

For grounding technique you need to buy an add-on ground bar kit for the panel. This mounts directly to the metal box with machine screws. The neutral bar that comes with the panel needs to have the bonding strap or screw removed prior to installation. The panel instruction sheet should say how to do it for that panel brand. When you install the circuits into this panel, the white neutrals go to the neutral bar and the bare/green grounds go to the ground bar which is affixed to the case.

The subpanel is in the same building as the main panel? Then a main breaker in the subpanel is not required.
 
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Old 08-22-11, 09:36 AM
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Thank you very much for your quick reply.

Yes, the sub is in same bldg. so no additional main brkr needed.

I'm planning on a pvc conduit run on the outside of the house w/THHN but will opt for larger wire (#6) anyway, and #10 gnd.

Yes, I will purchase a separate ground bar for the box.
 
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Old 08-22-11, 09:41 AM
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Since the conduit will be outside you will need THWN.
 
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Old 08-22-11, 02:00 PM
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I just bought the wire and it is dual rated. Thanks!
 
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Old 08-22-11, 02:17 PM
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No problem with the larger hot conductors -- it's good for up to 60A as described. If you up the ground to #8, the panel could be used for 70A.
 
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