Conduit body to main panel

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Old 11-06-15, 08:52 AM
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Conduit body to main panel


I am trying to run 2 20 amp circuits for outlets outside in pvc conduit. I have no issue with running the conduit. My question centers upon how to transition from conduit to interior wiring. I am planning to run 12 g THWN wire in the conduit and perforate the siding with a pvc LB conduit body. The only practical perforation spot is in a corner only a foot or so from the main panel in an area that is somewhat crowded with wires already. What are my options for attaching the wiring to the main panel? Do I need to connect the conduit body to a metal box using pvc close to the point where it perforates the exterior wall and run NM cable to that metal box? I'm fairly certain that I cannot make a splice in the conduit body itself (although that would be easiest) since NM cable is not technically waterproof. Maybe this is allowed? If so, I do know that the conduit body needs to have a volume stamped on it and the splices are subject to a limitation in the number depending upon the size of the LB conduit. Thoughts?

Another question regards the ground wire. I was under the impression that I only needed to run a single ground wire for both circuits (although that could be incorrect.) If so, do I connect the ground wire from both NM wires leaving the panel to the single THWN ground in the conduit? I am planning on using a GFCI breaker for both circuits.

Any help would be appreciated.
 
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Old 11-06-15, 09:26 AM
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If you're only a foot from the panel, just turn the conduit right in to the panel and keep your THWN continuous. You can use a sweep or an LB, LL, or LR fitting. Alternatively you could use a short piece of ENT (blue PVC flex conduit), which can glue directly into the PVC LB.

The conduit requires only one ground wire, matched to the largest hot conductor -- in this case #12. In the event you have multiple grounds in a box, all grounds must be connected together.

Small LBs cannot be used as junction boxes -- something like 1-1/2" or 2" is the smallest LB that is a rated junction box.
 
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Old 11-06-15, 10:25 AM
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Brilliant

ibpooks,

Thanks for the idea. I didn't know that ENT existed. I've used the liquid tight gray conduit before but this is the perfect answer. Using rigid conduit is just not an option due to multiple curves but a flexible sweep with ENT will be great and easy. You say that it can be glued directly to PVC? With PVC cement or something different? I see that there are also threaded connectors. I could probably glue a short piece of PVC and a female threaded connector after the wall perforation and attach the ENT to that. Do the snap in connectors work to attach the other end directly to the panel? Or are threaded connectors with a lock ring and bushing better?

BTW, Can you explain why a single ground is required and not multiple? I realize that they all terminate at the same point in the box and that they are not typically part of the current path but intuitively, I would assume that two circuits would require two ground wires....but certainly one is easier
 
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Old 11-06-15, 01:22 PM
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ENT is made of PVC plastic and is the same outer dimension as rigid PVC conduit. You can use the same cement and fittings to transition between rigid PVC and ENT. The snap fittings are OK too. Bushings aren't required on plastic fittings.

Grounds are always all bonded together at all accessible points. If you had two ground wires in a conduit, they would be connected at each end which effectively makes them electrically identical. The single ground wire in the pipe needs to be sized to match the largest hot wire in the pipe. For example if you had 15A, 20A and 30A circuits in a pipe, you would need only one #10 ground.
 
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