Conduit--PVC to FMC?

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Old 11-09-06, 08:07 PM
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Conduit--PVC to FMC?

I am planning a subpanel installation in a detached garage using PVC conduit to route the wire (8 gauge through 1 1/2" PVC). I've done a subpanel and plenty of other wiring within the house and passed inspection, and I have a pretty good handle on the differences with a detached structure.

My dilemma is as follows: Due to space constraints, it will be very difficult to continue using PVC after the conduit enters the house. If possible, I would like to transition from PVC to flexible metal conduit once inside the exterior wall and then run the FMC the last few feet to the main panel. Can this be done within the Code, and even if within the Code, does this present any concerns? If this won't work (or even if it will), do I have any other options?

Also, I recognize that I am oversizing the PVC conduit, but that's because my tendency is to go a little overboard in leaving flexibility for the future. The problem this presents is that, right now, I prefer not to run 1 1/2" conduit through my wall. The reason is that my house wall is stucco over two very thick terra cotta bricks, which makes drilling rather challenging. There is also the issue of buying another rather expensive masonry bit. Therefore, I am thinking of using a couple of reducers after the large conduit leave the ground, so that I am down to 1" conduit through the wall. Is there any reason this would not be workable?

Thanks.
 
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Old 11-09-06, 08:16 PM
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With conduit that big, you could pull #8 UF through it and not have to worry about conduit whatsoever once you enter either structure
 
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Old 11-10-06, 06:39 AM
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Grover, I assume the smilely at the end is because #8 UF would be a pain to pull through conduit, even if the conduit is 1 1/2". Do you happen to know if I can connect PVC to FMC?
 
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Old 11-10-06, 08:46 AM
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Yes, you can; however, with flexible conduit you are still required to have no more than 360 degree of bends between pull boxes. The 360 degrees counts all bends including offsets.

Instead of FMC, you may want to consider using ENT (a.k.a. smurf tube from its bright blue color). It is a flexible PVC conduit that can be glued directly to rigid PVC fittings.
 
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Old 11-10-06, 09:27 AM
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Ben, thanks for the feedback. FYI, I am in good shape on the conduit bends. Between the two conduit bodies that attach to the house/garage, I will have two 90s and two 45s. That means I start fresh from the house to the main panel, and I have only a few feet to travel, with at most about 120 degrees.

My limitation with smurf tube is supply. The local big boxes don't stock larger than 3/4", which makes for a tight fit with three #8s and a #10 ground. If I am stuck with 3/4" smurf tube, that would make for a lot of reducers in a short span. Of course, I may again be facing supply issues, since the big boxes only carry reducers that drop one size (i.e., 1 1/2" to 1 1/4", 1 1/4" to 1", and 1" to 3/4"). I haven't seen any that drop more significantly. Apparently that's only for plumbers.
 
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Old 11-10-06, 10:10 AM
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> using a couple of reducers after the large conduit leave
> the ground, so that I am down to 1" conduit through the
> wall. Is there any reason this would not be workable?

I think you should only reduce the conduit at pull boxes, not inline of a run. Take the 1-1/2" up to the LB fitting and use a glue-in reducing bushing to reduce the "output hole" of the LB to whatever size you want through the building wall. That should make the long run easier to pull and the conduit won't look odd reducing inline. If you can't find conduit reducing bushings, I think using a plumbing one would be okay since the electrical conduit reaches through the bushing to the LB fitting.

> local big boxes

Most electrical supply houses sell direct to the public. Check the yellow pages for "electrical supply" and call around. They should be able to set you up with the parts you need.
 
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