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I have three 10/2 UF-B cables on an exterior wall that I'd like to route to my interior load center on the other side of the wall. I intend to bring the UF-B cables into the interior wall cavity and then into the bottom of the load center.

The photo shows the UF-B cables (please ignore the one temporarily Jerry-rigged for use with an extension cord) as well as a ground wire that is connected to an ufer ground. The conduits are used only for physical protection and encased in concrete below (the UF-B is buried without a conduit). The 1-1/4 PVC conduit is sch-80 and the 3/4 conduit for the ground is sch-40. The bottom of the interior load center is just above the abandoned telephone service conduit.

I can think of two options:

1) Install two LB conduit bodies. Optionally, I could enlarge the hole from the abandoned telephone service conduit for the three UF-B cables instead of drilling a new hole. This would require installing a 90 on the 1-1/4 conduit.

2) Install a 6x6x4 PVC junction box and connect both the 1-1/4 conduit and 3/4 conduit on the bottom side. Then install a conduit from the back of the box to the interior wall cavity.

I also believe that I should install two expansion couplings for the exterior conduits. This will shortening the 1-1/4 conduit which will be a pain because the wires are inside and the conduit is too tight against the wall to use a PVC tubing cutter.

Would you chose option 1, 2, or something else? Any advice is appreciated!

UF-B in PVC conduit

2 Answers 2

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The preferred method is enter the back, not the bottom, of the panel.

The biggest problem with an LB on the interior is that you will then need to leave the LB cover accessible forever. You won't be able to finish that wall, unless you build in a little recess or cabinet door for access to the LB(s).

Every pulling point must be accessible forever when using conduit as conduit. Sometimes conduit is just used as a convenient material to guard a cable from physical damage for a short distance e.g. up a wall; in that case the full conduit rules do not apply. Other rules require the conduit to be constructed empty and the wires pulled in.

That said, they do make tight elbows made specifically for use right at the entry to an access point. You'll see why: there'd be no way you could push or pull through them, but if the end designed for this purpose is right at an enclosure where you can get in there with a needle-nose and/or put someone there to help keep it slack so you're not dragging around the corner... then it works. They're a PitA and you can only use one in a run (not one at each end).

There are physical fill limits - with oblong "cables", and three identical ones, the true inside diameter of the conduit must be at least 273% of the widest width of the cables. This can get you on Sched 80, because the extra thickness is taken from the inside (it must fit standard fittings).

If the UF is too big for the pipe, and the other end is a junction box, the cables there can be replaced with seven THHN wires (stranded is easier to pull). Ground can be common for all 3 circuits.

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  • Thanks! I edited my question to make clear that the UF-B is direct buried and the conduits are for physical protection on the exterior wall only. With that in mind, I think you are stating that I can have bare UF-B wire in the interior wall cavity and enter the load center from a bottom knockout. Correct?
    – stmp945
    Commented May 28, 2023 at 16:42
  • @stmp945 correct. No need for all the rigmarole of the conduit wiring method when it's only a damage shield for a short distance. I believe that also lets you out of the conduit fill rules. It does not let you out of the derate rules, so you have to do a 310.15(B)(3)(a) number-crunch if you add a 4th circuit. Grounds don't count. Commented May 28, 2023 at 20:36
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The box. It will simplify the rest of the process. Ue a big enough box to put your through wall where the old phone conduit is.

If the conduit is just protection at the end of direct bury cables, dig it up, remove it, cut to length, replace and re-bury it. Ugh - encased in concrete? Without being cut to length? Poor planning, indeed. If the conduit goes all the way through the concrete and then ends with the rest of the run as direct bury, you could still dig it up and backpull.

If it's a complete conduit, those are supposed to be entirely built before wire or cable is pulled, (which prevents this sort of trouble) but you should be able to attach a pulling rope and then backpull the cables to make the cut.

You could heat-bend the conduit to something much less drastic than a 90 to line up with the existing conduit. A 5 or 10 degree offset bend (two slight bends to move the conduit sideways.) That is, if it's not already at maximum bends between pulling points.

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  • Thanks for you suggestion to use a box. I edited my question to make clear that the UF-B is direct buried and the conduits are for physical protection on the exterior wall only.
    – stmp945
    Commented May 28, 2023 at 16:49

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