I recently purchased a generator that has both a 30A and 50A outlets. In order to provide my home with more amperage I decided 50A would be the better choice to install the inlet. I was lucky enough to have someone who had some 6/3 UF-B cable left over from a job and will use it for the cable run. I installed a short conduit outside my home from the basement to the garage, approx 7ft total. I used a 1.5in 40 sched pvc to have extra room to possibly run another cable in the future for an EV charger (NEMA 14-50). I know UF-B is tough to pull but since it's only 7ft with multiple access points, I was wondering if it could be possible to pull both cables.. if not then would it be feasible to place a junction box at the entry of the conduit, pulling 6AWG THWN OR THHN wiring through the conduit and then splicing them in the box?

  • I take it the conduit has LBs at each end to bring it back inside the house? Oct 8, 2020 at 11:47
  • yes... there are 2 LBs in the short run.
    – Al Leonard
    Oct 8, 2020 at 14:53
  • What were you planning to use for a generator inlet box BTW? Oct 9, 2020 at 1:38
  • 1
    Using a Conntek 50amp 125/250v 4 wire locking inlet box
    – Al Leonard
    Oct 9, 2020 at 4:24

1 Answer 1


UF-B in conduit is a nightmare.

You can't fit even one 6/3 UF-B into a 1-1/2" conduit.

One 6/3 UF cable requires 2" conduit.
Two 6/3 UF cables require 3-1/2" conduit!

Since 3-1/2" conduit is required, 1-1/2" conduit is right out :)

Your only option is to have a junction box at each end of the conduit run, and splice from UF to THHN wire for the run inside the conduit. Note that your junction box will require 65 cubic inches because you'll have 12 active conductors being spliced all in all, plus 4 grounds (which count as 1/4 wire, rounding up). Each #6 wire requires 5 cubic inches. Eight THHN wires will fit very comfortably inside a 1-1/2" conduit.

Note with #6 THHN, neutral must be on a white or gray wire, and ground must be green or bare - no remarking wires with tape.

  • One problem I could see is that they may have trouble finding suitable JBs -- this is a case where their conduit is rather fat for what they want to do, and a skinnier conduit would actually have been more apropos gasp Oct 9, 2020 at 3:15
  • Unfortunately I already have the 1-1/2 in conduit in place with a 6 x 6 x 4in pvc JB attached at one end. I intend on attaching another JB of the same size in the basement. Would that size suffice for the splices?
    – Al Leonard
    Oct 9, 2020 at 4:48
  • 1
    6x6x4 is 144 cubic inches and you only need 65, so it's plenty big enough.
    – Jasen
    Oct 9, 2020 at 11:24
  • Great.. thank you all for the assistance..
    – Al Leonard
    Oct 10, 2020 at 5:32

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