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I would like to bring up 12/2 cable to put a 110 20A electrical outlet on the wall. The house is old and there is not enough space behind the drywall to put a box (it is an outside wall and there are not any outlets in it). In addition, I tried elsewhere on this wall to drill a hole down to the floor below but was unable to get it. So, I'd like to bring up a cable from the floor in front of the wall and install a surface mount box with an outlet. How should I go about this? BX cable? Conduit between floor and box?

The outlet will be for a portable air conditioning unit in the summer and space heater in the winter, thus the sole outlet on the circuit.

Red marking is where I'd like to bring up the cable and install the outlet. enter image description here

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  • How do you plan to make the junction to the existing wiring below the floor? What wiring method is used down there?
    – ThreePhaseEel
    Sep 13, 2018 at 1:46
  • @ThreePhaseEel Either a run all the way to the service panel or, if it is BX, a run to a box where I'd then use Romex. I have part of the ceiling open below it.
    – Michael C
    Sep 13, 2018 at 9:28
  • Have you though about a floor plug and plate?
    – Retired Master Electrician
    Sep 13, 2018 at 12:47
  • @RetiredMasterElectrician Thanks for this. I have thought about it, but am concerned about the door that swings near it (you can see the door on the right of the photo). I'd have to check the path of the door swing. The other disadvantage is that floor boxes here (Canada) are pretty expensive, more than $100.
    – Michael C
    Sep 13, 2018 at 13:13
  • looks like someone had a similar solution with the pipes next to your new hole.
    – Rob Elliott
    Sep 13, 2018 at 14:11

2 Answers 2

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I would use conduit for the run up from the floor

I would run a piece of EMT conduit myself, with a surface mount "handy box" to house the receptacle and a metal old work box with the conduit extending out a KO in its back for holding the junction between the 12AWG stranded THHNs in the conduit and the solid wires of the 12/2 NM-B that is the homerun for this circuit. You'll need a strain-relief cable-clamp in the KO the NM enters the old work box at; inside the box, it's a simple matter of hot to hot, neutral to neutral, and ground to the box ground screw. The receptacle wires up normally (hot to brass, neutral to silver), save for being grounded via its yoke instead of a ground wire as it's in a metal box attached to grounded metal conduit. Drywall anchors can be used for mounting the conduit straps and handy box in this case, by the way.

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  • This exactly, and I'd tuck it behind the other pipe for physical protection and less visual disruption. Note the heat of the pipe in operation, you might need to do a thermal derate on the THHN wire.
    – Harper - Reinstate Monica
    Sep 13, 2018 at 20:21
  • Just to make sure I understand this: Old work box holding the transition would sit on the floor. NM would come up through hole in the floor into KO on the floor side of this box. This KO would have a strain relief cable clamp. Transition to THHN (actually, I can only find RW90 in Canada unless I want to buy a 300M spool) inside the box. On the other end of the box is the conduit which terminates a a handy box. Receptacle goes into handy box. Is that right?
    – Michael C
    Sep 13, 2018 at 20:23
  • @MichaelC old work box sits in the ceiling below, but you are otherwise basically right -- RW90 works just as well as THHN here as long as you're within fill on the conduits
    – ThreePhaseEel
    Sep 13, 2018 at 20:43
  • I actually don't have direct access to the ceiling below, I have to fish the wire from about 15 feet away through the space between the ceiling on the first floor and the subfloor on the second floor. That said, I could mount the old work box in the floor, or have a surface mount box that sits on the floor.
    – Michael C
    Sep 13, 2018 at 20:51
  • @MichaelC -- what blocks your access to the ceiling below?
    – ThreePhaseEel
    Sep 13, 2018 at 20:59
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A common approach to wiring in habitable space rather than in a wall or ceiling is the use of surface raceways.

raceway

They are used with properly gauged and colored solid or stranded wires, rather than cable. They are terminated in special surface receptacle boxes.

raceway box

If you go this route, you also will need a transition box where the cable meets the raceway in the space below. Remember that no splices can be made outside of approved boxes or fixtures, and that any box or fixture needs to be readily accessible (not buried in a wall or ceiling).

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  • 1
    Yeah -- I briefly considered surface raceways -- but 1) trying to make the NM-to-surface-raceway transition in the ceiling below wouldn't work well (surface raceway starter boxes aren't designed to have raceways coming out their backsides), and 2) the raceway would have to be bent back to stay against the wall surface or channeled through the entirety of the baseboard (not just the quarter round)
    – ThreePhaseEel
    Sep 13, 2018 at 19:59
  • Thanks @bib I've actually used these extensively but in this case, it won't work. The problem is coming out of the floor.... there exists surface raceway system pieces for coming out of ceilings, but not floors.
    – Michael C
    Sep 13, 2018 at 21:03
  • @ThreePhaseEel Yeah, the key is where he is transitioning from, and that is not clear and may make this not work. He would need to continue the raceway system until he met a workable transition.
    – bib
    Sep 13, 2018 at 22:19

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