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The existing condition has a built-in banquette (bench) with hinged seats so that the interior space is accessible for storage.

bench closed

There is a wall-mounted receptacle inside the bench. Because of the hinged top, the existing receptacle is "accessible" (so no code violation, i assume), but it's not usable in a practical sense, since it's inside the bench.

I'd like to extend the circuit from the existing outlet to add one or two receptacles on the front of the bench

wiring plan

I plan on securing the wiring to the wall and the inside faces of the bench. As this is accessible for storage, I'd say the wiring would be "susceptible to damage," and therefore needs some protection.

First i have to transition from wiring in the existing junction box to wiring on the wall surface. I imagine I'll start by replacing the existing recepticle with a blank wallplate with knockout, to provide a place to start a run of conduit or MC cable.

enter image description here

MC Cable

MC cable whip

I understand if I were to use MC cable, the sheath needs to be bonded to an equipment ground. Is bonding at one end of the run sufficient, or is bonding at both ends of the run required?

If bonding at one end is sufficient, then I can use a metal old work box for my new receptacle, connect the equipment grounding conductor of the MC cable to this old work box, and I think I'm good to go, as the sheath of the MC would be bonded to equipment ground via the old work box at the end of the circuit. The starting wallplate with knockout would be grounded via the MC sheath, so all metal components are grounded.

If bonding at both ends is required, then I think I'm out of luck unless the box for the existing receptacle happens to be metal (I haven't checked, but I think it's likely to be plastic).

In the event the box at the existing receptacle is plastic, what other options do I have?

Liquid tight conduit

liquid tight whip

Would non-metal liquid-tight conduit be a suitable means of protection? Can it be used to provide protection in dry locations? I haven't found a non-metallic 1-gang cover with knockout, and the metallic cover wouldn't be grounded when secured to a plastic junction-box, so I'm not sure how I'd transition from the existing junction box to the liquid-tight conduit.

Wiremold steel raceway

I thought about a wiremold raceway to extend the circuit. I think this would be fine at the starting end, since their extension boxes include grounding screws.

wiremold extension box

But I haven't figured out how to transition from wiremold raceway into the BACK of an old work box to feed power to the new receptacles.

Questions

  1. Must MC cable sheath be bonded to ground at both ends, or only one?
  2. Would grounded MC sheath be a suitable ground for a metallic outlet cover on a non metallic box?
  3. Can non-metallic liquid-tight be used to provide protection from damage in a dry location?
  4. How could one transition wiremold raceway into the back of a junction box?
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  • I would use "Liquid-tight" just because it looks better, not that you need it.
    – DIY75
    Commented Jul 2, 2022 at 18:35
  • What cabinet wall socket will you use ?
    – DIY75
    Commented Jul 2, 2022 at 18:38
  • 1
    @knowitall I am planning on treating the face of the bench as a standard existing partition wall, so cut a hole in the bench and install an an old work box, into which I’d place a standard receptacle.
    – mac
    Commented Jul 2, 2022 at 18:56
  • I would install sockets with lids in the cabinet wall, they would look better when not used
    – DIY75
    Commented Jul 2, 2022 at 19:58
  • 1
    @Criggie if the box is empty or it's contents are almost never accessed I'd agree. If has stuff inside that's regularly taken in or out, OPs round about routing is probably better because it reduces the chance of anything getting caught on the new wires. Especially if using some sort of round cable that will have wedge shaped openings between it and the stringer. If using a rectangular channel this would be much less of a concern.
    – Dan Is Fiddling By Firelight
    Commented Jul 3, 2022 at 17:50

1 Answer 1

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I'd use the blank cover with the knockout and a 90 degree MC connector (shown below) and run the MC stapling it to the edge around the storage bench. Then terminate it in a metal old work box. Connect the ground from you MC to the ground in the old outlet box, either a grounded metal box or NM cable ground. At you new outlet box, connect your ground wire to the metal box with 10-32 grounding screw. enter image description here

Check your breaker size to determine the wire size you can run: 20 amp breaker- #12AWG, 15 amp breaker - #14AWG.

You might luck out and be able to get a short piece 8' of MC commonly known as a whip that comes with the wire and maybe connectors.

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  • 2
    I have done basically this many times sometimes with a box extension and a straight connector and sometimes with a 90 as pictured. I prefer MC as it is smaller and won’t hang things up as easily plus there is no need for liquid tight in this area.
    – Ed Beal
    Commented Jul 2, 2022 at 20:04
  • 2
    Is there a metal old work box that doesn't put sharp corners inside the cabinet, eg a stamped one? Thinking of pillows, sweaters, etc in there.
    – jay613
    Commented Jul 2, 2022 at 20:33
  • @EdBeal I actually meant the MC. Can't get use to the FMC and MC, I grew up with BX and Greenfield.
    – JACK
    Commented Jul 2, 2022 at 22:05
  • So it’s ok to ground the MC sheath at only one end of the run? (As in the case where the existing j box is plastic)
    – mac
    Commented Jul 2, 2022 at 22:45
  • 1
    @mac Yes, at this point the ground is the green wire.
    – JACK
    Commented Jul 2, 2022 at 22:53

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