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A wall has been framed out to mount a touch screen computer monitor. Once the monitor is installed it will be used as a home automation hub.

What is the proper way to supply power to this monitor? The monitor needs to be plugged in somehow to 120v electrical outlet, while also meeting NEC code.

This monitor also has a small power supply (shown below). Where should the power supply be housed? There is a cavity behind the monitor, within the wall framing, for it to sit, but that doesn't seem safe, especially when there's a label on the power supply, "Caution, my get hot".

The current plan is as follows:

Run the line cord through an electrical conduit. I would first lengthen the monitor's factory line cord by cutting off line cord's wall plug and the ac power supply plug, and then splice a SO cord to the wall plug and power supply ac plug, lengthening the line cord. At this point the line cord is around 20 feet, which would then be fished through the gray electrical conduit in the picture. At the end of the conduit is a junction box where the line cord comes out of the wall and plug into a wall outlet, which is a couple of feet away from the junction box.

If I went this route, that would mean splicing the factory monitor line cord, in order to lengthen it. And if that was done, does doing so break code if the splice is inside the gray electrical conduit?

Framed Out cavity for touch screen monitor

Electrical conduit is on the right

Monitor Power Supply

Monitor Cavity

  • What's the thickness of the monitor vs. the depth of the joist bay you're fitting this into? – ThreePhaseEel Jul 17 '16 at 0:40
  • @ThreePhaseEel The monitor is about 2.5" thick, with ~1" recess seen in the pic above. The framed out joist bay is 3" thick. – Ryan Lazuka Jul 17 '16 at 0:50
  • Is it OK if the junction box sticks out of the back of the plywood backplate? It sounds weird, but I'm having trouble finding junction boxes shallow enough for this application -- to avoid sticking out the back of the plywood, the box needs to be under 1.5" deep, and most boxes are deeper than that... – ThreePhaseEel Jul 17 '16 at 2:32
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Your current plan is no good -- first off, 400.8 point 1 forbids the use of cords as a replacement for permanent wiring (stuffing a cord down a conduit certainly counts, and is also prohibited explicitly by 400.8 point 6). Second, 400.9 prohibits the splicing of cord during installation. Third, wire splices need to be in a junction box so that they can be serviced in the future.

A better plan would be to bring the conduit out to the receptacle box where you plan to tap power, and then stuffing NM through the conduit (yes, this is OK). At the box end, you'd simply tie it into the rest of the wiring as you would ordinarily (using pigtails and wire nuts if they aren't already present there). At the monitor end, you'd attach a field-fittable IEC C13 connector directly to the NM cable and plug it into the monitor (you may need a right angle connector here -- make sure it accepts 14AWG as not all do).

Your other option is to use a recessed receptacle in a junction box mounted at the monitor end of the conduit, and plug the monitor's cord into it. This requires that the cord either be exposed completely, or the monitor be readily removable (i.e. "take a few fasteners off, remove a trim piece, and it comes out", not "oh, we have to tear into the wall to replace this") in order to apply 400.7(A) point 8. It also requires a way to get the cord to the recessed receptacle, considering you can't bury the junction box + receptacle in the wall.

Given that you are dealing with an AC adapter -- the recessed receptacle approach is the superior one (I don't believe you can get the smaller IEC connectors to fit on 14AWG anyway!). The main issue will be finding a pairing of recessed receptacle and shallow box that will fit together while accepting the PVC conduit. I'd start with a P&S P108W as that box is only 1.125" deep, leaving 0.375" for the cable and faceplate, and see what recessed receptacles work with it -- the silly folks at Leviton don't publish a dimensional drawing for the 689-W linked above, so I can't tell from here if it fits or not. (Drilling a 1/2" conduit KO in the above box should be OK btw -- the FS-type boxes that are designed to fit conduit are all too deep for this job.)

Oh, and if you do use the recessed receptacle approach, you'll probably need to finish out the monitor-alcove with some half-inch drywall back-to-back with that plywood backplate, using screws and standoffs to mount the electrical box. (Boxes that stick out from their surroundings are kosher by Code.) Of course, the only way any of this will work is if the cavity in the monitor will fit all of the cabling as well as the transformer and the J-box.

  • If anyone has a better idea of how to effectively hardwire utilization equipment equipped with power inlet connectors instead of screw terminals or such, please speak up! – ThreePhaseEel Jul 16 '16 at 22:41
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    What you suggest meets code and would be far better than splicing. – Ed Beal Jul 16 '16 at 22:45
  • Shouldn't one use a recessed outlet and a short cord to connect the display to that outlet and not put a connector on NM which would be effectively using NM as an extension cord? – Dan D. Jul 16 '16 at 23:00
  • @DanD. -- the 400.7/400.8 rules are specific to cord material (i.e. SJ/SO/SPT/...) There is nothing in the Code that I can find that prohibits a Chapter 3 wiring method from terminating in an appropriate, field-fitted plug or socket. – ThreePhaseEel Jul 16 '16 at 23:08
  • .... Though using a recessed outlet puts you in a far better place if/when you want to replace that monitor. – keshlam Jul 16 '16 at 23:19
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The receptacle has to be accessible. I would just mount a bell box or handy box on the left or right side of the alcove and feed it with NM cable through the the stud into the back of the box. Plug the monitor in there. Then the receptacle can be accessed by removing the monitor if you ever need to. As long as the monitor can be removed, even if it is a fixed mount, I wouldn't see a problem with it as long as the receptacle is not a GFCI.

Accessible (as applied to wiring methods). Capable of being removed or exposed without damaging the building structure or finish or not permanently closed in by the structure or finish of the building.

This means the building not an appliance or other piece of utilization equipment.

Good luck!

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