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In my garage I have a 4 outlet receptacle on the wall.

I would like to put a receptacle on the other side of the garage for use when doing outside work or vacuuming the car (instead of running a long extension cord).

I don't want to open up the wall and fish wire through the 14' ceiling.

I'm considering UF-B 14/2 through a conduit up and over to the other side and a plug for use when I need it; like this drawing:

enter image description here

is there any safety or code issues I am missing?

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  • Can you post photos of the existing box you want to take power from? Sep 7 at 23:57
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    @ThreePhaseEel The graphic (in the red rectangle) is what is in the wall now. To the left is what I was thinking of creating
    – Marinaio
    Sep 8 at 12:29
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    This plan is 100% a safety hazard! If you'll note, every outlet in your house/garage has a female connector surrounded by plastic. The plastic acts as an electrical insulator to protect the live wires from accidental contact. Temporary loads (lights, compressors, saws, refrigerators, etc.) all have male connectors with exposed prongs. These prongs are only exposed for moments while the plug is inserted/removed, and once removed, there is no current present to flow through a person or metal item that could touch them. (Con't...)
    – FreeMan
    Sep 8 at 17:05
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    Your plan is to reverse this and provide permanent current to exposed metal prongs. If this is unplugged (and why wouldn't it be, after all, it's just an extension cord going somewhere and I need that 4th outlet), there is now current just waiting there to zap someone! DO NOT DO THIS
    – FreeMan
    Sep 8 at 17:06
  • @FreeMan Ok. I see your point. So what is there difference with this: ebay.com/p/17014654479
    – Marinaio
    Sep 8 at 20:31
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If you're willing to accept and install surface wiring you might as well fully embrace it. Don't connect to the existing receptacle with a plug; instead add an "extension box" at that existing receptacle and run the surface conduit directly into that to make the connection permanent.

As for the proposed UF-B cable -- don't use that; it'll be unnecessarily difficult to work with. The location is dry so NM-B cable is an option (but don't use that, either). Pulling UF-B through conduit would seem impossible; pulling NM-B through conduit is still difficult, and either would require oversize conduit. Because you're going to install conduit the wiring can be even easier: use loose THHN/THWN/etc conductors. You'll be able to use 1/2" conduit and those conductors will practically pull themselves through it.

The 14/2 size is likely wrong also: if you've confirmed that the existing receptacle is truly on a 15 amp circuit then 14 gauge is OK, but circuits in a garage are often 20 amp. In that case you'll need 12 gauge conductors.

The conduit could be PVC as pictured, EMT, or a flat type designed for surface wiring. Wiremold is a brand name of one such kind of "surface raceway;" there are other brands too.

Here's a photo of a project somebody did with the Wiremold products. One of the outlets was existing and was flush to the wall surface. They've added an extension (in this case the "Wiremold surface conduit starter box") to get up onto the surface of the wall, then conduit/raceway and a surface box with another outlet. (Kevin Standlee, "New Outlet")

surface raceway outlets

If you don't like or can't easily obtain the Wiremold products something similar might be done with cast aluminum or drawn steel parts. A steel 2-gang box was easy enough to find, but I've come up empty in my search for a steel 2-gang extension box (1-gang handy box extension, 1-gang to 2-gang adapter, and 4-11/16" extension are easy to find). I'm thinking it could be achieved with a 4-square extension box with a 2-gang device ring on both sides of the extension.

weatherproof extension box

4-square extension

2-device ring for 4-square box

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  • This is a good solution and looks much more professional with very little extra cost or effort.
    – JPhi1618
    Sep 7 at 21:24
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    I think OP would benefit from instructions on how to most easily attach surface conduit to existing flush receptacle in wall. I'm not sure about this myself and it seems like the most challenging piece. The most obvious way, opening up the wall, would make the project much bigger.
    – jay613
    Sep 7 at 23:02
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    @jay613 extension box. If it's wiremold then a Surface Conduit Starter Box. Sep 8 at 0:40
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    @Marinaio The truth is I'm not entirely certain about what code has to say on the subject of attaching a cord end (the male plug) to a building cable (UF-B/NM-B), but I'm skeptical of it. I know a cord end can be installed on e.g. SO or SJ cordage, but cordage can't be used for permanent building wiring. To use UF/NM cable to cross the room and cordage for the final feet to the cord end requires some junction box at the splice point. All those questions can be avoided by ditching the plug and adding an extension box.
    – Greg Hill
    Sep 8 at 17:08
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    @FreeMan I think OP wants to build a permanently installed extension cord. The receps on the red wall on the right are the source of power; the male plug is dead until plugged into those receps. At that point the gray receps on the left side of the image become energized. I don't think OP is looking to build a "suicide cord" with an energized male plug.
    – Greg Hill
    Sep 8 at 17:10

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