I found some similar questions but given possibly different base assumptions I would like just to check that what I want to do is possible with existing wiring.

In NYC, where everything is armored cable and all metal boxes are grounded I have a NEMA 6-20R outlet (in the closet) that goes to a dual breaker (labeled range, welcome to NYC). Given that every other outlet around this room is on a single breaker that’s shared with the AC :( I would love to have some plugs for vacuum, etc that won’t risk tripping the breaker if I decide to vacuum on a hot day! Is it possible to convert this outlet to standard 5-20 or even better, two of them?

Pictures of the outlet, box, breakers.

I tested the plug before turning off the breakers and it was showing 240 (120 when each side was tested against neutral) current plug

Blue wire is capped off so it’s black red and white that are connected: outlet connections

The blue wire turned out to be capped off on the panel side as well: breakers for plug wires from breakers

Can I use existing wiring and replace just receptacle and breakers (if needed)?

  • @Harper Text is clear - black, red, white (but connected to the ground pin) and blue (capped). Sep 8, 2019 at 17:57
  • So you are eliminating this outlet ? Right if so it could be done if you split a duplex receptacle this is a case where it would have to be a 20 amp one outlet on each hot, I would want to verify the ground but it looks good. If you are keeping this outlet the ground needs to be fixed.
    – Ed Beal
    Sep 8, 2019 at 18:08
  • I don’t need this outlet “as is” but I need additional separate circuit 120 outlet(s) Sep 8, 2019 at 23:19
  • Are you assuming it is 240V because of the shape of the outlet, or did you actually measure 240-ish with a voltmeter? Being NYC there is a probability that it's actually 208, which would create an additional opportunity. Sep 9, 2019 at 0:41
  • I used a cheap 120/240 meter but I do have a real voltmeter I can measure exact voltage. However, even if I can have more separate circuits it doesn’t really help - this is in the back of the bedroom closet and if I can make two separate outlets to plug a mini-fridge into one and vacuum into the other, I’m already golden. This closet it too far from the window to isolate the AC on its own circuit which would be an ultimate good but I’m not opening the walls at this point just to do that. Sep 9, 2019 at 2:09

2 Answers 2


Yes, you should be able to do this. But along the way, you need to fix the problems.

A NEMA 6-20 is supposed to be hot/hot/ground. It is NOT hot/hot/neutral. But yours is wired up as hot/hot/neutral. In the US, black & red (and blue) are hot, white is neutral. Ground is green or bare or, fortunately for you, armored cable. So the first step is:

Make this a valid 6-20

You don't actually have to do this, but if you actually wanted to use the 6-20, you would want to make it safe. Ground is not neutral.

To do that, cap the neutral (since you aren't using it) and instead connect the ground pin of the 6-20 to the metal box. That doesn't always work, but with armored cable and metal boxes that is the normal way to do things. You can get a green wire with a screw attached and screw it into the metal box.

Switch to MWBC

You can get a single 120V 20A circuit easily - just use one hot + neutral. But you can actually get two circuits. This is an MWBC - Multi-wire Branch Circuit. Each circuit gets a hot (red or black) and they share the neutral (white).

The two circuits have to be on separate poles and common shutoff - but that's already done, so this one is relatively easy. Plus everything gets grounded to the metal box. There are a few ways to proceed. The simplest that I can think of is:

  • Get a 5-20 dual receptacle. This has 2 20A 120V receptacles, which can accept plugs from any standard 15A or 20A 120V devices (like vacuum cleaners).
  • Break off the common tab on the hot side. Do NOT break off the common tab on the neutral side. Which side is which? No guarantees, varies by manufacturer/model, so check the instructions.
  • Connect red and black to the hot side - one to each screw.
  • Connect white to one of the neutral screws.
  • Connect ground with a green wire/screw to the metal box.

AFCI and/or GFCI

Depending on specific code requirements, it is likely that this circuit (120V instead of 208V/240V) now requires AFCI and/or GFCI, depending on location. The easiest way to retrofit AFCI and/or GFCI for an MWBC is to replace the double 20A breaker with a double 20A breaker that includes the necessary functions. That is different from a single 120V circuit where it is very easy to use a GFCI/receptacle combination - but those generally don't support MWBC.

  • I thought only wet area outlets needed to be GFCI? Sep 8, 2019 at 23:18
  • Depends on specific code requirements - e.g., if this is near a kitchen counter or sink then it needs GFCI. Sep 9, 2019 at 2:18
  • 1
    It’s in the back of the bedroom closet. :) welcome to NYC - this was one of those warehouse/factory conversions in the late 1970’s early 80’s. In my experience this isn’t even weird for NYC. Sep 9, 2019 at 2:19

A severe grounding mistake

The white wire is connected to the ground, which is simply wrong.

If as you say, this is AC cable, then the jacket/shield for the AC cable is a valid grounding path, meaning the boxes ground automatically when attached with a cable clamp listed for that purpose. When you have an installation where the cable or conduit provides the grounding path, it is perfectly common to see panels with no ground wires at all.

A receptacle can ground one of several ways.

  • By hard-flush contact between the yoke and the box metal (i.e. Where the screws go), provided it is flush, clean, rust-free and does not have those common paper "squares" to capture the screws. This can be via metal spacers.

  • By a self-grounding apparatus in that same location which uses springs etc. to assure hard contact.

  • Via a wire to a grounding screw on the metal box. Many boxes have holes tapped #10-32 for this purpose. Any grounding screw must be -32 or finer thread; a sheetmetal screw won't do.

  • Via a wire to a grounding clip that grabs the edge of the box.

  • One could re-task the blue wire to be ground, by removing ALL of its insulation, at all accessible points, but I would be very, very reluctant to do that. This being NYC it's possible you have 208V not 240V, and the blue wire would let you bring three 120V circuits here.

Your wiring

I note the existing wiring and configuration, noting that the white wire surely goes to a neutral bar and the black and red to a 2-pole breaker.

1 circuit

You can accomplish one circuit simply by capping off the red wire, and attaching black and white to a 120V/20A duplex receptacle.

2 circuits

You can convert to a multi-wire branch circuit for 2 full 20A circuits here, as manassehkatz describes. That will need to stay on a 2-pole breaker. (Being a GE Qline panel, we don't need to warn you about duplex breakers - they don't exist in Qline.)

3 circuits

Several things make me think you may actually have 208V here.

  • You're in New York City.
  • Someone used /4 AC cable (why on earth would they do that unless the blue wire could be useful?)
  • On this panel, look at the bottom two rows. The buses are spaced extra far apart, and the stabs come out on little extension bars screwed onto the bus. Usually they do that to make space for a third bus in the middle. Pop off that fat 20A breaker and look at the next row up. Does it have exactly the same stab arrangement as the bottom row? Or is the stab different from the bottom two, like a little "island" of its own? The latter indicates a 3-phase panel.
  • Look for 4 supply wires (3 hots + neutral) instead of 3.
  • Look for 208V between 2 hots, not 240V.

If it is a 3-phase panel, that 2-pole breaker can be replaced with a 3-pole breaker, and the blue wire can be put to good use.

You would need to either replace the junction box with a 2-gang or 3-gang, or come off the top of it with something Legrand Wiremold surface conduit starter kit, then a few inches of surface conduit over to a surface mount receptacle or two. You could fit 3 receptacles, each getting 1 hot wire and sharing the neutral, or 2 receptacles, with one split as in "2 circuits" above, and the other using the single wire.

In such a case, you must pigtail neutral, not use the receptacle as a splice for neutral.

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