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I have a split socket power source(upper is on a wall switched and lower is full time power). My desire is to have a reading lamp come on and off with the other lights in the room with the wall switch, which would be as simple as plugging into the top socket. HOWEVER, ADDITIONALLY, I'd like to be able to use the reading light when the wall switch is off with an inline switch which would need to be plugged into the lower socket. As a matter of fact, I can wire the 2 plugs to the lamp in the correct sequence to accomplish both desires. MY QUESTION IS how much trouble am I in, if the lamp is powered on from the lower full time socket AND the switch on the wall gets turned on as well?????

  • It partly depends on whether the two receptacles are on the same circuit. – isherwood Oct 17 '18 at 16:40
  • what are the ramifications of each possibility? – Zooka Oct 17 '18 at 16:42
  • I think there's a flaw in your logic, though. If you leave the inline switch on, you can't turn off the lamp with the wall switch. – isherwood Oct 17 '18 at 16:42
  • Code violation, mostly. You can't join hots from two sources, which could result in a 240v scenario. – isherwood Oct 17 '18 at 16:42
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    Not necessarily one source. MWBC's are on "one breaker". – Harper Oct 17 '18 at 19:43
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You will probably be better off overall to keep things simpler than the scheme that you think that you want. Mixing up the wiring could be problematic as indicated in the comments of the two parts of the duplex outlets are on separate circuits.

A better way to get the type of operation that you desire is to turn to the modern smart technologies. One example would be to look at the Lutron Caseta line of smart lighting products. With this you could setup something as follows:

  1. Replace the switch for the other lights with a Caseta smart switch.
  2. Add a Caseta plugin light controller to the always powered outlet to give smart control for the plug in desk lamp.
  3. Acquire two Caseta PICO remotes (small battery powered remotes).
  4. Either use wall mount kits to install the PICOs at a convenient wall location OR get desktop pedestals for the two PICOs.
  5. Pair the PICOs with the smart light switch and the plug in light controller to get the type of control you desire. As described in you question, you would likely pair one PICO just with the plug in light controller to give independent control of the desk lamp. Then pair the second PICO with both the smart light switch and the plug in lamp controller to achieve the ability to control both the lights and lamp from a single control point.

(Note that I have no affiliation with Lutron or Caseta products other than having fully smartized my home with these products).

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The problem is this is a "suicide cord". When either plug is plugged in, the metal prongs of the other plug are energized. (Maybe not in certain switch positions, but cold comfort to the dead.) So if a cat pulls a cord out of the wall and it falls on something conductive or flammable, you have both fire and shock risk.

There has to be no possibility of the hot wire or the neutral wire from either plug making contact with either hot or neutral of the other plug.

The only way I see to do that is using a DPDT switch, with each plug's hot and neutral on the poles of the switch and the lamp on the common. This is the same as what a generator interlock does.

If a center-off DPDT were used, that would suffice as the lamp's on/off switch, the switch positions would be on/off/auto.

Don't go "oh, neutral is harmless, I can tie that and do this with an SPDT". No. Neutral is not harmless in a variety of situations. Not least, your plugs may not be polarized, a socket could be miswired, etc.

But I think you will find this setup not have as convenient as you think.

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