1

I am trying to hide some cables that power some Leds strips on my countertop and my living room lamp. This is the countertop bar that separates my kitchen from the living room. Currently, there is a normal outlet where the top outlet is connected to a dimmer switch and I have a ceiling lamp connected to it. The bottom is a regular switch where I normally plug a TV, laptop, or some portable kitchen appliance such as a blender. The current outlet, is wired with 2 different hot wires (one for the switch and the other normal current) and a shared neutral. The ground is connected to a metal screw in the outlet box.

I want to hide all these cables inside the cupboard above and turn the visible outlet in a duplex outlet to plug normal stuff (laptop, blender, TV, etc). I want to make this an AFCI outlet for safety and extend downstream to a new normal outlet that will live inside the cupboard where I will plug the led strips into the "open" hot wire and the ceiling lamp into the "switch" hot wire.

After reading around, I think that what I designed in the circuit below should work and be up to code, but I wanted to double-check. While I am here also, I wanted to confirm if I need to add grounding to my downstream outlet which will only have lamps/light strips connected to it.

Also, in case it matters, I am going to cut a hole on the other side of the outlet, which is inside a wardrobe, and lead the cables to the second outlet through the wardrobe and into the kitchen cupboard.

This was an useful read to come up with this https://www.electricaltechnology.org/2020/04/wire-afci-outlet.html

Current Cirtcuit Schema Desired Circuit Schema

How it looks in real life

enter image description here

UPDATEs:

  • I will investigate how the current grounding is done, I just saw a metal screw screwed to the enclosing box which I think is metal. It doesn't seem to lead anywhere though, not a ground wire, so unclear if that's properly grounded.
  • Looking at the breaker box as it is (without taking it out to see the cables) this is on a single switch labeled "Kitchen". No appliances are on this circuit, appliances are on separate circuits.
  • Currently the receptacles are split with only the neutral being shared, and I plan to move that downstream from the AFCI.

Thanks for the detailed answer @harper! I will look into getting a Lutron lamp socket, as I agree that the current setup is dangerous in that way.

I will look into the PWM dimmer, but according to Lutron's site the dimmer I have (Maestro Tap Switch) should be suitable for LEDs and we never have had an issue.

I've UPDATED the diagrams to reflect the wiring situation properly. I currently see a 3-wire cable that is always hot, switch hot, and neutral, and these 3 cables are wired to two standard receptacles with the hot side tab broken but only one shared neutral coming out. Is this wiring incorrect? Does it break NEC 300.3?

My plan is to then:

  • Replace Standard outlet with AFCI
  • take the outgoing AFCI cables (hot and neutral), plus switch hot to another 3-wire cable to the next box. The switched how would simply be connected with nothing in-between, from the existing cable to the new cable.
5
  • I think it should be OK as long as you break the connecting tab in the lower outlet. You say the outlet is grounded to the box—how is the box grounded?
    – Huesmann
    Nov 14, 2023 at 13:50
  • What you have is a Multi-Wire Branch Circuit (MWBC) - that's how you get one receptacle switched and one always hot in your existing box. (To prove this, turn off the breaker, pull the receptacle from the box, the cable coming in will have black/red/white/bare and the black will go to one receptacle, the red to the other (with the tab broken between them), and the white to the other side (with the tab not broken).) You cannot have a GFCI on a MWBC, and I'm willing to bet that you can't have an AFCI on a MWBC, either.
    – FreeMan
    Nov 14, 2023 at 14:52
  • @FreeMan - It could be a MWBC, but it could also just be a single pole circuit with a switched hot and always hot. To the OP: what does the circuit breaker look like for this circuit - is it a single switch, or two switches with a common handle?
    – Mark
    Nov 14, 2023 at 21:07
  • Thanks for looking into this! I replied to the questions by updating the post! @Huesmann
    – joe
    Nov 17, 2023 at 15:49
  • @Mark it's all under one switch on the circuit breaker. I updated the details
    – joe
    Nov 17, 2023 at 15:49

1 Answer 1

4

First, it's a code violation to put a dimmer on a socket. The only way this is allowed is if the socket is uniquely designed to reject normal plugs, such as this Lutron line of special sockets and plugs. (They do make a split "1 lamp 1 normal" socket.) The reason is that many loads will overheat and burst into flame if fed from a dimmer.

Anyway, 120V "triac style" dimming is a horrible, terrible, lousy, no-good way to dim low voltage LED lighting. They make PWM dimmers for low voltage LED that Actually work Properly for real. Which "AC triac dimming" has never done, not even in the incandescent age. Just supply straight DC to your lights and add a $6 PWM dimmer off Amazon. Bob's your uncle. And you can use one single DC supply for all lights, and not need 2 wall-warts.

But further...

That's not going to work because you would be violating NEC 300.3, and the AFCI won't let you do that.

An axiom of electrical wiring is that all the current which goes out one wire, must return in another wire in the same cable. You're drawn a situation where some hot runs on the upper cable, some hot runs on the lower cable, and all neutral returns on the upper cable. That's a flat-out NEC 300.3 violation, and will make some current travel in a "loop". That's fine for static-load DC but not allowed with AC, because everything inside the loop becomes the core of a transformer or an induction-motor rotor (and since it can't rotate, it will get hot).

So I don't know how the newsflash about a) dimming to a socket and b) PWM dimming being so much better will affect your plans... but yes, you will need to address the current routing.

Note that receptacles can be totally split -- there is a tab on the neutral side too, that will let you supply the lower socket's neutral from the lower cable. All grounds are tied together in all boxes.

In a configuration like this, all breakers serving that same receptacle (yoke) must be handle-tied, so that a person servicing that socket turns off all power to the socket when they do. (i.e. they plug a radio into ONE socket and turn off breakers until the radio goes silent. If you didn't tie the handles, they'd only turn off 1 breaker, and wouldn't think to plug the radio into the other socket also, because that's a "1 in a million" configuration - nobody checks that.)

3
  • Thanks for your detailed reply @harper! I Updated the diagrams to clarify how the 3 -wire cable situation is laid out and how I intended to extend it
    – joe
    Nov 17, 2023 at 15:50
  • @Joe that's better as far as 300.3 but it's still not going to work, because all the neutral is going through the AFCI, but not all of the hot. So there'll be a current imbalance and it'll trip on that. Nov 17, 2023 at 18:01
  • Gotcha thanks a lot!
    – joe
    Nov 20, 2023 at 14:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.