Help with re-wiring a two circuit outlet with one controlled by switch

Question

(https://i.stack.imgur.com/Y7RKV.jpg)

(https://i.stack.imgur.com/yb0Ns.jpg)

I am trying to reconnect the wires for this outlet but have run into an issue. The pictures above were taken before everything was disconnected, however the wiring in the wingnut with in the box was disconnected before a better picture could be taken.

This outlet is under the kitchen sink for the garbage disposal and dishwasher. Each has their own circuit breaker. The garbage disposal is running off a switch while the dishwasher is always hot. There is a three wire and two wire bundle running into the box.

It looks like red and white from the three wire are running into the outlet. Black from the two wire is also running into the outlet. The grounds are all wingnut it together.

What I want to verify is would it make sense in this arrangement for black from the three wire to be wingnuted to white from the two wire? This appears to be what is going on in the image, however I don’t want to connect it and risk burning out any wiring when the breakers get switched on if this would not be correct.

Answer 1

Yes, it looks like this is a switch loop type wiring arrangement. The black in the /3 cable brings "hot" from the breaker panel. It then goes to the TAGGED/MARKED white wire in the /2 cable, which is the always-hot wire going up to the disposal switch.

The switch does (or does not) connect the TAGGED/MARKED white "always-hot" wire to the disposal's "switched-hot" wire, which is the black wire. That goes to the disposal outlet.

Code now requires several things missing from this installation. Partly that is because this installation is a "multi-wire branch circuit" (MWBC), two circuit hots sharing 1 neutral.

• The white wire must be tagged/marked a color (or black) to indicate it is in use as a hot wire.
• The two circuit breakers which power the disposal and dishwasher need a handle-tie so that when you shut one off, the other also shuts off. The handle-tie must be UL listed specifically for the breakers. Finding this correct handle-tie is often hard, so we recommend simply replacing both breakers with a 2-pole breaker. Such a breaker inherently has a "handle tie" built in from the factory.

• Your situation might be grandfathered, but if not, the dishwasher needs GFCI protection. The only way to accomplish this, given your circuit layout, is a 2-pole GFCI breaker in the service panel. This will also take care of the above issue, and provide GFCI protection for the disposal as well.

• It is vitally important that this MWBC not be fed off a duplex/tandem/double-stuff breaker (2 breakers in one breaker space). People often confuse double-stuffs with 2-pole breakers, but the giveaway is that the handles are not factory tied.

If you need guidance selecting a suitable breaker for your panel, ask - we have experts on that subject! Do not just slap in any random breaker into any random panel; they may seem to fit but will arc and damage the breaker and panel.

Answer 2

It makes total sense. The black, red and white cable is your feed from the circuit breaker panel. The red wire going directly to the outlet feeds the dishwasher. Coming from the switch that operated the disposal is the black and white cable. The power has to get from the black wire in the three wire group up to the switch so it took the white wire up to the switch and the black wire back down to the outlet controlling the disposal.