Disposal and Dishwasher Wiring Question


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Old 03-23-15, 07:10 AM
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Disposal and Dishwasher Wiring Question

Hello,
As part of a kitchen refresh, I'd like to replace my standard switched disposal with an air switch, which will plug into a non-switched outlet under the sink. Currently there is a switched outlet under the sink for the disposal, and a separate outlet for the DW (behind the DW).

The current wiring looks as follows: a 12/3 cable is coming into the switch that controls the disposal. There are 2 12-2 cables exiting the switch box. One is feeding a 20-amp single (round) outlet under the sink, which the disposal plugs into. The second 12-2 cable feeds a 20-amp single (round) outlet that the dishwasher plugs into. The circuit ends here. The DW and the disposal are on the same 20 amp circuit in the panel.

I'm not sure why there is a 12-3 cable coming into the switch, and I am not sure what to do with the red wire in the new wiring scheme.

I want a 20-amp outlet behind the DW, and a non-switched 20-amp outlet under the sink that the air switch plugs into.

Can I simply cap the red wire coming in from the power source and wire the 2 outlets as I would any other outlets, or am I missing something?

Thank you...Trish
 
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Old 03-23-15, 07:45 AM
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If the red wire is unused now just cap it and use it for future ,sounds like you want to abandon the switch for the disposal,if so just splice the wires from the switch through and remove the switch, the outlet will be live all the time that way.
Or just leave the switch on all the time,your choice.
Geo
 
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Old 03-23-15, 08:39 AM
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OK, so I may need to correct my original post.

In my panel, the Disposal is on circuit 12B, and the DW is just below it on circuit 14A. These two slim 20 amp circuits toggle together by virtue of a metal tie bar. Only one 12-3 wire is feeding these two appliances, so I presume we are looking at what you pros call a Multiwire Branch Circuit. Correct? If so, could someone describe the wiring diagram for me, starting with the
12-3 power source that will first feed the non-switched outlet for the disposal; then over to the outlet for the dishwasher.

Thanks, Trish
 
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Old 03-23-15, 08:56 AM
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You are correct about the Multi wire branch circuit, you have 2 circuits in that box Black and White 1,circuit and Red to the same white the second circuit or what is called a shared neutral.is that Red wire connected to one of the 12-2's or is it capped off? Normally that 3 wire setup would be one each for the DW and Disposal.
Geo
 
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Old 03-23-15, 10:27 AM
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These multi-wire circuits are common for DW and Disposer.
It allows each to have it's own circuit using only one 12/3 cable from panel.

The neutral is shared, you have two hot wires, each from a separate breaker.

IF the red is not being used (capped off), it is a waste of a dedicated circuit and someone along the line either didn't understand the wiring or thought it wasn't necessary. Use it now.

- The white neutral from 12/3 will be connected to whites to disposer and DW

- The red hot from 12/3 will be connected to either the black to disposer or black to DW

- The black hot from 12/3 will be connected to either the black to disposer or black to DW

You can see the black and red hot wires are interchangeable as far as which receptacle they feed, either way will work, whatever is more convenient.

Be careful working in switch box. Often times there are two switches in box, one for disposer and one for sink overhead light. The sink light will probably be on a separate 15amp lighting circuit. If this is the case, shut lighting breaker off also while working in box.

This leaves you with an abandoned switch. Post back for options on that.
 
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Old 03-23-15, 04:38 PM
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Handyone, thanks for the reply. I have demo'd the wall that contained this wiring, but was careful to label the incoming wires and the old j-boxes. The old wiring scheme was as follows: The red from the 12-3 cable and the black from the disposal 12-2 were wired to the switch. All the whites were ganged with a pigtail to the switch; same for the ground. The black from the 12-3 and the dishwasher 12-2 were ganged.

The outlets for the dishwasher and disposal were typical, with a black, white, and ground.

I understand your wiring instructions and that is how I will proceed. There was no light over the sink, and the other lights in the kitchen are indeed on a separate circuit. (There will be some lights over the sink by the time I'm done).

Thank you very much for the advice.

Regards, Trish
 
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Old 03-23-15, 04:50 PM
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Sounds like you have it well in hand.

You are just bypassing the switch by connecting red directly to black going to disposer.

The white bundle -- The only way it would have been pigtailed to old switch is if the old switch was illuminated and required a neutral.

Since the wall is open, I would move DW receptacle from behind unit into sink base cabinet.
 
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Old 03-23-15, 07:06 PM
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The switch was not illuminated....it did have a neutral pigtail...Was this unwise, or just unnecessary?

Just to clarify on the neutrals . I'll be installing the outlets in separate boxes. The first box/outlet will have 12-3 in and 12-2 out; the second box/outlet will have 12-2 in and be end of the run.
For the first outlet, I will be bundling the 2 neutrals and pigtailing a neutral to the screw on the receptacle--correct?
thanks again
 
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Old 03-23-15, 08:34 PM
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Correct.

12/3 comes into first receptacle box. This is where "split" occurs.
Neutrals bundled together with a single pigtail to receptacle.
One of the hots attached to receptacle side terminal, the other hot wire attached to outgoing power.

I won't get into why a white wire may have been attached to switch, you have eliminated that wiring, correct?
 
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Old 03-24-15, 02:45 AM
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Correct--switch is gone. And thank you again.
 
 

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