Wiring a garbage disposal and dishwasher

gene_2007January 30, 2007

How is this typically done? I am starting with a gutted kitchen, so I have all options available to me.

Option 1) Run two separate lines to each and hard wire them directly by running the wire right out of the wall to the appliance. Pro- Neat and staight-forward, wire goes directly to the appliance.

Option 2) Run 14/3 to an outlet under the sink. Break the tab, add plugs and cords to the appliances and plug 'em in. Pro- I think I need to use an outlet for the disposal because I want to purchase an air switch. I believe these need to be plugged into an outlet, then the disposal plugs into that. Con- Dishwasher will need a cord/plug accessory and a hole will need to be made in the sink cabinet to plug the DW in.

Option 3) Run two seperate lines, but only hard wire the DW. Put an outlet under the sink to plug in the disposal.

My goals are - Do it safely and within code, keep under-sink wiring to a minimum, be able to use an air switch for the disposal.

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I have never seen a DW or disposal with a cord and plug, but I don't get out much, if they sell the cords then I'm sure it is a fine way to go.

One typical way is to run a 12/3 to a switch near the sink. From the switch the black circuit goes to the switch and then to the disposal, the red goes straight to the DW (or black to DW & red to disposal). Two separate 12/2 is also common, I prefer separate wires as the "loose neutral" problem can't happen that way. However it uses more copper and since there are only two multiwire neutral connections odds are you would not get a loose neutral problem, and it would be easy to find if you did.

You could run the 14/3 to the disposal outlet and then run a 14/2 from the outlet through the wall to hardwire the dishwasher. Then the dishwasher will have no plug and you will have one less wire under your sink.

    Bookmark   January 30, 2007 at 10:08PM
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In Canada the disposal must be hard wired on its own separate switched cc't. I've seen DW's both hard wired and plugged in, preferably on their own cc't.

    Bookmark   January 30, 2007 at 11:16PM
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In the USA flexible cords are allowed on both DW and D according to the NEC 422.16

I think the DW must be on a dedicated 20A circuit, which means 12/2 or 12/3. I am not quite certain of that, and I can not find it in the code. It could be that mine was required to be on a dedicated 20A circuit by the manufacturer and I am remembering things incorrectly. Check what your manufacturer says, the inspector may want to see that if you use 14/2 or 14/3.

If it was my kitchen I would user 12/2 or 12/3 regardless.

    Bookmark   January 31, 2007 at 12:35AM
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Ron Natalie

There's no US NEC requirement for either one to be on any particular circuit (dedicated, GFCI, 20A, recepatcle or hardwired). The manufacturers generally recommend the 20A dedicated for the DW's. If the appliances are not cord connected, an nearby disconect will be recommended. I like not to have to trust my hands to an airswitch or wall toggle when sticking them into the throat of the monster. I yank the cord out of the receptacle.

    Bookmark   January 31, 2007 at 9:35AM
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If local code require a separate circuit for each, you may use 14/3 (15A) or 12/3 (20A) and run that to a split receptacle under the sink. You would then run a switch loop up for the disposal, attach cord and plug to disposal and dishwasher, and plug them in. That satisfies any requirements for a disconnect for the appliance.

What I prefer is to run both on the same 20A circuit, setup as described above.

    Bookmark   January 31, 2007 at 10:36AM
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Wire both on the same 20A circuit. Hardwire the DW and put an outlet/cord and plug in for the Disposal. I do this all the time. It makes it real easy to disconnect the Disposal for servicing and removal. I also like the safety aspect.

As long as we're talking safety, I prefer to install a switch on the wall if an easily accessible locaiton is available, (even when using a pneumatic switch). If a hand gets stuck or the air switch fails, I would like a quick and easy way to turn off the Disposal.

    Bookmark   January 31, 2007 at 12:54PM
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Had my rough inspection today. I have 14/3 going to an outlet for the garbage disposal. From there, I have 14/2 that will be hard-wired to the dishwasher. Inspector said that the dishwasher will either need a plug or have a lock on the breaker. Do they make a lock for Square D QO double handle tie 15 amp breaker?

    Bookmark   February 6, 2007 at 11:05AM
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I'm use to white wires on white and black wires on black. Bare wire to ground. Well this disposall has one blue wire and one brown wire. What wire do I put the white wire to?

    Bookmark   July 9, 2011 at 6:58PM
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