Wiring a garbage disposal and dishwasher

gene_2007

17 years ago

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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Comments (8)

guyinacoldhouse
17 years ago
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.
bigbird_1
17 years ago
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.
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Also, when a disposal is present you may not connect the dishwasher drain line to the drain line on the discharge side of the disposal. lazypup, i think i have asked before, but why is that? i know the code says not to, but what happens if you do? the reason i ask is that my kitchen plumbing was hacked together by the previous owner and the DW is attached to the drain line AFTER the trap via a stub up from teh main line. the GD is attached normally, and the DW knockout on the GD is still in place. the DW has a checkvalve mounted at the point it attaches to the drain line. i put that on, since we were having issues with the drain clogging and it would back up into the DW. this part was done under advice from a local "plumber", who i thought at the time knew what he was doing but have since learned he causes more issues than he fixes. he said nothing about the DW drain being hook up where it is. with the check valve in place, we have not had any issues with the DW in 3 years now. even when the septic tank backed up and caused the sink to clog. BTW, the previous owner used 5/8" flexible copper gas liine as the water supply lines to the faucet, with NO cut offs for the supply other than killing water to the whole house. at least i have managed to fix that part properly!
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My husband and I were just discussing this the other day, if we had it to do over again, we wouldn't. I don't really cook the kind of meals that need a lot of "disposing" and my garbage is picked up twice a week. I don't think it is worth the sometimes smelly unpleasantness. It probably is more likely to smell if you hardly ever use it, as in our case. I only got it because I replaced the one that went on the fritz after 16 years. I should have just ditched it then and could have gotten a different kind of sink but that's a whole other story. I also don't like how much room it takes up under the sink.
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DO NOT clip the tab between the screws on the side the white wire connects to. Only do that on the side the black wire attaches to (brass screws). Turn the breaker off. Add a short piece of wire to the black and white that are joined in the receptacle box and connect this to the other brass screw. You now have one brass screw/receptacle that is hot all the time and one that is switched. Remark the white wire that is connected to the black with tape to signify that it is hot, do the same for the white wire at the switch. Turn on the breaker and you should be set.
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Thanks for the reply Ron. The light switch controls my garbage disposal. So the wiring from the disposal goes in to the switch and then it used to go in to the old dishwasher (hard wired). I bought a 3 prong plug and now have it plugged in to the outlet behind the dishwasher (and it works) but the dishwasher doesn't fit any more because the plug sticks out too far. So I'm thinking I can possibly hard wire it in a again to the new dishwasher (is this even safe?) or I think I'll just buy a low profile 6" extension cord like this one http://www.sears.com/stellar-labs-6inch-extension-cord-with-flat-rotating/p-SPM11392602830?sid=IDx20110310x00001i&gclid=CLLL0JC109ACFQEOaQodpmMKXw&gclsrc=aw.ds Thoughts?
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guyinacoldhouse
17 years ago
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.
Ron Natalie
17 years ago
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.
normel
17 years ago
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.
cjelectric
17 years ago
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.
gene_2007
Original Author
17 years ago
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?
eyeim36_att_net
12 years ago
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?

Wiring a garbage disposal and dishwasher

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guyinacoldhouse

bigbird_1

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Wiring a garbage disposal and dishwasher

Comments (8)

guyinacoldhouse

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