How do I wire a garbage disposal?

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Old 12-16-07, 08:39 AM
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Arrow How do I wire a garbage disposal?

We're going to remodel the kitchen and are planning the electric now, so I want to understand the requirements for wiring a garbage disposal.

I know it needs a wall switch, but I don't know:
  1. Does the switch location matter?
  2. Does it need a dedicated circuit like a DW does?
  3. How do I get the line from the switch into the cabinet? Can it be NMW through a hole in the sheetrock through a hole into the back of the cabinet or a rubber cord or what?
  4. Does the J box in the cabinet have any special requirements?
  5. I'm guessing it needs a GFCI?

Thanks guys!
 
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Old 12-16-07, 09:23 AM
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Easiest way is to put a switched outlet in the cabinet under the sink in the wall. You may need to pull a little sheet rock but if you cut below the cabinets it will be easy to patch. Put the switch somewhere near the sink so it is convenient to turn on when your are working at the sink. Most times we pull a 14/3 wire to the box under the sink. Switch one half (be sure to break out the tabs) for the disposal the other half is for the dishwasher. (you will put a cord on both) Then wire it in your panel with a two pole breaker. The outlet does not need GFCI protection.
 
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Old 12-16-07, 09:53 AM
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So you're saying that it's OK to have 14/3 NMW from the switch through a hole in the sheetrock behind the cabinet go through a hole in the back of the cabinet to the J box with no wire protection like conduit or whatever?

I thought the dishwasher had to be all by itself on a dedicated circuit - it can have the disposal share the circuit?

Thanks.
 
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Old 12-16-07, 11:15 AM
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With a 14/3 you are pulling 2 circuits. 2 hots and 1 neutral. You must use a 2 pole breaker. Break the little tab between the screws on the hot side (brass) of the outlet. Then pull a 14/2 up to the switch for your switch loop. Be sure to mark the white wire black of the 14/2. Half of the outlet will be for the dishwasher (ckt 1) the other half (ckt 2)will be for your disposal which will be controlled by the switch.

As far as the outlet placement, I would use a remodel box and put in the wall or if your cabinet has a back then mount it to the back. Or if you want to service mount it, then have your cables come in the back of your box. If you cant do that, then mount your J-box on the bottom and come in the bottom. Or if you don't want the J-box low then yes, you will have to sleeve the cable in some 1/2" flex or EMT to protect the cable.

As you can see, putting it in the wall will look the best and will be easier.
 
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Old 12-16-07, 12:12 PM
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We already have 10/2 in place for the dishwasher that was re-purposed from a one time 220V window A/C unit. So I guess we can't use your 2 pole breaker suggestion unless we replace the 10/2 with a run of 14/3 - which is the same work as running a new 14/2 circuit.

So, I think you indirectly answered that yes the DW and disposal each need their own circuits, right?

Also, our cabinets will have backs and yes I wouldn't want the in-cabinet box set low, so if I understand right, the 2 choices are:
  1. cut a rectangular hole in the cabinet back and plug into the wall box through the hole
  2. shield the NMW loop from wall to cabinet in a flex conduit and then add a box in the cabinet

And by "service mount" you mean a box in the cabinet?

Thank you!
 
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Old 12-16-07, 03:17 PM
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Don't run a 15 amp circuit, even a 15 amp multi-wire circuit. Run at least a 20 amp circuit.
 
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Old 12-16-07, 04:44 PM
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Originally Posted by racraft View Post
Don't run a 15 amp circuit, even a 15 amp multi-wire circuit. Run at least a 20 amp circuit.
I see people comment that running a 20 amp circuit does not cost that much more than running a 15 amp circuit but the truth is 14 ga wire is easier to work with than 12 ga. While the breakers are the same cost, the cable is almost twice the cost compared to #14. If you run #12 on a 20 amp breaker it is no safer than #14 on a 15 amp breaker. Either way you are protecting the wire and are within the Code.

syakoban - since you all ready have a circuit for your dishwasher then yes I would pull a new circuit for the disposal. If you use a remodel box and attach it on the back of your cabinet you can make the outlet look very nice and clean instead of a ragged hole cut in the back.
By surface mount I mean using a 4" steel square box and mounting it to the surface of the back of the cabinet.
 
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Old 12-16-07, 05:04 PM
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If you run a 20 amp circuit, you have room for expansion. Say you run two 20 amp circuits, one for the disposal and one for the dishwasher. Then later you want to add an instant hot water appliance. You can double up the dishwasher and disposal, and then use one of the circuits for the hot water device.

I don't know where you buy 12-2 that it twice the cost of 14-2, but you are overpaying.
 
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Old 12-16-07, 06:37 PM
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Originally Posted by racraft View Post
If you run a 20 amp circuit, you have room for expansion. Say you run two 20 amp circuits, one for the disposal and one for the dishwasher. Then later you want to add an instant hot water appliance. You can double up the dishwasher and disposal, and then use one of the circuits for the hot water device.

I don't know where you buy 12-2 that it twice the cost of 14-2, but you are overpaying.
If you think that you may want to add the hot water device (for example) in the future than by all means install the extra capacity. But if you have no need, then you are just throwing your money away.

I said "almost twice" but that was a little of an exaggeration with prices right now. This is our prices right now.

http://contractorservices.homedepot....spx?cid=851606

14/2 is about 2/3 the cost of 12/2. However about a year ago copper was WAY up and we were paying $105 for 12/2 250' at the same store. Then it was "almost" twice.
 
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Old 12-16-07, 07:01 PM
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I really like pneumatic switches for waste disposals. This does require that you have an available hole in the sink deck but it eliminates the need for a wall switch. Pneumatic switches are particularly great if there isn't wall space within a reasonable distance from the sink.
 
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Old 12-16-07, 07:28 PM
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I don't understand what a pneumatic switch is in terms of this. Can you explain?
 
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Old 12-16-07, 08:46 PM
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Take at look at this:

http://www.presair.com/home_safety_switches.asp

Be sure to look at the fact sheet.

Lowes and HD sells them.
 
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Old 12-16-07, 09:14 PM
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Interesting... do that many people get shocked using a disposal? Is there a delay when you press the button?

Any idea what they cost?

Thanks!
 
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