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I've just plumbed in a new garbage disposal unit under my sink. The plumbing appears to be fine - nothing is leaking so far.

Now I need to wire it in.

It's next to a dishwasher, but the dish-washer has a direct wire from the circuit box in the basement. I don't want a run a whole new circuit up from the basement, and I already have the romex for the dishwasher coming up, and wired into the dishwasher about 2 feet away.

What are my options for using that existing wire? Can I split it and direct wire both? Can I turn the romex into a socket, and plug both into that?

Something like this, but with a double-socket.

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What size breaker do you have for the dishwasher? And what size wire And what is the rated load on the dishwasher and disposal? –  Jay Bazuzi Feb 26 '12 at 23:42
    
@JayBazuzi - It's a 20 Amp breaker. The dishwasher specifies a 15 or 20 Amp line. Not sure about the disposer. –  Alex Feb 26 '12 at 23:55
    
Remember that all junctions must be contained in an appropriate box. The built-in box on the dishwasher may or may not be large enough to contain the amount of wires required for the junction. –  Tester101 Feb 27 '12 at 11:49
    
Or you can use an air switch to turn on the disposal. –  el katz Mar 11 '12 at 5:35
    
Yes, but I want the disposal to have to be sealed to be on. Also, my question is more about powering the unit itself, rather than how to control it. –  Alex Mar 11 '12 at 6:12

2 Answers 2

up vote 4 down vote accepted

I only have 2005 NEC handy, but there's nothing there against using same circuit for both dishwasher and disposal.

210.23(A) Branch circuits, rated 20 or 15 amperes may feed lighting units, utilization equipment or combination of both. The rating of of any one cord and plug connected utilization equipment shall not exceed 80% of the branch circuit ampere rating.

Your local code could be different, of course. Also note, that your garbage disposal needs a disconnect switch

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There is an additional clause of recent NEC codes that says that the "appliance branch circuit" (the circuit that powers the countertop outlets) of your kitchen cannot be used to power "built-in appliances" such as the dishwasher and disposer. However, the dishwasher and disposer can still be on the same branch circuit; it's just that neither of them can be on the same circuit as the one powering your toaster. –  KeithS Feb 29 '12 at 21:52

The reason why a dishwasher should have a separate circuit is because of the electrical loads. If your dishwasher is running, it will draw some power, possibly a significant amount if the water temperature is being raised inside the dishwasher. Many dishwashers will have a heater in there, because the temperature of the hot water supply is inadequate.

So if the dishwasher is running, and then you kick on the disposal, you can easily overload that circuit.

In addition to that, the outlet a disposal is on is probably a switched one, or it needs to be so, to turn that motor on and off. You don't want the power to your dishwasher being interrupted in the middle of the run. Yes, it is true that you can split most duplex outlets so that one half is switched and the other permanently on, but for the reason I gave above, it is not a good idea here.

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The disposal doesn't require a switch. –  Alex Feb 26 '12 at 15:24
    
@Alex How do you turn it on and off then? Does it have a built in sensor that tells when to turn on or something? You of course can have a switch in the sink that goes after the power to the two appliances, but a switch would still be needed. –  Kellenjb Feb 27 '12 at 13:44
    
@Kellenjb - yes, it has a sensor that activates it when you put a stopper in the hole. –  Alex Feb 27 '12 at 16:04
    
@Alex That is pretty awesome. –  Kellenjb Feb 27 '12 at 16:05
    
I have a bunch of kids, and I don't want a disposer that can run while open. I only want one that can run shut. Also, being from the UK, that's much more normal to be batch mode only. In the US the only model I know that does that is the Insinkerator Evolution Cover Control, which is the model I have. –  Alex Feb 27 '12 at 20:03

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