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switch for my garbage disposal is blowing my circuit breaker

switch for my garbage disposal is blowing my circuit breaker


Old 03-26-07, 12:14 AM
Thread Starter
Join Date: Mar 2007
Posts: 1
switch for my garbage disposal is blowing my circuit breaker

I just installed a garbage disposal in my house, and finished up the wiring, but it's having some issues. There wasn't an old disposal installed, and since the house is pretty old, I didn't have a dedicated circuit to wire the disposal to. Instead, I joined it to the circuit that the dishwasher is hooked up to.

I cut the dishwasher wiring (12-2 wiring) and spliced in the wiring for the disposal (14-2 wiring) in a j-box. I then fished this wiring up to the wallbox switch location, and then fished another wire to a wallbox under the sink. At the wall box for the switch, I connected each pair of wires with wire nuts, and then connected them to the switch. At the wallbox under the sink I ran the wire in flexible conduit to the bottom of the disposal where I made the electrical connection.

All of the connections are grounded, and as far as I can tell, I made the hot-to-hot (black to black) and neutral-to-neutral (white to white) connections everywhere along the path - HOWEVER - when I have the switch for the garbage disposal in the OFF position, and turn the circuit breaker on, the disposal starts running. If I turn the switch to the ON position (in an attempt to shut the disposal off,) the circuit breaker blows.

Do I have a short circuit somewhere? Did I mix up my wiring and polarity somewhere along the way?

Any thoughts and suggestions would be greatly appreciated.

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Old 03-26-07, 01:29 AM
Join Date: Aug 2005
Location: USA
Posts: 995
It sounds like you ran the switch in parallel with the appliance. Only the hot wire and a switched hot wire needed to be run to the switch, no neutral. The switch should be in series with the appliance, and only on the hot wire.

The hot will go first to the switch, and the switched hot wire will come back and go to the appliance. The neutral just goes straight to the appliance.
Old 03-26-07, 04:45 AM
Join Date: Oct 2006
Location: Wilmington
Posts: 4,219
You cannot mix #14 wire in a 20A circuit.
Old 03-26-07, 05:19 AM
Join Date: Mar 2005
Location: Chesapeake, VA
Posts: 340
There is clearly there is a short circuit somewhere. It sounds as though you have a switch loop wired up like a series switch. Swap the flex conduit's white wire with the switch loop's black wire in the box under the sink, and I think you'll be fixed. Actually, before you do anything- it's tough for us to tell what's going on and we may inadvertantly tell you wrong, or be misunderstood- grab a blank sheet of paper and draw a picture, the problem should be apparent.

At any rate, you're lucky that #14-2 didn't explode when you flipped the switch! Take it out and use #12-2, it's the law- #14 is only rated for 15A and can start a fire if used on a 20A circuit. You've probably damaged that switch by this point, too, I'd recommend replacing it; and given the load the garbage disposal pulls, this is definately a place to use a heavy-duty switch vice a cheapo 10A one.
Old 03-26-07, 05:29 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
You should not be attempting electrical work until you know what you are doing.

As I read it, you connected both the hot and the neutral to the switch. WRONG! And dangerous. Of course this trips the circuit breaker. You should be thankful it did. A fire might have occurred if it had not.

The white wires (the neutrals) get connected together. The black wires get connected to the switch.

However, you need 12 gage wire. Pull out what you installed and use 12-2 NM cable.

Better yet, shut off the breaker and do not use either device until you buy and read the book "Wiring Simplified" or a similar book on home wiring, and THEN fix the circuit.

Last edited by racraft; 03-26-07 at 06:42 AM.
Old 03-26-07, 07:46 AM
Join Date: Sep 2000
Location: United States
Posts: 18,497
On some projects, like building a birdhouse, it's okay to try it first and figure it out later. But with electrical projects, it's always a good idea to figure it out first, and then do it. And, unlike the birdhouse, there's very little reason to get creative in home wiring.
Old 03-26-07, 10:39 PM
Join Date: Aug 2005
Location: USA
Posts: 995
Was the #14 wire in question another NM cable, or was it part of a factory pre-wired (and UL-listed or equivilent) whip coming off of the disposal?

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