How To Wire Dishwasher and Garbage Disposal on Same Circuit

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At this home there is a 20 amp breaker in the electrical panel that is penc il labeled as for the dishwasher and garbage disposal. At the junction box on the kitchen wall near the sink we see the 12 gauge wire feeds from the p anel. Three 14 gauge wires, hot-black/neutral-white/ground-green, are route d from this box to another junction box underneath the sink through conduit . A whip from the dishwasher is hardwired to the wires under the sink.
We want to add a GE half horsepower garbage disposal that is suppose to dra w only 4.5 amps. Can we just pull another hot 14 gauge wire for the garbage disposal and use the existing white neurtal already there for the dishwash er? Does it matter whether 14 gauge is used rather than 12 gauge wires for either device?
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wrote:

All the wires should usually be #12 BUT if you are serving a pure motor load like the disposal, you could use #14. (125% of FLA) Not so with the dish washer since it is not a pure motor load. Whether they can share the circuit would depend on the nameplate rating of the dishwasher. Take 125% of the largest load and 100% of the other one. It has to be 20 or less.
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On 12/8/2013 10:01 AM, snipped-for-privacy@aol.com wrote:

I'd consult the building inspector who is gonna approve it on that. He may frown on using less than #12 on a 20A breaker.
(125% of FLA) Not so

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Only inspectors who stopped learning the code before they got to article 430.
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On 12/8/2013 5:49 PM, snipped-for-privacy@aol.com wrote:

I was thinking that many dishwashers have a heating element that could bring a high resistive load into consideration. ^_^
TDD
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On Sun, 08 Dec 2013 19:15:46 -0600, The Daring Dufas

I mentioned that, we were talking about the wire to the disposal.
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On 12/8/2013 7:26 PM, snipped-for-privacy@aol.com wrote:

I believe I've seen them on the same circuit before but I haven't done house wiring as an electrician in years and the dishwasher here is on a separate circuit. I'd have to go look at the outdoor breaker panel to determine what size breaker and wire it is because I didn't install it. Besides, I have a bit of trouble walking and it's raining hogs and frogs outside right now. ^_^
TDD
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On 12/8/2013 8:54 PM, The Daring Dufas wrote:

One email friend in eastern TN, says it's raining hard there. Aftermath of that killer storm that passed?
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On Sun, 08 Dec 2013 13:01:43 -0500, snipped-for-privacy@aol.com wrote:

Mixing 12ga and 14ga on one branch? That sounds like a real no-no, even if you used a 15A breaker.

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On Sun, 08 Dec 2013 16:35:48 -0500, snipped-for-privacy@attt.bizz wrote:

Not illegal or even unusual. If you had a post light and a gate opener at the end of a long driveway you might want 12ga on your 15a circuit going down there, just for the voltage drop and between the opener and the light, 14 would be fine.
Is it worth doing to save a nickel on this 3' of 14. Not really but it might not be illegal.
Bear in mind there are a few jurisdictions in the US that won't let you use 14 for anything but that is a local amendment, made by idiots.
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On 12/8/2013 5:54 PM, snipped-for-privacy@aol.com wrote:

The city engineering department around here wants the breaker sized for the wire. It's possible that in the warmer temperatures we experience here in Alabamastan, the wire and breakers must be derated to deal with it to prevent nuisance tripping. I have checked the temperatures of many electrical panels with my infrared thermometer and they get quite hot at times under normal loads. Of course I'm looking for that hottest breaker which could indicate a bad connection. ^_^
TDD
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I don't see a problem using 15 amp breaker. I use 20 amp breaker feeding 10 ga. To 12 ga. Long run to garage. There can be a long term problem if things are not labeled.
Greg

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wrote:

The issue is the next guy who comes along, seeing the 12ga wire, inserts a 20A breaker. ...but I'll defer to those with a citation in their hot little hands.
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On 12/8/2013 8:57 PM, snipped-for-privacy@attt.bizz wrote:

I believe gfretwell is/was an electrical inspector and he is going by the NEC. The problem comes in when you have a city engineering department that has its own interpretation of the National Electrical Code like where I live. Anyone getting an inspection must do as the inspector demands even if you believe him/her/it to be wrong. You can sometimes pull out the code book and win an argument but unless it's an absolutely insane demand, it's best not to argue with the inspector. ^_^
TDD
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On Sun, 08 Dec 2013 21:57:40 -0500, snipped-for-privacy@attt.bizz wrote:

"The NEC does not address what an unqualified person might do". I got that straight from the NFPA on a proposed change about something similar.
I suppose I could blow everyone's mind by saying it is legal to use a 40a breaker on 14 ga wire if you are serving a 1HP single phase 120v motor with internal overload protection.
It is a common question in the inspector test.
FLA is 16a (Table 430.248) 125% of that is 20a (430.22) Table 316.16 says a 14 ga copper wire is OK for 20a in the 60c column.
The over current device can be up to 250% of FLA. 16 x 2.5 = 40a (table 430.52) if the motor has overload protection.
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On Mon, 09 Dec 2013 00:09:26 -0500, snipped-for-privacy@aol.com wrote:

How does the overload protection protect the wiring?

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On Monday, December 9, 2013 7:01:33 PM UTC-5, snipped-for-privacy@attt.bizz wrote:

The overload protection in this case is inside the motor itself. It's a common misconception among home inspectors too. Some of them see a 50A breaker going to an AC compressor and assume that it has to use the same size conductor that you would use for a 50A oven. They see a smaller conductor and flag it, though it's 100% code compliant to use a smaller conductor, within the rating of the AC unit specs.

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On Tue, 10 Dec 2013 05:58:54 -0800 (PST), " snipped-for-privacy@optonline.net"

Can you even try to read, Trader?
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On Tuesday, December 10, 2013 1:05:44 PM UTC-5, snipped-for-privacy@attt.bizz wrote:

You know, you're remarkably arrogant for someone who knows so little. You didn't even know how motor loads are sized. Gfre, who is/was an electrical inspector told you that you were wrong.
And what I just told you is correct. The overload protection is in the motor. That protects the motor and the *wiring* from overload, because the motor is the load. Capiche? Or would you like to dig your hole deeper?
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On Tue, 10 Dec 2013 10:27:05 -0800 (PST), " snipped-for-privacy@optonline.net"

You're completely illiterate, Trader.

What you told me was completely irrelevant because you CAN'T READ! Even Cracker Jax should be ashamed with you as an alum.
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