Only use 2 wires on 3 Wire Cable?????

billa_2009

15 years ago

Turned off power a breaker and pulled out dishwasher. Found 10AWG NM with 3 conductors coming straight through the wall from the panel. The red wire was cut short and not exposed. I don't know if the red wire was setup at the panel to be energized.

I only need 2 wire 12AWG for the new dishwasher.

Can I keep the current 10AWG cable?

Should the red wire be going into the ground at the panel?

Would it be better to put a junction behind the dishwasher and have the 12AWG 2-conductor come out?

Sort by:Oldest

Comments (7)

azlighting
15 years ago
what voltage and phase does the manufacturer recommend?
gblentz
15 years ago
>Can I keep the current 10AWG cable?

Oversizing wiring is fine, as long as the device it terminates at is designed to handle it.

>Should the red wire be going into the ground at the panel?

NO! Only green and bare wire are permitted as grounding conductors. Only white and gray are permitted as neutrals.

>Would it be better to put a junction behind the dishwasher and have the 12AWG 2-conductor come out?

As long as the dishwasher is permanent and the cable is protected against physical damage, I wouldn't worry about it. As for the red wire, I had this same issue and my AHJ had no problem with me "abandoning it in-place." Make sure the red wire is not connected at the panel, and cut it short. Alternatively, you could also just label the red wire "for future use" and wire-nut both ends, IIRC.
Related Discussions
Using 3 wires on a 4 wire cable?
Q
Comments (3)
I don't know if it's permissible (and I don't think it looks as nice) but when wiring lv alarm wiring, we often cut off unused wires flush with the outer insulation. You will also see alarm, telephone and other lv wires with spares wrapped back around up the outer insulation. In 120/240 land, I'm sure capping is preferred. If one of the other conductors fails in the future, the 'spare' wire can be brought into service provided it's re-coloured at the ends to depict what it's doing, ie, red or black.
...See More
Run 12/3 but only use 2 wires?
Q
Comments (1)
yes
...See More
Need help Replacing old dimmer that used only 2 wires in a three way
Q
Comments (4)
It is usually best to use a meter to test which wires do what, otherwise, you may be going back to the store to get another dimmer. There are several ways to wire a 3-way, so there is a chance that you can't tell by looking. It sounds like yours are wired like this diagram. The different color terminal is called the "common". The other two matching colored terminals are the travelers. Notice that the two traveler wires come out of the same cable, and the common comes out of a different cable. As long as you get the "common" in the correct place, the other two travelers are interchangable regardless of color. One traveler should be a red wire and the other one a black wire. The common should be a black wire.
...See More
wiring ceiling fan w/light to 2 light switches using two 2 cond. wires
Q
Comments (2)
I'm assuming both switches are on the same circuit and in the same box? Then at the ceiling box, combine the 2 white wires together with the white from the ceiling fan/light and connect one black to the fan and one black to the light. Connect all ground wires.
...See More
joed
15 years ago
Don't cut it short in the panel. Just disconnect it and leave it. You might need it some time in the future, possibly for a garbage disposal.
billa_2009
Original Author
15 years ago
All good replies.

azlighting: I don't have the new dishwasher yet but the instructions I downloaded just say 120 Volt AC and the need for black, white and ground wire in 12AWG. The dishwasher I pulled out worked without the red wire.

gblentz: OK, less work for me. I'll make sure it is capped at the panel.

joed: Good thinking on not cutting the red wire short. I'll have to look at the panel to see what they did. I didn't want to shut power down to the house until I had a plan of action and now I have one.

One more thing to all:
Whoever pulled the cable through just smashed the wallboard with a hammer and left a hole exposing the studs, insulation and exterior house sheathing. As I already have a problem with cold drafts through that wall, I wanted to close-up the hole and just have the cable come through. Would it make sense to place a junction box flush with the wall and have the cable pass through it uncut? I have a box and faceplate with knockout I can use.
jmvd20
15 years ago
You could place a box there so long as it does not interfere with the dishwasher being pushed back against the wall. You would also need to make sure you use the correct fittings to install the cable in a metal box.

Personally, I would recommend that you get a plastic remodel box and cut that into the wall (very easy to do). Then you would be able to install an outlet in the wall and use a 3 wire cord from the dishwasher to the outlet. I have never cared for romex coming out of a wall and wired directly to a dishwasher.

As far as sealing up the hole just put some insulation in the hole around where the wire comes out. That should stop the drafts from coming through.
pjb999
15 years ago
I am baffled by the practice of hard-wired dishwashers as I've seen in North America. When I lived in Australia and NZ (both 240v/50hz) all dishwashers came terminated with a suitable flex cord and plug, and electrician would supply a suitable outlet at the rear of the dishwasher spot. Seems safer and easier for repair/replacement etc.

Presumably dws here are 120v? If they were 240 I'd understand.

JMVD, are you suggesting flex from the jb to the dw? Makes sense to me, since in theory NM/Romex etc isn't really supposed to be exposed, is it? I guess when it's tucked behind the dw it's not 'exposed' per se.
gblentz
15 years ago
>Whoever pulled the cable through just smashed the wallboard with a hammer and left a hole exposing the studs, insulation and exterior house sheathing.

Don't you just love quality workmanship?

OK, depending on what zone you're in, this may raise the issue of moisture migration into, and condensation inside, the wall cavity during winter months (think mold, rot, crumbling drywall, etc.). I know there are products to mitigate this for electrical boxes, but I have no experience with them.

jmvd20 and pjb999 make valid points suggesting installing a receptacle in the wall, and a cord on the dishwasher to run to it. That's how I did ours. In fact, IIRC, there are more stringent NEC requirements for hard-wiring a permanent dishwasher compared to it being "portable" which, in the eyes of The Code, it would be if it could simply be unplugged. If you do decide to go this route, just be careful. Most (all?) 15 and 20-amp residential switches and receptacles accept #12 and #14 only. You will likely need to splice in short #12 whips to go between the #10 wires and the receptacle.