Difference Between 3 wire and 4 wire Cables

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XylemMike

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Auburn, New York
I have a label on a box containing a cord. The label says "10/3 21'." The cable has a black, white and green conductors.

The customer said they ordered a 3 wire cable for 3 phase. Which, I am assuming, has a 3 wires plus a ground.

Is this correct? Does the NEC define this?


Thanks,

Mike
 
What kind of cable?

NM (Romex) 12/3 will have bare, white, black and red.

On the other hand 12/3 rubber cord will only have green, white and black.
 
What iwire said.

For most (all???) 'Building wire' type cable (NM, MC) the ground isn't counted when the cable is named, so 12-2 NM has 2 circuit conductors plus the egc.

For most (all???) 'flexible cord' type cables (SO, SOOW, etc) the ground _is_ counted when the cable is named, so 12-3 SOOW has 2 circuit conductors plus the egc.

-Jon
 
XylemMike said:
I have a label on a box containing a cord. The label says "10/3 21'." The cable has a black, white and green conductors.

The customer said they ordered a 3 wire cable for 3 phase. Which, I am assuming, has a 3 wires plus a ground.

Is this correct? Does the NEC define this?


Thanks,

Mike
Click to expand...

a 3 phase motor cord (not used in concealed locations) would have 3 CCC & a ground usually -- branch circuits thay share a neutral fed by a cable gennerally have Bk,R.Bl.W,GR
 
winnie said:
What iwire said.

For most (all???) 'Building wire' type cable (NM, MC) the ground isn't counted when the cable is named, so 12-2 NM has 2 circuit conductors plus the egc.

For most (all???) 'flexible cord' type cables (SO, SOOW, etc) the ground _is_ counted when the cable is named, so 12-3 SOOW has 2 circuit conductors plus the egc.

-Jon
Click to expand...
Just to make it perfectly clear, the designation of NM on the box or reel, as well as on the jacket itself, often will read 12-2 w/g. The w/g indicates "with ground" which is additional to the normal CCCs counted in the 12-2 or 12-3 designation.
 
mwm1752 said:
a 3 phase motor cord (not used in concealed locations) would have 3 CCC & a ground usually -- branch circuits thay share a neutral fed by a cable gennerally have Bk,R.Bl.W,GR
Click to expand...
Can you give us a part number for that cord? I have never seen a 3 conductor flexible cord that had a 4th conductor to be used as the EGC. In general if you need 3 circuit conductors and an EGC in a flexible cord, you buy a 4 conductor cord.
 
don_resqcapt19 said:
Can you give us a part number for that cord? I have never seen a 3 conductor flexible cord that had a 4th conductor to be used as the EGC. In general if you need 3 circuit conductors and an EGC in a flexible cord, you buy a 4 conductor cord.
Click to expand...

Don, I did not note the colors of the 4 wire cord just that 3 were CCC with an equipment grd. most will color the white with blue marking. I personally would used a sharpie for the entire section of free conductor.
 
XylemMike said:
I have a label on a box containing a cord. The label says "10/3 21'." The cable has a black, white and green conductors.

The customer said they ordered a 3 wire cable for 3 phase. Which, I am assuming, has a 3 wires plus a ground.

Is this correct? Does the NEC define this?


Thanks,

Mike
Click to expand...

A 10/3 "cord" is going to have a total of 3 conductors, a 10/4 "cord" is what you needed if you have a 3-phase application.
 
In NM and MC the ground is not counted. Hence 12/2 has 3 wires in it.

In SO type cables 12/2 will only have 2 wires in it.

You have to watch that when ordering. Make sure you say the words with ground if you need one.
 
I think the convention is not universal.

some people automatically seem to assume there is a ground added so a 12/2 is really a 3 conductor cord.

I have ordered 12/3 SO cord and gotten 12/3 w/ground and ordered 12/2 and gotten 2 conductors and no ground.
 
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