3 way wiring by code
- Thread starter EEC
- Start date
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mdshunk
Senior Member
- Location
- Right here.
Anything but green.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Make sure you tape the white wire another color and don't use that wire as the return to the light. Art. 200.7 (C)
stickboy1375
Senior Member
- Location
- Litchfield, CT
I don't use tape, I normally drill a hole in a sharpie tip and insert the wire thru the hole in the sharpie to re identify it...
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Don't forget to do your box fill calculations.
brantmacga
Señor Member
- Location
- Georgia
- Occupation
- Former Child
EEC said:
down here we're required to have a separate grounding conductor in all mc cable no matter what type of connector is used AND we have to pigtail one to the box and one to the device (yep). check w/ your local inspector to make sure they allow it. typically i'd just use 4 wire w/ the blacks being common and red & white as travelers.
The jacket on MC is not a suitable EGC (330.108/250.118(10)) unless listed and identified as such....a "new variant" (MC-AP) meets this requirement.brantmacga said:
The connector is not relevant as the jacket on the older type is not listed as EGC.
brantmacga said:
Isn't that SOP?
404.9 (A) & (B)
4-wire?brantmacga said:
12(14)/3 MC will have Black-Red-White conductors in addition to the green EGC.
What are you doing with the fourth wire?
wbalsam1
Senior Member
- Location
- Upper Jay, NY
EEC said:
Here's a wiring scheme..........
View attachment 508
View attachment 509
Actually, I think this is a code violation. I would use the white conductor (and would identify as black) at the j-box to feed the 1st switch so that I eventually returned with the black wire to the fixture.
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chevyx92
Senior Member
- Location
- VA BCH, VA
Are you serious? How effective is that? What do you have a sharpie for each size wire 14, 12 ,10 etc...stickboy1375 said:
brantmacga
Señor Member
- Location
- Georgia
- Occupation
- Former Child
he asked about color using three wire, so i assumed he was talking about black white and green. snap-tite connectors are listed for using the sheathing as EGC. 404.9 -- i use metal boxes, therefore metal device screws provide the ground.
celtic said:
B/W/Gr MC is 2 wire.....brantmacga said:
same as for Romex ~ ##/2 consists of BW and a bare EGC....
same for type AC (BX) ~ ##/2 B/W #16(?) bonding strap.
brantmacga said:
But only IF the sheath is listed as an EGC...and that will depend on the wiring type used ~ MC or MC-AP.
wbalsam1
Senior Member
- Location
- Upper Jay, NY
chevyx92 said:
"Hey Joe, toss me the #12 Sharpie, huh, I gotta dip these wires!" :grin:
"Can't, all I got's is the #14. You'll have to ram 'er in, Bud!" :grin:
brantmacga
Señor Member
- Location
- Georgia
- Occupation
- Former Child
celtic said:
Page 175, article 330 "type MC" - III Construction Specs - 330.108 Equipment Grounding, "Where type MC cable is used for equipment grounding, it shall comply with 250.118(10) and 250.122.
Page 111 - 250.118(10) says the metallic sheath of MC cable may be used for EGC.
250.122 is grounding conductor sizing.
330.24 mentions a smooth-sheath and an interlocked corrugated type sheath. i've never seen smooth sheath MC cable, so is the corrugated type the AP you're talking about?
___________________________
Quote:
Originally Posted by brantmacga
he asked about color using three wire, so i assumed he was talking about black white and green.
B/W/Gr MC is 2 wire.....
same as for Romex ~ ##/2 consists of BW and a bare EGC....
same for type AC (BX) ~ ##/2 B/W #16(?) bonding strap.
_____________________________
i knew that much, but because he asked about color coding, i assumed he must be talking about B W Gr because i wouldn't see the point of the question if not.
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winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
For the most common type of MC used, the metallic sheath alone is _not_ recognized as an EGC. For this type of cable, you _must_ use the sheath in combination with the green EGC.
With the newer MC-AP, again, the sheath alone is _not_ recognized as an EGC, but the sheath in combination with the aluminium grounding conductor is an EGC. Additionally the connection to the EGC is made by the cable connectors, not by splicing to the EGC wire.
Apparently with some types of MC that have a _continous_ (rather than a spiral wrap) sheath, the sheath alone is listed and accepted as the EGC.
If the cable does have a redundant EGC, meaning that the sheath alone is listed as an EGC, and the cable also has an insulated green conductor, I don't believe that there is any explicit prohibition against using that _green_ insulated conductor as an _ungrounded_ circuit conductor. But this would strike me as a downright _evil_ installation.
-Jon
With the newer MC-AP, again, the sheath alone is _not_ recognized as an EGC, but the sheath in combination with the aluminium grounding conductor is an EGC. Additionally the connection to the EGC is made by the cable connectors, not by splicing to the EGC wire.
Apparently with some types of MC that have a _continous_ (rather than a spiral wrap) sheath, the sheath alone is listed and accepted as the EGC.
If the cable does have a redundant EGC, meaning that the sheath alone is listed as an EGC, and the cable also has an insulated green conductor, I don't believe that there is any explicit prohibition against using that _green_ insulated conductor as an _ungrounded_ circuit conductor. But this would strike me as a downright _evil_ installation.
-Jon
brantmacga
Señor Member
- Location
- Georgia
- Occupation
- Former Child
i agree --------------
stickboy1375
Senior Member
- Location
- Litchfield, CT
chevyx92 said:
Pretty effective since I don't make a habit of running #10 or #12 for three-ways and/or switch legs...
Don't knock it till you've tried it!
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- Location
- Illinois
- Occupation
- retired electrician
Jon,
I think that there is.
Don
- Location
- New Jersey
- Occupation
- Journeyman Electrician
brantmacga said:
Pigtails aren't required on switches used with metal boxes. And don't you guys use self-grounding receptacles?
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
don_resqcapt19 said:
Why can't all of the color coding requirements be tabulated in _one_ location.
Although to be fair, the 250.119 requirement that Don quoted is _not_ in the 2002 code.
-Jon
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
First of all, as far as I know, only flexible cord considers the EGC when counting conductors, so the 3-conductor cable in the OP should be black/white/red/green. Normally, I use the white as a feed and black as return.
When both 3-conductor cables run to the outlet, the white in at least one cable must be used as a traveler, and using the white in the other cable results in a color change in the travelers, but I also dislike that method.
Therefore, in my opinion, the ideal method here would be to re-color the white to blue in both 3-ways' cables, and use the red and blue as travelers, leaving one black as the supply and the other black as the switch leg.
When both 3-conductor cables run to the outlet, the white in at least one cable must be used as a traveler, and using the white in the other cable results in a color change in the travelers, but I also dislike that method.
Therefore, in my opinion, the ideal method here would be to re-color the white to blue in both 3-ways' cables, and use the red and blue as travelers, leaving one black as the supply and the other black as the switch leg.
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