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Wiring help: (2)3 way/(1)4 way switches for 3 dual fluorescent 4'40 watt on 20@br

Wiring help: (2)3 way/(1)4 way switches for 3 dual fluorescent 4'40 watt on 20@br


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Old 05-16-03, 08:32 PM
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Wiring help: (2)3 way/(1)4 way switches for 3 dual fluorescent 4'40 watt on 20@br

1.) Wiring of (2) 3-way switches & (1) 4-way switch with 3 each, 4 foot dual fluorescent fixtures. Is the following correct? Breaker box (Power) to first 3-way switch thru 1/2" EMT into top steel switch box, using one NM-B 12-2 w/ground to switch. (White) Neutral wired all the way thru (bypassing switches) for all switches. Out feed (Black, Red & Ground) to 4-way switch from first 3-way switch, thru side of 3-way switch box with 90 degree EMT fitting, using seperate 1/2" EMT, using NM-B 12-3 w/ground. Connect to 4-way switch in thru top of 4-way switch box w/1/2" EMT, outfeed from opposite side of 4-way, thru side of 4-way switch box with 90 degree EMT fitting, also with seperate 1/2" EMT, also using NM-B 12-3. Here is the unusual part. Since the final 3-way switch is over 40 feet away, to save on EMT, the NM-B 12-3 from the 4-way switch was run thru the lights (all of which were connected with EMT), WITHOUT connecting 12-3 feed run to ballasts. Wire was run as unstripped NM-B, to the third 3-way switch.
Now, IF I cut the 12-3 at each light, wire nutted the red to red at each cut, and black to black at each cut, for a pass thru (without connecting them to the lights ballast at this point); but connecting the white and ground at each light, as I go, and terminate the white (neutral) the last ballast. The ground would also pass on thru to the final 3 way switch, from the last light ground connection. At that point, the 12-3 NM-B would be proceeding thru the final 8 feet of EMT to the final 3-way light switch, with the red, black and ground going as previously described, as a pass thru to the incoming feed side of the switch. The CUT white going thru the final 8 feet of EMT to the final 3-way switch would NOT have been connected to the termainated White at the last ballast, it would be an empty wire. That particular white wire would be taped with purple and black tape at each end (for identification as a return hot), and used as the return feed "black" for the light ballast, to complete the circuit. From each light ballast, a SINGLE black wire would be wire nut connected to the "white converted to black" and run to connect each light's ballast with an individual black wire back thru the EMT, and terminate on the final ballast going the other way. With this scenario, could I get by with running a single black wire thru the lights connecting EMT tubing, eliminating the over crowding of the EMT at the final 8 foot run of the tubing. Would this seem acceptable???
 
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Old 05-16-03, 08:55 PM
J
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Is conduit required in your city? What city is that?

Just for the moment, ignore conduit fill rules.

Code does not allow a white wire, even a reidentified one, to feed power back from the far 3-way switch. In that final segment between the last light and the far 3-way, you'll need to use the white as one of the travelers and return the power on the black or red. You still must reidentify the white wire as you indicated.

Since you are using conduit, I'm not sure why you're using 12/3 and 12/2 at all. Sure you can run that individual black wire, but why didn't you just run all individual wires and skip the NM-B?

Okay, now let's quit ignoring conduit fill rules. Even without the extra black wire, 1/2" EMT is too small for 12/2 or 12/3. You have a conduit fill violation. So you now have two options: (1) increase the conduit size to 1" (3/4" is big enough for those segments without the extra black wire), or (2) get rid of the NM-B and run individual strands of THHN.

I think option (2) is going to win hands down. And that will eliminate the need to reidentify any wires, since there will be no need to use any white wires to the far switch.
 
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Old 05-17-03, 08:01 AM
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