ECN Forum Forums Technical Discussion Electrical Theory and Applications wiring a three way switch

Yes -- Either tape or a short length of red sleeving.

Sparky66,

I've used the old standard black Sanford markers for years (way before it was an NEC requirement), and have never noticed any degradation of the insulation. I have however noticed on several occasions plastic electrician's tape where the adheasive has become gummy and the tape itself has become brittle and unraveled in just a few short years. I would think that the solvents that are used in some paints would be just as harsh as the inks used in marker pens, and the NEC specifically mentions painting as one of the effective means to permanently reidentify the conductor. I contend that when code making panel No. 5 decided to use the wording "permanent means", they meant permanent.

Sparky,

The requirement for the white conductor to only be used as a supply to the switch and not the return to the outlet was not new in "02". The oldest code book that I own is a 1975 edition, and its there in 200-7, exception #2 with no change bar in the margin along side, so it had to be a requirement even in the 1972 edition. In those days however, the NEC specifically added that reidentification for use in a 3 or 4-way circuit was not neccesary.

Granted, these are minor violations, but nonetheless they are violations.

Matt

Boy, I still don't get it.

Here. . .string together the emphasized words of (C) with the emphasized words of (1), and second, string the emphasized words of (C) with the emphasized words of (2).


The supply to a switch, switch leg and travellers are all ungrounded conductors (except for some arcane K&T situations). Re-identify the white used in any of these and (C)(1) is satisfied.

(C)(2) is a special subset of (C)(1). The switch supply wire is ungrounded. (C)(1) has already told us to re-identify it if it is from a cable and it is white. But, just to make it crystal clear, (C)(2) describes the 1996 200-7 Ex. 2 and earlier practice where the "white" had to be the supply by the 1996 and older language.

By way of further, redundant, crystal clarity, the 2002 NEC Handbook says after 200.7(C)(2):


This would allow the last threeway circuit diagram the Matt first talks about at the top of this thread to be correct as shown.

Al

Al,
I don't see (C)(2) as a special subset of (C)(1). In my opinion the intent of the code is that the white only be used as the supply to the switch, when part of a cable used for switch loops. The only change that was made in the '99 code was to require that the white when used to supply the switch be reidentified as a hot. In the earlier codes the reidentification was not required.
You use (C)(1) for cables that are mot part of switch loops where the white is not used as a grounded conductor. You use (C)(2) with cables used for switch loops and the white is used as the supply to the switch.
Don

What Don said! LOL

(C)(2) is not a subset of (C)(1).

(1) and (2) are both subsets of (C), which is a subset of 200.7.

A good example of an application using (C)(1) is where a 2 conductor romex is used on a 240 volt branch circuit.



[This message has been edited by Matt M (edited 08-01-2002).]

I must be really thick headed. Please bear with me. . .

Set one = All white wires in cable assemblies

Set two = cable assembly white wires used as ungrounded conductors

Set three = cable assembly white wires that are ungrounded that are used in switch loops

Set four = cable assembly white wires that are ungrounded that are used in switch loops only to supply the switch but not as a return from the switch to the outlet.

Set five = cable assembly white wires that are ungrounded that are used in switch loops as a traveller between 3ways and 4ways.

Set 1 contains all of 2, 3, 4 & 5
The part of Set 1 that is NOT 2, 3, 4 & 5 = plain old grounded conductors

Set 2 contains all of 3, 4 & 5

Set 3 contains all of 4 & 5

Set 4 & 5 do not intersect (can't use a supply as a traveller - except maybe in a california 3way).

Here's my point, cable assembly white wires that are ungrounded that are used in switch loops only to supply the switch but not as a return from the switch to the outlet (Set four) is completely contained inside the set of all cable assembly white wires used as ungrounded conductors (Set two).

Seems to me that (C)(2) is a subset of (C)(1), and both (C)(2 & 1) are subsets of (C), which is all white wires.

Switch legs are ungrounded conductors.

Or to say it another way, if I don't set up my cables and their conductors in a switch loop with 3ways and 4ways so that the former white conductor is used only for the switch supply or the traveller, because I have re-identified the white conductors I can use them as ungrounded conductors to the end that I need, i.e., getting the light to work when I flip the switch.

Electrical,

I guess I don't see what you're missing.

200.7(A) explains that the conductors as outlined in (1), (2), and (3) shall only be used as the grounded circuit conductor, UNLESS otherwise permitted in 200.7(B) & (C).

200.7(B) deals with circuits of less than 50 volts, and does not apply here.

200.7(C)(1) is just saying that where the conductors that were outlined in 200.7(A)(1), (2), and (3) are part of a cable assembly, and they are used as an ungrounded conductor, they must be permanently reidentified.

200.7(C)(2) is saying that where the conductors that were outlined in 200.7(A) (1), (2), and (3) are part of a cable assembly AND are used for a single pole, 3-way, or 4-way switch loop, that these conductors not only must be reidentified, but they must also only be used as the supply to the switch, and not the return from the switch to the outlet.

200.7(C)(3) deals with flexible cords, and does not apply here.

Another thought on the possible intent that code making panel #5 had when they included the term "permanent means" in the wording of 200.7.

Comparatively, lets examine the wording of 200.6(B), where conductors of sizes larger than #6 are used as a grounded conductor.... sort of the reverse in effect (use of white tape IS and has long been an acceptable means here).

Nowhere in this section does it use the term "permanent means". It only requires that at the time of installation, the conductor be identified by a "distinctive white marking" at its terminations. Matt

Thanks Matt,

How's the weather by the Lake? It's drying out nicely down here.

I don't see what I'm missing yet, either.


Ex. 3 & Ex. 4 don't pertain at the moment.

200-7 by itself, not looking at the exceptions, hypothetically, says the white or gray can only be used as a grounded conductor. (That's in raceways, cables, cords, whatever, no limits are posted on the statement.)

Adding Exception 1 modifies the blanket statement of 200-7 by allowing a white or gray to be used as an ungrounded conductor when it is re-identified. Now, if this is where section 200-7 ended, we would've been always re-identifying the white in a cable assembly whether used in a switch loop or not. (Again, this Exception applies in raceways, cables, cords, whatever.)

Adding Exception 2 modifies both 200-7 and 200-7 Ex 1 together by allowing cable containing a white or natural gray conductor not to be re-identified when installed as described. This is the exception for the exception. IMO. As long as I carefully install the white, I don't have to re-identify it. I can re-identify it if I wish to take the time. If I re-identify the white wire, I am complying with exception 1. I "shall be permitted" to not re-identify. Notice that Ex. 2 doesn't say "I shall not re-identify". Re-identification "shall not be required" is totally different than: Re-identification shall not be done."

You know? As I get into this I don't even see where 1996 requires a re-identified white in a cable to only connect as the supply for a switch. The option to not mark the white is given when it comes from a cable and is installed in certain places in the switch loop. That's all.

Fascinating.

Sorry for the length. I got wound up. Mmmm, strong coffee is Good coffee.

Al

OK. I just chased the language back to 1956.

From 1975 through 1996 the language doesn't change except in 1987 where "outlet" in 200-7 Ex 1 is changed into "location".

Other than that one word, 200-7, 200-7 Ex 1 and 200-7 Ex 2 don't change until way back in the 1971 NEC.

And it's an interesting change. Note: "identified" = grounded, and "unidentified" = ungrounded.

In 1971 200-7 Ex 2 has a fine print note. Here's the thing in it's total:

This FPN is the same back in the '56 NEC.

Seems clear to me the CMP's intent was to save sparky a bit of labor when installing switch loops, rather than restrict the use of the re-identified white to supply of switch only.

Al

[This message has been edited by ElectricAL (edited 08-01-2002).]