Gretings
I am sure we have discussed this before...
I am of the opinion that 2 wire NM travelers for 3way & 4 way switching are not allowed by the NEC. I am hanging my hat on 300.3B. However, could 300.3B3 allow the use of 2 wire NM cable for 3 way systems? If so, was this a change from previous codes?
I have a contractor that did all 3 & 4 ways with 14-2 NM travelers. I red tagged citing 300.3B. I expect him to contest this, and he probably will argue that 300.3B3 allows this method. I do not believe that it does allow this, just looking for opinions/ reinforcement. I do not want to have him change this if somehow it meets minimum code.
Thanks
Rick

I see that 300.3(B)(3) refers to 300.20(B). Is the contractor going to claim that the latter rule allows this, so long as he has taken the necessary steps to reduce eddy currents?

Is it even practical to cut slots or otherwise modify a box where NM cable clamps are used?

Pauluk
Contractor is using plastic boxes.
Waddya think?
Rick

I would not do this but I do believe it is allowed.

I think you will have to live with it.

300.3B states all conductors to be in the same cable, unless otherwise permitted by 300.3B 1-4. 90.5B (permissive rules) need the use of the twerms "shall be permitted", & "shall nmot be required". I do not see where this is specifically permitted.
Rick

Rick,
300.3(B)(3) is the specific permission. With nonmetallic raceways or cables all of the circuit conductors are not required to be in the same raceway or cable as long as 300.20 is complied with for metallic boxes. There are no metallic boxes in this installation so there is no violation.
Don

Rick, even though this is code compliant, you should mention to the electrician the "net current" and EMF issues that would be associated with this wiring method.

Tell him that even though the research is not conclusive at this time, EMF is suspect by some to be a contributor in leukemia in children and let his conscience tell him what to do.

Roger

Assuming all cables for the run are in very close proximity to one another between plastic boxes, IMO there are no concerns about eddy currents or EMF. The intent of requiring all conductors to be together is to eliminate the EMF, this is met by running both cables side-by-side between boxes. What difference is there in this from running four conductors and a ground in PVC?

Earl

Earl, for two wire travelers it is not possible to do what you suggest.

The neutral must have stayed at the fixture, feed the three ways at one end and from the other end back to the fixture.

Earl, as as Bob said, it would be unlikely that one set of two wire travelers would be running along side of current canceling conductors of which would pass by the end three way box.

If this was the case I agree that there would be no issue, but I just don't see where it would exist.

Roger

Does anyone see any issues with using 2 lengths of 2-conductor NM cable to a 4-way switch?
No neutral being carried to the 4-way switch. Just 2 sets of travelers.

BTW,
Would the new 4-conductor NM Cable make this more acceptable?

[This message has been edited by Redsy (edited 02-08-2004).]

It is a lot like knob & tube wiring method I guess, only with nonmetalic boxes.
The method this contractor uses is to feed a 3 way from the nearest circuit, & grab a neutral (not necessarily from the same circuit), from another convenient nearby box.
Regarding my 1st post... he has changed to all 3wire travelers.
Rick

Oh, I see now. That is just lazy wiring. Grab a neutral from any convenient box? No way.

Earl

Hi Rick,
A two wire traveler, according to 404.2(a) exception is not required to have a grounded conductor ran in the same cable. I would reject the installation for grabbing another neutral from a different cicuit or require a double trip device to kill the power from the other circuit as required under 210.4(c) exception #2

From what our NEC experts have said, it sounds as though it would be code-compliant, but I would not run travelers like this unless the wiring could be so physically arranged as to have the return conductors running adjacent throughout.

It used to be pretty common in the U.K. for lighting circuits to be wired with travelers like this or with single conductors from 3-way switch to lamp and so forth (particularly in the days before grounds were required to be run on lighting circuits).


If the two runs are bundled together throughout and run from the 4-way back to the same box for splicing into an existing 3-way circuit, then the fields should cancel out just fine.

pauluk,

What you describe is just what I meant.
The current carrying conductors would be in different cables, but stacked together, and therefore in close proximity.
There is a 4-wire NM cable on the market over here now. If there are any concerns about the separate cables, this would seem to be the solution.

I think Redsy is talking about a 14-2 set of travelers going to a 4 way from 3 way #1, & a 14-2 set of travelers leaving the 4 way going to 3 way #2. This is no different than the 2 wire travelers between the 3 way switches.
Mountainman, 404.2 referrs to switch loops only... not travelers. Respectfully,
Rick

Looks like your posts crossed within a few seconds of each other.

Agreed. If the two cables leave the 4-way in different directions, then there will be a resultant field from the single conductor on each cable which is carrying current at any instant.

That new 4-conductor Romex sounds quite handy.

"Mountainman, 404.2 referrs to switch loops only... not travelers. Respectfully,
Rick"

If travelers are not part of the switch loop, then what are they?

Rick, a switch loop would have current flowing in oposite directions at the same time in two conductors, thus canceling each other.

In a set of travelers, current only flows in one conductor at a time.

Roger

maybe you could use a coast 3-way system. This systems has no "travelers" only a hot, switch leg, and a common. ( Note the common is not a neutral This is a code legal 3 way system )

dfe,

What is a "coast" system, and how does it work?????



Peter

Hi Peter

A coast 3 way is just one of 3 ways to hook up a 3 way ( someone once told me that why it called a 3 way " you can hook it up 3 different ways...I don't know if this is true ). Only two of the 3 are nec approve.

the coast 3 way uses the same type of swith- spdt its just wired different

Standard system
switch "a" hot to common, travelers to t1 and t2 switch "b" switch leg to common travelers to t1 and t2
coast system
Switch "A" hot to t1 switch leg to t2, common join to common of switch "B" hot from switch "a" join to switch "b" t1 much like a traveler would, the switch leg from switch "a" follow in the same manner to switch "b" t2.

maybe it may be better to say
Join common to common
Run your hot and switch leg the way you would you travelers.
what is neat about this system is you have you hot a switch leg on both ends, and in the middle as well. lets say you have a light above each 3 way and a 50' long hallway with a few lights alone the way. with only 4 wires running from box to box you have all you need.The neutral stays white, you make the black the hot red is the switch leg blue as the common. Using the coast as you can see save the "I start my 3way here with the hot and end it there with the switch leg and pull the switch back to the other light back at the start. then I'll run the hot over to the other end for my other light switches". With the coast system you have what you need at both ends.

hope that this will help its hard to explain this with text, If you and I was at a job site this would be a simple drawing on the wall.

Found this link through the current 3-way thread.

Never though of the coast system of 3-way wiring, nice tool to have in my arsonal now

The only problem is that in the 2nd configuration the run could be 150% longer than the traditional method. Would be a bit confusing to the trouble shooter why in one position the lamp is dimmer than in the other position

Let me know if I got my diagrams wrong from your descriptions dfe, but they appear to be correct.






[This message has been edited by dmattox (edited 07-09-2005).]

Bah, UBB > me tonight

Ignore this post!

[This message has been edited by dmattox (edited 07-09-2005).]

Some of my worst nightmares have been troubleshooting weird switching circuits. Sometimes the conclusion was that the wiring was never right to begin with...there were not enough wires to do what had to be done, but no one ever really noticed until now that "With this switch down you can't make the other 2 switches that go to the hall lights work."

I appreciate knowing all these ways of doing it, but still maintain that wiring 3 and 4 way switches is not the time to show how creative you are.

So true poorboy, with how much my guys miswire normal 3-way switches, I don't think I would ever do a coast system. But, its good to know how someone might do it.

Another problem with the coast system is that you can't add a 4-way switch without redoing the whole thing. Or at least I can't figure out a way to do it.

As an EC, it's very refreshing to go on a service call where a homeowner has tried to replace a three-way or four-way switch and find the original EC used standard methods and simple color coding (travellers with matching color---a different color than the power). I can install the switch correctly without tracing the wiring.

Dave

I've had to rewire 3-ways where we used color coded travelers and some of my guys still screw it up

I found a "coast" a few years ago in Cape Coral while sorting out a 3 way replacement gone bad for a friend. I really didn't know what happened or how it ever worked until I saw this picture. I just pulled out both switches and started over with the "normal" method.

So has anyone else figured out a method for more than two locations, or a four-way? I am a little hung-over from a wedding last night, and just can not grasp the concept.

That, and how would any other than Maestro dimmers work on this?

And does this bear any relationship to the "Hollywood" 3-way?

Whenever I wire for a 3-way, or 4-way lighting set-up, I always bring the feed and switch leg to the same box so at the end of switching it'll be a dead end. Doing it this will simplify any troubleshooting that needs to be done later.

Of course, sometimes because of box fill it can't always be done this way. If that's the case, I feed at the light box and bring down (2) 3-wire dead ends to each switch location.

As far as I know there are (4) ways to wire a 3-way switch design.

I have. You can insert one in the travelers in the usual way, as long as it's done at either end, i.e., between the lamps and either (or both) of the 3-ways.

If you place a 4-way between the lamps, then one will stay on all the time with the 4-way in one position.

Ah, you're a wise man Larry, I spent way too much time trying to figure out a way to do it