Electrical question - adding a neutral

[gfretwell]

John you can also wire a 3/4 way switch loop with the hot going down and the travelers coming back. (or the other way, travelers going down, switched leg coming back)

[John Grabowski]

*Yes, but based on the wiring diagram the OP presented, I'm not sure what he already has in place. He is only showing a two wire in and a two wire out at the 4-way. Maybe that is why a neutral at the load side was borrowed from another circuit.

[Nate Nagel]

I'm thinking that this is actually a hybrid of that and the standard configuration, since the OP said that there were neutrals in two of the boxes but not another - panel box -> switch 1 -> switch 2 -> light fixture -> switch 3

so if that is the case he will have to repull the cable between the light fixture and switch 3 but that is just supposition at this point

nate

[RBM]

Yeah, that was my first favorite thing. The hammer drill and 3/16" carbide bit. Throw that star drill away!!

[Gordon Shumway]

I am definitely NOT sure it's not a switch leg. I am positive both diagrams are correct. The sensors work as they should when I temporarily borrowed an existing neutral at the two locations that didn't have it for that circuit.

We bought the house when it was new forty years ago. Did the NEC require a neutral at the family room location then?

[Nate Nagel]

There are situations where a neutral may not be required to be present, but if your diagram is accurate then it is. The requirement (prior to the current NEC) is not that the neutral to be present, but that all the conductors in a cable sum to zero (to minimize potential inductive heating.) So the neutral needs to be present in the cable running from the "hallway" switch to the "family room" switch and likewise from the "family room" to the "foyer." Otherwise let's just say for the sake of argument that it's a 120W light bulb to make round numbers, you'd have

1A flowing through the "hot" traveler in each cable and no current in the disconnected traveler - that doesn't sum to zero. Likewise you have a neutral with a -1A current somewhere else. (I know it's AC, I'm just using the convention of "hot" = positive and "neutral" = negative for purposes of simplicity, since the currents will in actual fact oppose each other at all times) That's not legal...

However, disassemble the family room switch box again. If your diagram is truly correct, the neutral should be there, and spliced through (likely with a wire nut, if the house is only 40 years old) hidden in the back of the box.

nate

[gfretwell]

I looked at your picture. Is the neutral in that diagram running along with the travelers in the same cable? If not, that is a violation.

300.3(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord,...

[trader4]

Just out of curiousity, how does the above play with DerbyDads recent question about adding a seperate ground wire to add a ground to a run of romex that currently does not have a ground?

And even if you could add a seperate ground wire, doesn't that wire have to be protected, ie either already in a romex or else run in a conduit, etc?

[Nate Nagel]

Ground is different as it is not normally a current-carrying conductor and therefore is considered to have zero current. Now I don't remember the details but I believe that for new construction you are still supposed to pull the ground in parallel with the other conductors but for retrofitting a ground you are allowed to get it from wherever you can

nate

[gfretwell]

Correct, there is an exception for adding a ground to an ungrounded system

250.130(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions. The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following: (1) Any accessible point on the grounding electrode system as described in 250.50 (2) Any accessible point on the grounding electrode conductor (3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates (4) For grounded systems, the grounded service conductor within the service equipment enclosure (5) For ungrounded systems, the grounding terminal bar within the service equipment enclosure.

[bud--]

It was added in 2011 (or maybe 2008).

A possibility that would make sense of how the wiring is shown is if all

4 wires of the 4-way run go to a light fixture (or other common-point box) that both 3-ways connect to. The 4 wires could also go to one of the 3-ways (but this would likely be seen in Gordon's diagram). The current sum of the 4 wires from the common box to the family room would be zero. If wired this way the 4 wires could be reconfigured to work with the sensors.

If wired that way, the 4 wires could be run under the current NEC with 2

2-wire Romexes (with conditions) under 300.3-B-3.

Otherwise I agree with everyone that the wiring violates the NEC.

What is the wiring method (Romex, EMT, ...)?

Are there other wires at the locations?

========================== I would not use the neutral of another circuit and would not recommend anyone else do it. But the minor load from the sensor would not overload either circuit or cause inductive heating. It might trip a GFCI (5mA trip). It would likely not trip an AFCI. (An AFCI also has a ground fault trip included - usually at 30mA.) It might cause a shock hazard when working on the wiring.

[Gordon Shumway]

I have done some more investigation and have discovered I could be wrong. I can't believe I said that. Thank you Nate, for encouraging me to look deeper.

My original conclusion was the wires going to the load originated at the box in the foyer I believe is wrong. The wires going to the load originate in the hallway.

I have uploaded a revised image to:

What is the red wire going to all of the boxes and presumably the load?

[RBM]

That diagram has the correct wires, except for the three wires going to the load. There should only be two unless they're carrying a feed to go somewhere else. The red wire, the way you drew the diagram, would be the common, and would just be spliced through at the 4 way.

[John Grabowski]

*Much better. The red wire appears to be the load as it is spliced through to the last 3-way and should be attached to the darker screw on the 3-way switch. As RBM pointed out, the three wire going to the lights has a line, load, and neutral wire. It is also possible that the hot and neutral comes from the light to feed the switches and the red is the load returning to the light.

Based on the diagram that you provided from Pass and Seymour, you may be able to install the 3-way motion sensors after changing the splices so that you have a hot (Black), neutral (White), and traveler (Red connected to yellow) at each box. The load (Red connected to red) gets spliced at the one box. This appears to be a digital control and not entirely mechanical which would require a fourth load wire at each location.

[trader4]

And if that one won't work under those conditions, Lutron Maestro series has a multi location dimmer that include a motion sensor, will work CFL, etc, requires only hot, neutral and one wire between switches and you can hook together up to 10 of them that way. That series of dimmers is really nice.

[Nate Nagel]

Looking at that now, if the white is one of the travelers in all boxes, it would appear that the whole thing is a long 3-way switch leg with no neutral. I think at this point the next step is to drop the light fixture and see what's in there. The only thing that doesn't add up now is the red in the cable going to the load, that only needs to be a

2-wire cable (by the old code.)

What I suspect that you'll find is the line coming into the ceiling box, a 2-wire cable going to the first switch location, then a 3-wire cable (I'm not counting grounds in any of this) going to the other two switch locations.

The red wire in the 3-wire cable, and then one of the wires in the

2-wire cable (I've seen it done both ways) will be the switched hot returning from the last 3-way to the load in the ceiling box. the other wire in the 2-wire cable is unswitched hot.

nate

[Nate Nagel]

This might make what I was suggesting more clear.

Unfortunately, if I'm right, you've got three runs of cable to repull.

(my apologies for quick and dirty sketch, but for things like this I'm far more comfortable with a drafting pencil and cocktail napkin than a computer program...)

nate

[John Grabowski]

*I see no reason to pull any new wires. Based on the information that Gordon has provided, he has the necessary conductors. He just needs to change a few splices. He needs to connect all of the whites together in the box with the line and load which will give him a neutral at each location. The blacks get connected together to provide a hot at each location. The existing red wire that goes from switch to switch gets connected to the yellow on the motion sensor. The red on the motion sensor in the box with the line and load gets connected to the red going to the lights.

[bud--]

I don't think the details, including switch connections are shown correctly at the right end box. Is there only one (3-wire) run? The wires (but not connection) make sense if there is another 2-wire connection and power feeds through the box. Otherwise, as Nate says, there only need to be 2 wires to the light.

*IF* the number of wires shown is correct the P&S devices can be used. As John notes, these are not normal 3-way switches. Contrary to the labeling on the P&S diagram, The sensors interconnect with a hot, neutral and control wire. The singe control wire switches the devices between on and off. There need to be 3 wires between devices (which there are). At the right end feed point there need to be 3 wires (hot, neutral and switch leg) to the light, which is what the diagram shows.

[RBM]

If he definitely has three wires going from the end switch to the lights, it's either got to be bringing a feed and switch leg up from the switch or down from the lights, either way the devices will work as John describes