Is a "dead-end" three-way switch legal?

[JoeNorm]

A very experienced electrician taught me "dead end" three way switch wiring. It seemed like a really useful way to do it. Then I leaned that we're supposed to have a neutral at each box. Since the white wire gets re-identified as black in this method that means there is no neutral in one of the boxes.

He is a very "by the book" electrician so I was surprised he would do something not to code.

Thoughts?

 

[ptonsparky]

Neutrals were not always required at switch boxes. I have never heard the ‘dead end’ term before but I suspect most were that way.

 

[480sparky]

A 'dead-end' 3-way is one which only has one cable in the box.... the xx/3 from the other switch. The feed and switched circuit are both in the other box. Dead-ends are perfectly legal. But to compy with Code now, you need to consider having the circuit neutral in the box as well.

If the dead-end 3-way is fed using NM cable and is in a finished portion of the structure, then you'll just need to use 4-conductor cable (Bk/W/R/Bl). If it's in a raceway, you probably won't need to supply the neutral at the switch.

 

[curt swartz]

404.2(C)
(C) Switches Controlling Lighting Loads.
The grounded circuit conductor for the controlled lighting circuit shall be
installed at the location where switches control lighting loads
that are supplied by a grounded general-purpose branch circuit
serving bathrooms, hallways, stairways, or rooms suitable for
human habitation or occupancy as defined in the applicable
building code. Where multiple switch locations control the
same lighting load such that the entire floor area of the room
or space is visible from the single or combined switch locations,
the grounded circuit conductor shall only be required at one
location. A grounded conductor shall not be required to be
installed at lighting switch locations under any of the following
conditions:

(1) Where conductors enter the box enclosing the switch
through a raceway, provided that the raceway is large
enough for all contained conductors, including a grounded
conductor

(2) Where the box enclosing the switch is accessible for the
installation of an additional or replacement cable without
removing finish materials
(3) Where snap switches with integral enclosures comply with
300.15(E)

(4) Where lighting in the area is controlled by automatic
means

(5) Where a switch controls a receptacle load

 

[kwired]

404.2(C)
(C) Switches Controlling Lighting Loads.
The grounded circuit conductor for the controlled lighting circuit shall be
installed at the location where switches control lighting loads
that are supplied by a grounded general-purpose branch circuit
serving bathrooms, hallways, stairways, or rooms suitable for
human habitation or occupancy as defined in the applicable
building code. Where multiple switch locations control the
same lighting load such that the entire floor area of the room
or space is visible from the single or combined switch locations,
the grounded circuit conductor shall only be required at one
location. A grounded conductor shall not be required to be
installed at lighting switch locations under any of the following
conditions:

(1) Where conductors enter the box enclosing the switch
through a raceway, provided that the raceway is large
enough for all contained conductors, including a grounded
conductor

(2) Where the box enclosing the switch is accessible for the
installation of an additional or replacement cable without
removing finish materials
(3) Where snap switches with integral enclosures comply with
300.15(E)

(4) Where lighting in the area is controlled by automatic
means

(5) Where a switch controls a receptacle load

:thumbsup::thumbsup: Also note the portion I bold faced.

 

[winnie]

The justification for the 'have a neutral' requirement is new lighting controls which themselves require power.

A mechanical '3 way switch' does not require power and does not require a neutral. But things such as 3 way dimmers _do_ require power to operate. The power needed is so low that 'leakage' to _ground_ was often used as the source, and this was seen as a problem. Thus the requirement to have a neutral _available_.

It looks like the code as written is trying to be reasonable about the 'availability' of this likely unused neutral. You only need it at one switch location if there are multiple. You don't need it if you use raceway where one can be pulled in later.

-Jon

 

[Dennis Alwon]

1

 

[480sparky]

.........

Here is the typical install

A big advantage to this type of install is both locations wire up identically. So you can teach the new guys how to make it up and trim it, it doesn't make a difference which switch they're working on.

 

[kwired]

A big advantage to this type of install is both locations wire up identically. So you can teach the new guys how to make it up and trim it, it doesn't make a difference which switch they're working on.

I think they still need to learn those other methods even though they are no longer going to be compliant most of the time, it will help troubleshoot existing installs, otherwise they will think it was never installed right and never worked in the first place.


Add: I think it is more important to have the logic soak in regardless of wire/cable paths, it makes it simpler IMO. Once you get that logic in your mind then you can throw in different scenarios that take into consideration that you need a return path in same raceway/cable to minimize EMF effects, how to route things when the load is closer to the source than the switch(es), etc.

 

[480sparky]

I think they still need to learn those other methods even though they are no longer going to be compliant most of the time, it will help troubleshoot existing installs, otherwise they will think it was never installed right and never worked in the first place.


Add: I think it is more important to have the logic soak in regardless of wire/cable paths, it makes it simpler IMO. Once you get that logic in your mind then you can throw in different scenarios that take into consideration that you need a return path in same raceway/cable to minimize EMF effects, how to route things when the load is closer to the source than the switch(es), etc.

True, but teaching them the quick n easy way first gets them to be productive right out of the chute.

 

[ptonsparky]

True, but teaching them the quick n easy way first gets them to be productive right out of the chute.

Agreed, Q&P, but we had ropers that had no idea what or how to proceed should they encounter something different. Not complaining, it kept me employed.

 

[kwired]

True, but teaching them the quick n easy way first gets them to be productive right out of the chute.

If on the job training then yes.

If in a school you usually teach basic concepts then go to the lab to apply them to real life situations or at least some sort of mock up.