California 3-way...

[xformer]

Is the "California 3-way" switch wiring permissible according to the NEC?

Let me define a "California 3-way" for the sake of this post. I am defining the California 3-way as : a wiring of 3-way switches where the common terminals and one hot terminal of the switches are used as the travelers for the circuit. The other hot terminal of each switch is connected to the same phase wire that provides voltage to the circuit. The load for the circuit makes connection the traveler that connects the hot terminals together.

With that definition, is a California 3-way permissible according to the NEC?

 

[Dennis Alwon]

Is this what you have? If so it may be complaint with nm cable but not with metal raceways.

Depending on where the neutrals are wired you may have parallel neutrals.

 

[xformer]

I believe a california 3 way is not compliant.

Since all the switching is done in the ungrounded conductor, what code would cause this to be non compliant?

 

[xformer]

Is this what you have? If so it may be complaint with nm cable but not with metal raceways

no, that is not what I am describing. What I am describing is the use of two 3-way switches in a circuit used to control a light while the rest of the circuit continues downstream to feed an additional load.

 

[Dennis Alwon]

Is this it. I would call this a travelling bus 3 way.\

 

[480sparky]

How about this?

 

[Dennis Alwon]

Since all the switching is done in the ungrounded conductor, what code would cause this to be non compliant?

If the neutral were fed thru and tied together on both ends from different place then you would have a parallel path.. 310.4

 

[xformer]

Is this it. I would call this a travelling bus 3 way.\

this is what I am describing Denis.

 

[realolman]

Is this what you have? If so it may be complaint with nm cable but not with metal raceways.

Depending on where the neutrals are wired you may have parallel neutrals.

I must be missing something ... this looks pretty normal to me.... Man, I hope to never come across that other stuff

 

[xformer]

I must be missing something ... this looks pretty normal to me.... Man, I hope to never come across that other stuff

I thought this was normal also.

 

[al hildenbrand]

this is what I am describing Denis.

If you turn off the left hand switch in the post-it sketch, the hot is running on both a traveller and the common to common conductor, which is the parallel condition. 310.4 prohibits conductors smaller than 1/0 from being in parallel.

It was a neat little switching setup in its day.

 

[Dennis Alwon]

I must be missing something ... this looks pretty normal to me.... Man, I hope to never come across that other stuff

Oops I copied the wrong image- oh well.:grin:

 

[Dennis Alwon]

If you turn off the left hand switch in the post-it sketch, the hot is running on both a traveller and the common to common conductor, which is the parallel condition. 310.4 prohibits conductors smaller than 1/0 from being in parallel.

It was a neat little switching setup in its day.

I agree with AL. This is definitely parallel neutrals

 

[hurk27]

Here's what I was always told was a travling buss three way/ tunnel switch?
Flip the first switch and first light comes on, flip the second switch and first light goes out and second light comes on and so on, flip the last switch and last light goes out.

 

[al hildenbrand]

Here's what I was always told was a traveling buss three way/ tunnel switch?

Wayne, it makes sense that the tunnel switching setup would have the moniker "traveling bus", as both the hot and neutral are on the travelers.

I had never heard the term "traveling bus" until an old Forum member, Benny, used the term for this sketch of mine:

This shows an expanded "California Threeway" between two buildings, incorporating 4way and 3way switches, the ability to control lighting in common at both buildings, and to supply receptacle outlets at the far building.

However, the "bus" is a hot on one traveler running between the pair of 4ways, only.

Wayne, I think your application more accurately deserves the title "traveling bus".

 

[xformer]

Thanks Al, and Dennis for the explanation.

 

[jap]

If you turn off the left hand switch in the post-it sketch, the hot is running on both a traveller and the common to common conductor, which is the parallel condition. 310.4 prohibits conductors smaller than 1/0 from being in parallel.

It was a neat little switching setup in its day.

I agree that this creates a parallel condition in "that particular part of the circuit", but, what harm does that cause? It's not like where you use 2 smaller parallel conductors from the beginning,to add up to the amperage of a larger conductor. To me, "Both Ends" would mean starting at the breaker with parallel conductors to the first termination point,like you would if you were parralleling (2) smaller conductors to take the place of a larger conductor on a large feeder.On this circuit it starts out as a single conductor then gets paralelled in the middle.

 

[George Stolz]

To me, "Both Ends" would mean starting at the breaker with parallel conductors to the first termination point,like you would if you were parralleling (2) smaller conductors to take the place of a larger conductor on a large feeder.On this circuit it starts out as a single conductor then gets paralelled in the middle.

Submit a proposal to change the wording of 310.4 to allow conductors to be installed in parallel if each conductor is rated according to the OCPD. Until the code definition is changed, then it is as Al and Dennis say: an extremely small misinstalled parallel conductor.

Bear in mind, 300.3(B) already puts some constraints on this principle.

 

[480sparky]

Submit a proposal to change the wording of 310.4 to allow conductors to be installed in parallel if each conductor is rated according to the OCPD. Until the code definition is changed, then it is as Al and Dennis say: an extremely small misinstalled parallel conductor............

The language already exists. It just doesn't allow it for supplying receptacles and luminaires.

 

[Dennis Alwon]

I agree that this creates a parallel condition in "that particular part of the circuit", but, what harm does that cause?

Well it probably does cause harm directly but it will create unnecessary electro magnetic fields. I for one would prefer not to have them in my house however the NEC is silent on that issue.