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-   -   2 lights, 4 3-way switches (http://www.diychatroom.com/f18/2-lights-4-3-way-switches-193370/)

dgfit 01-05-2014 10:08 PM

2 lights, 4 3-way switches
 
Light at top and bottom of stairs.

Two switches at bottom of stairs (one switch for light at bottom of stairs and one for light at top of stairs)

Two switches at top of stairs (one switch for light at bottom of stairs and one for light at top of stairs)

Is it code compliant (2000 cycle) to do the following?

Bring power into box at bottom of stairs with 14/2 to feed both switches and provide a neutral
Run two 14/3 cables from bottom switch box to top switch box used as follows:
Cable 1 carries two travelers for one set of switches and a neutral
Cable 2 carries two travelers for the other set of switches, but repurpose the white wire (marked with black tape) to bring switched power from top switch back to bottom box

Run two 14/2 cables as follows:
Cable 1 from top switch box to top light (neutral and switched power from one top switch)
Cable 2 from bottom switch box to bottom light (neutral and switched power from other top switch via repurposed white wire)

This would give me a neutral in both switch boxes and both lights, and I think is the minimum number of NM cables. Would this create any problems with false AFCI trips?

Are there any better ways to do this?

dgfit 01-05-2014 10:13 PM

Oops - I meant 2011 code cycle

k_buz 01-05-2014 10:28 PM

I can't see anything wrong with it.

Philly Master 01-06-2014 05:40 AM

or 2 ......14/4 wires ... or 14/2/2 which ever is available locally

http://www.homedepot.com/p/Southwire...255/203641719#

dgfit 01-06-2014 08:11 AM

If I were to use 14/4, wouldn't I just use 1 14/4 and a 14/2?

The 14/4 cable would be the 4 travelers (with the white wire repurposed)
The 14/2 cable would be neutral and return switched power

joed 01-06-2014 08:28 AM

You are fine except for one thing. Use the remarked white as a traveller instead of return power.

jbfan 01-06-2014 09:15 AM

Why return power?
Run 14/2 from top switch to each fixture.
This eliminates having to remark or re-purpose any wire.

dgfit 01-06-2014 09:41 AM

Quote:

Originally Posted by jbfan
Why return power? Run 14/2 from top switch to each fixture. This eliminates having to remark or re-purpose any wire.

I could, and may still do that. It just means I would have one of two configurations between switch boxes that would result three cables instead of two, and also either an unused wire or (still) a repurposed wire:

Configuration 1:
14/3 carrying two travelers and a neutral
14/3 carrying two travelers and an unused white wire (or run it as a "parallel neutral")
14/2 from top box past bottom box to bottom light (with neutral and switched power)

Configuration 2:
14/3 carrying two travelers and a neutral
14/2 carrying two travelers (with white wire repurposed)
14/2 from top box past bottom box to bottom light (with neutral and switched power)


The bottom line is 5 conductors are required between switch boxes and there is no such thing as a 14/5 cable. I agree it would be least confusing to others to go with configuration 1 but it just seems wasteful to have an unused wire, or silly to have two wires run between the two boxes and simply connect them together in each box.

dgfit 01-06-2014 09:44 AM

Quote:

Originally Posted by jbfan
Why return power? Run 14/2 from top switch to each fixture. This eliminates having to remark or re-purpose any wire.

The "return power" would be from the top switch and then spliced to the cable from the bottom box to the bottom light.

jeffnc 01-06-2014 10:04 AM

Assuming you are on a 15 amp circuit.

Jim Port 01-06-2014 10:17 AM

The simplest way to provide a neutral at each box is to bring power into SW1 on a xx-2. Then run a xx-3 between SW1 and SW2. From SW2 to fixtures on a xx-2. The white stays as a neutral throughout.

joed 01-06-2014 10:34 AM

Quote:

Originally Posted by dgfit (Post 1287935)
If I were to use 14/4, wouldn't I just use 1 14/4 and a 14/2?

The 14/4 cable would be the 4 travelers (with the white wire repurposed)
The 14/2 cable would be neutral and return switched power

14/4 is not that easy to find.
It wouldn't be code since neutral and hots are not in the same cable/raceway.

Stubbie 01-06-2014 10:55 AM

Why aren't we just using one conductor in a 14/3 to carry constant power to a 3 way at the sw2 location and the other 14/3 to carry the neutral to the sw2 location? Then you can connect a fixture 14/2 to a top 3 way and a fixture 14/2 to a bottom 3 way.

dgfit 01-06-2014 11:21 AM

If you draw out all of the configurations discussed and tag each conductor you will find the configuration I propose at the start uses fewer cables than all the others discussed. That is not my only consideration and I may still run an extra cable for the sake of simplicity.

The key items not considered in several of the other posts:

1 - there are two three way switches in each box
2 - the route from the top switch to the bottom light runs past the bottom box.

dgfit 01-06-2014 11:23 AM

Quote:

Originally Posted by joed
14/4 is not that easy to find. It wouldn't be code since neutral and hots are not in the same cable/raceway.

Wouldn't I have the same problem with my original configuration - the neutral for two travelers would be in a separate cable. That might be the kicker for running an additional cable from the top switch to the bottom light.


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