Resolving two 3-Way Switches for two separate lights on one Combination Switch

Question

I am now attempting to wire two existing three way toggle switches to a Leviton 5643 three way combination switch for two 3-way lights on the same circuit - Pictures included.
Box 1 is what I term the “main box” because it is next to the remote for the fan.
It is important to know that the fan needs continual power so the remote will work.
We can turn the fan/light on and off with both three way switches located at box 1 and 2
Box 1 holds one three way switch
2 gang Box 2 holds two three way switches
In Box 2 - Switch 1 (left switch) works with the fan/light
In Box 2 - Switch 2 (right switch) works with the foyer light
After much work and testing I found the following.
Box 1 is providing the power to the ceiling fan/light.
Box 2 is providing the power to box 1.
I ran a new wire to the 2 gang Box 2 to handle the recessed lighting.
I will leave the wiring for box 1 as is for the ceiling fan/light.
I will be adding a new 15a Leviton Decora 3-way combination switch to handle the power to and from the ceiling fan/light and foyer light.
TOTALLY LOSING MY MIND NOW!
I attempted to wire things as instructed by the combination three way switch and it tripped the breaker. I un wired everything just to see what is happening and found it odd that I was getting power from the Foyer three way wires when I have everything unconnected.
Below is Box 2 showing all of the unconnected wires except for the neutrals.
This box held two three way toggles. I added a new 14/2 wire for the dimmer.

Below is box 1 with 3-way toggle.

Below is the inside of box 1 showing two wires (one 14/3 and one 14/2).
The 3 way wire goes over to box 2 and the 14/2 wire goes to the ceiling fan/light.

Below shows the old wiring for Box 2

Below shows the old wiring with the two 3 way toggles in place. Not sure why the black wires are wrapped around the two sets of travelers?

Below is the wiring image I used to illustrate my situation. Obviously the wiring shown may not reflect what I have because the box 2 on the right only reflects one 3 way toggle switch.

Two gang box from inside the closet.

ThreePhaseEel · Answer

Check your box fill
Your plan to feed the recessed lighting from and mount its dimmer at the existing two-gang where power comes in is a good one, save for one issue: box fill.  You see, the NEC allocates a given amount of space for wires and devices in boxes to avoid overcrowding and its consequent issues with wire-bending and overheating.  In particular, you have 18 wires in that box, consisting of 12 current carrying wires, 2 wires' worth of grounds (1 for every 4 grounds), and 4 wires' worth of devices (2 wires per gang * 2 gangs).  For 14AWG wire, this yields 36in³, which is a bit more than your average two gang plastic box holds, as those cube out at 32in³.  So, you'll need to check the fill capacity printed on the inside of your existing two-gang box, and replace it with an extra-large box if it comes up short.

Resolving two 3-Way Switches for two separate lights on one Combination Switch

One Answer

Check your box fill

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