I want to install the GE Smart Dimmer switch (#12729) in a 3-way circuit to control my room lights. The instructions say I need to also install a GE Add-on switch for “Multi-Switch 3-way or 4-way installations”. There are 5-switches in this circuit that control the room lights. I’m installing the Dimmer on the load end. My question is do I have to replace every switch in the circuit with an add-on switch or only one? If I only need one, must it be The first switch in the circuit (the line end)?
You have to replace every switch. Networked switches are wired a little differently than non-networked switches.
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You will need to replace all the switches in the circuit with the smart 3 way or add on switches. Where you put the smart 3 way switch will depend on where the line voltage is coming from (not load).
I’ve replaced several groups of 3-way switches in my home with the GE versions. Most have been easy and one of them was a PITA. To answer your question a little further than others above; yes you do need to replace all the switches unless you remove the 3-way toggle feature via the travelers. Normal 3-way switches have 3 wires attached to it (ignoring the ground as a true wire), the common wire (should be the black wire in most cases) and 2 traveler wires. Think of the standard 3-way switch as a flip flop gate between the common and traveler 1 or traveler 2. Depending on the position of the main switch or the other switch in the line determines which leg of that flip flop gate is hot.
Where the GE ones differ is that the traveler is never hot from the black wire. That’s reinforced with them putting a sticker over the traveler hole that says “NO 120V”. This is because the GE switch uses the neutral wire as a trigger, hence why they require a white neutral wire to hookup. On the other end of the switch, lets say the dummy switch there are only 2 wires connected (again excluding the ground as a real wire) thats the neutral and the red traveler wire. That red wire is essentially just a signal wire to the main or load switch telling it to turn on or off.
There are a number of different ways to wire up 3-way and more switches and depending on the setup of your wire pulls and lights. My home is almost 30 years old and I’ve replaced all but one of the 3-ways in my home and everyone was different. This most recent one I did on Sunday was the worst yet and required me to completely rewire the 3 gang box the switch was in, the box in the ceiling the light was attached to and the single gang “dummy” at the end of the line. I’m not expert but I doubt the way it was wired was up to code even 30 years ago. In the triple gang box they had some hot and commons tied together and neutral/hot reversed in addition to one of the red travelers going direct to a light in the ceiling and the hot/common reversed again in the dummy, it was a mess for sure. My point in this for anyone doing this later on is to 1 carefully document the as-is wire situation before unhooking anything. Then 2 do not hook everything to the new GE switch ie the red traveler without testing that it works. I have always test the operation of the switches before closing everything up and if I had assumed it was all right the red traveler on the main switch would have been hot the way it was wired up.
I’m by no means an electrician, just dozens of years of personal experience so if someone more experienced wants to elaborate or correct on any of this please feel free by all means.
Thanks all for the help. Just finished wiring the switches and some work but others don’t. After doing more research I found this information about the Smart Dimmer - “May be used… with up to two GE Add-on switches in 3-way or 4-way wiring configurations”. Wish I saw that before installing the 4 add-on switches. Does anyone know of another manufacturer that makes a switch that can be used in a 5 switch circuit?
I am using a GE dimmer with 4 add in switches without a problem. I think the limit is in the 4-5 range, not 2.
I would hazard a guess that more work on wiring will be a solution for you…
What is the model number of your smart switch? Also, can you provide a wiring diagram?
Most of my switches are in boxes that have travel wires only- no neutral wires are available. What do I do in that case?
Re-wire 
Seriously - will need to re-wire to get one.
Or go an entirely different route.
Spent the day fishing wires to run neutral to all boxes so all should be good except it still doesn’t work! One travel wire at one box has 110v with the breaker turned off. Time to bring in an electrician.