Hi - I’m doing some rewiring and got to thinking about this. Latest NEC code requires all junction boxes (JBs) to have a neutral in them, but does not require a live. In the case of a two way switch you’ll have both neutral and live in your JB by default. But for a 3 way switch you’re likely to end up without live in one of the JBs. Can smart switches deal with this? To be clear - one of the travelers for the 3 way/4 way would always be hot - but it would toggle between when is hot and which isn’t as the switch gets toggled.
Thank you!
The smart switch must be on a live line wire otherwise once it was turned off the “smart” part of the switch would stop working. In 3/4 way switches - there is only one “main” that is connected to the line and that is where the smart switch must be (also note, not every smart switch is 3/4 way compatible). Different smart switches can handle different configurations on the other switches. Many require a companion switch or some sort of jumper wiring to be done. Innovelli is the only one I’ve seen reliably work with existing dumb switches reliably w/o tweaking. If there is no line coming into the 3 or 4 way box via traveler, then you’ll have to buy a battery powered remote that pairs with the switch (Caseta has one, I’m sure there are others).