For years the neutral requirement of smart switches have always been a huge challenge since most switches, specially in our country, does not have neutral (lights are wired in series method).
I'm amazed that there are smart switches now that does not require neutral (LIVE ONLY switches) and I have here one 2-gang LIVE ONLY smart switch from KONKE that's been working great for over a month now.
I know the neutral requirement of the old switches are means to power the smart switch. But w/ these LIVE ONLY switches, how are they powered?
I'm not an electrician but I understand that any device needs to complete a circuit w/ the power source in order for get powered, hence switches do nothing but INTERRUPT this circuit to cut the power from the bulb.
In the above diagram, that's how our switches are wired up and I simply replaced that manual switch w/ the LIVE ONLY smart switch and boom, it works!
How the heck can the switch get power if it doesnt complete the circuit for the light bulb, thereby also cutting itself off from a completed circuit as well.
Furthermore, I'm designing a new house for a client, and I was wondering if it's now ok to recommend and rely on these LIVE ONLY SMART SWITCHES . Wiring all the switches w/ a neutral line adds cost to the project and I'd like to save my client $$$ by not requiring a neutral line in the switch boxes anymore.
But these LIVE ONLY smart switches are new territory for me and I'm worried this may be a problem in the future.
The ones I have seen allow a small amount of current flow when off. This can be a problem if your bulb has very low current requirements - such as LED bulbs. They may flicker or remain on at a very low level.
Non-Neutral ("LIVE ONLY") smart switches typically leak a small amount of electrical current through the lighting fixture. This is just enough power to allow the Smart Circuit of the switch to stay powered on, but not enough to illuminate the light fixture itself.
I would recommend running a neutral to every switch. Live only switches work as described by @Eric.C.Miller and @ogiewon. As a consequence, some bulbs (especially LED bulbs) can light up when a live only smart switch is used. There are ways around this - for example Aeotec and Lutron make load capacitors that are wired across the load.
I also would not recommend using a live only switch to control a motor load.
I'm not an expert in this area by any means but I'm pretty sure the national electric code requires neutral in every switch box anyway. At least in the US.
Again, to save costs, instead of having to run 2 wires from the switch box to the light bulb, it'd be cheaper to still do a traditional series connection w/ the Bulb, but the switch box is supplied with a neutral just for the smart switch. This would also be a good retrofit strategy for those w/o neutral in their switch boxes - just find a way to line a neutral into the switch instead of rewiring the whole circuit
The technology of powering smart switches by leaking some current through the load isn't new. That's how all X10 light switches worked and they go back almost fifty years.
A neutral wire is part of a specific electrical circuit. When the breaker is turned off for that particular circuit, one should be able to depend on the fact that no current could still be flowing that circuit’s HOT and NEUTRAL wires. This makes it safe to work on that circuit’s electrical boxes and light fixtures.
Thus, it makes the most sense to bring Hot(Line)/Neutral/Ground into the switch box, and then Load/Neutral/Ground to the light fixture, as shown above in your second picture.
Neutral wires should not be shared amongst multiple electrical circuits, as the total current may exceed the rating for a shared Neutral wire, resulting in a risk of fire. The circuit breakers would not detect the overloaded shared Neutral, as they only monitor the current in their own HOT(Line) wires.
In general, it is always best to hire a licensed electrician to help design/install wiring and circuit breakers, in compliance with your local electrical codes/laws.
I will have to refer back to my original advice above...
I am just not familiar enough with your local electrical codes/requirements/laws to comment on the image above. In general, circuits just are not this simple, as most circuit breakers service multiple outlets and/or light fixtures.
Purely from a simplistic drawing perspective, the following would appear to use less wiring and all wiring is routed along a single path. Thus, lower installation costs.
I've been staying out of this since your diagram shows 220V and you are apparently in another country. I wouldn't even hazard a guess about that.
If you were certain that the neutrals were on the same circuit and we were talking about wiring in the U.S., I might would be briefly tempted to do that. There's no reason that would be unsafe. However, it might prove to be puzzling to the next electrician that is working on your wiring years from now. It is best not to astonish future electricians and plumbers with your decisions today.
You asked the question above about whether something would work, but also asked if it was a bad idea. Good that you are thinking like that. There are a bunch of examples why "Will it work?" is a poor and dangerous way to decide whether a given wiring should be done.
You are going to save a penny on wiring but will pay a nickel on labour. There's no reason to do it that way unless you are wiring a Google stadium size server room.
