2 vs 3-wire switches

Other Devices & Integrations Lighting & Load Control
#1

So,

Can anyone here tell me why they build 3-wire switches? If WD can pull the power for the radio from the load, why can’t GE do it? And, how does WD do it? Are they using the Ground as the neutral (and why doesn’t it violate code)?

Or, do they have small nuclear reactors in the switches… ???

Thanks…

#2

@haveitall,

Welcome!

Ground is for safety. Certain loads (say, something other than an incandescent light) don’t like to be on just a little bit, some of the time. For those loads you want to power the electronics inside the switch (i.e. the Z-Wave radio etc.) separately; so it needs its own neutral, rather than the load’s neutral.

#3

If you have 3 wires then the module can be powered without putting any power through the bulb.

It also means that if the bulb expires the module won’t lose power and your z-wave network won’t be affected.

#4

[quote=“gilesjuk, post:3, topic:169226”]If you have 3 wires then the module can be powered without putting any power through the bulb.

It also means that if the bulb expires the module won’t lose power and your z-wave network won’t be affected.[/quote]

And therefore you can dim to zero current.

Modern incandescent replacement sometimes get enough power from the ‘trickle’ let through tby 2wire switches to actually stay lit. Some flourescents and LED’s will never turn off with 2wire switches.

#5

Ah, there is the rub. I didn’t know that they trickled the current when it was off.

Sounds like the 3 wire is the way to go where I have the wiring.

#6

The very expensive MK Astral switches are three wire but state you can run them with two wires if you’re not using energy saving bulbs.

I’m using two wire with 230v halogen bulbs, they still save some energy but are comparable to incandescent bulbs in use.