I have a power supply that has only screw terminals for its AC mains input. Currently I'm using a power cord from a computer that I cut the female end off of and attached fork terminals to (live, neutral, and ground). It works fine but now I'd like to add a rocker-type switch to the cord so I don't have to unplug it whenever I turn it off.
Is it better to use a DPST-type switch to simultaneously connect/disconnect the live and neutral wires or is a SPST-type switch fine? If an SPST is ok, does convention and/or code prefer attaching it to the live or neutral wire?
Best Answer
ALWAYS switch the live wire(s). If you only switch the neutral, then the entire circuit becomes live when switched off.
Switching the neutral also can add some safety in case the outlet is wired backwards. It would also allow you to give it 120-0-120 split phase later on (240v total), if it's rated for that.
Do NOT switch the ground, but you probably knew that.
In case you didn't know, neutral is actually the center tap of the utility transformer outside and is (supposed to be) connected to ground (dirt) in the breaker box and nowhere else. This is why it's okay to leave the neutral connected in most cases. However, don't be tempted to use ground to carry current just because it goes to the same place. Neutral is there because the current that it carries causes it to not be ground anymore once it leaves the breaker box.