120v Relay

I am using a IDEC PLC and have been asked to send a 120v signal to a motor starter. The information I have reviewed shows that I can use the PLC relay for a 120v option and was wondering what the standard is for which side of teh 120v to break. I am assuming I would want to break the line side that way I am assured that the power is always off unless initiated by the PLC.

I am assuming I would want to break the line side that way I am assured that the power is always off unless initiated by the PLC.

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Yes, put your control on the line sdie. The "neutral" side of many motor starters (with 120 volt controls) is wired to the overload relay contacts, so that is not a good place for additional control contacts.

it will "work" either way, but the correct way is to break the "hot" leg. Its much safer to break the hot leg before it goes all over the world and halfway back.

This is how residential light switches should be installed also. If you have a piece of equipment grounded to the case and only break the neutral leg, you can get a pretty nice shock if you touch equipment, even if the switch is off. This just reminds me of my grandmothers refrigerator that was plugged up backwards and would shock the **** out of you if you touched the sink and the door handle at the same time.

Do you guys have a good rule of thumb for wire color?
I have been using blue for the 24+ and white for the 24-. should I following the same rule for thumb for the signal wires? what about 0v? Just looking for a good industry standard.

I would use grey for the 24 vdc common, since white is usually 120 vac neutral.

Almost everywhere i have worked around here has a big rats nest full of wires of all colors wirenutted together, so the wire my change colors 5 times before it gets to where its going. The closest you get to consistence is some people use Brown/Orange/Yellow for 3phase around here because "BOY" is easy to remember.

As far is how its SUPPOSED to be done, 24VDC+ is supposed to be blue, 24VDC- is Blue with white stripe. Yellow for external voltage sources, yellow with blue stripe for external 24VDC+. Just going by memory on this, so someone else can probably correct me on this.

I believe NEMA has all the codes outlined in the NEC somewhere. Or ask anyone in Automotive, they are usually very familiar with the code.