E-Stops and Circuit breakers

Hey all,
I need some help on a couple of things first off (E Stops)
Is it safe to use an ordinary relay as an estop relay(mcr)? If so what is the advantage of using specialized relay like an ab guardmaster relay? If an ordinary relay will not work
what specs does the relay have to have to be considered
an ESTop relay

(secondly Circuit breakers
Here is an example of what i am trying to do
460 to 120vac control transformer 2kva
My wire size on my 120vac side is 12awg

Hot*****CB***********Control panel lighting*****neutral
Hot
Hot*****CB***********PLC power supply***********neutral

Ok so my question is Would I size my circuit breaker to the ampacity of the wire (nec Tables) If not what should I size it to?

Size the circuit breaker to the lowest current capacity component.

For example, you may have a wire that can carry 15 amps connected to a 10 relay contact.

THIS SITE contains a lot of useful information in a quick format. I would say, go through the sections under Man-Machine Safeguarding Requirements & Techniques then think about your question about ordinary relays as an E-Stop relay again.

please refer to
http://www.ab.com/en/epub/catalogs/12762/2181376/2416247/1239758/1734544/tab2.html

If I am using the 1746-p2 power supply My CB would have to be rated at 1A right? 110VA/120vac=.916amps


http://www.ab.com/en/epub/catalogs/12762/2181376/1239781/1670480/1681260/tab7.html

I would have to use a CB rated at 1A for the panelview 1000 color display
70VA/120=.583A

Would this be correct?

estop

Great website Bernie,
exactly what I was needing.
Also what needs to be dropped out once an estop is pressed
I was going to keep power up through my input devices to the plc when the estop is pressed and drop power going to my output card.
Good/Bad Idea? No movement will be happen once the Estop relay is not energized.

That is our method for the E-Stop. Just be sure that suddenly dropping power doesn't create some additional hazard (an air or electrically supported device falling). If so, that must be addressed also.

Sorry - didn't read your whole reply first.