Safety AUX contactors & Safety Relay

[Ruhstko]

Hello colleagues! I decided to ask for advice, I hope someone has already studied the issue.

I'll try to formulate more correctly. There is such a thing - Safety Aux Contactor - for example, the WEG series CAWBS or Bulletin 700S by Rockwell.

There are also well-known safety relays. Is it possible to expand the contacts of the safety relay by connecting the Safety Aux Contactor? If we`ll switch its coil through the contacts of the safety relay.
Either it is unacceptable, because it is outside the rules and standards?

 

[kolyur]

What you are suggesting is done quite frequently. Safety contactors are nothing more than regular contactors with force-guided contacts. (Apparently the red and yellow colorings for plastic are very expensive.) Since they don't have any logic of their own, they are driven from contacts of master safety relays. Just be sure to use the NC contacts for EDM feedback if your application calls for it.

 

[Old No. 7]

Page 12 in the following manual shows exactly what you describe.

https://literature.rockwellautomation.com/idc/groups/literature/documents/td/700-td552_-en-p.pdf

 

[PreLC]

AB has these expansion relays: https://www.rockwellautomation.com/...ty-relays/specialty-safety-relays/msr132.html

Which are supposed to expand the MCR output to other output circuits, as if they were connected directly to the MCR.

I'm not sure how much cascading is allowed though, I'm guessing there has to be a reasonable limit, as each cascade probably adds a time delay when the output switches, maybe someone else on the forum can elaborate.

 

[g.mccormick]

I have used a pilz 774150 expansion module several times. Gives 8 NO safety outputs.

 

[Ruhstko]

UPD. In general, as I thought. Then the question is different. I have, for example, a Pilz relay with a bunch of outputs. How legal is it to put an external considered safety relay instead of built-in outputs?

 

[jholm90]

UPD. In general, as I thought. Then the question is different. I have, for example, a Pilz relay with a bunch of outputs. How legal is it to put an external considered safety relay instead of built-in outputs?

It depends on what will turn on the external safety relay. If it is being used to expand an existing one, then tying in the EDM N/C contacts is fine. If it is being turned on by something else then jt needs an assessment to make sure that is being implemented in the correct fashion.