Inductive prox wiring practice 2

[bentov]

Literature with 2 wire universal voltage inductive proximity sensors shows control power arriving at a relay coil (A1), then a wire (call it B)from A2 out to the prox, returning from the prox to complete the circuit to the neutral conductor. So, wire B, though not technically a neutral, is separated from 120V by the relay coil, limiting the potential fault current.

There's going to be a bunch of these 2 wire circuits, in EMT conduits, tapped at aluminum conduit bodies. Do we need a ground wire, and do we have to figure out how to bond it in the conduit bodies? What color should wire B be? Would this be relatively "intrinsically safe" wiring, or would it be if we changed to 24VAC? Or 24VDC?

 

[roydm]

If you have exposed metal it should be grounded unless you are just talking the barrel of the switch. If you have connections in the conduit fitting it should be grounded for sure.
No it will not be intrinsic safe unless its approved for that and it is supplied by an Intrinsic Safe barrier,

 

[bentov]

roydm, thanks for your reply. I knew these things, I guess, just looking for a bye to save trouble (PITA to terminate bonds in those conduit bodies). What I meant by "relatively" safe was comparatively low shock & fault damage hazard, shouldn't have said "intrinsic" as I know it pertains to hazardous locations with galvanic or zener barriers.

I'm thinking in general of proxes, laser or ultrasonic sensors, pressure transducers, etc. - small, low voltage stuff frequently connected up in conduit bodies & dropped out through nylon strain reliefs. I've seen such things put together without the bond I know is required (for power wiring anyway)in any junction box where a splice is made - just wondered if there's a V or VA threshold below which it's actually code to do it that way. 24VDC PLC I/O wiring & components especially are often very compact, not much room for typical bond termination. Or say, for instance, a remote E-Stop button in its own metal enclosure, connected to a main panel by 50 ft of EMT conduit - ground wire & bond terminal required . . . ?