Line isolation monitors

[brother]

Just trying to clear up my understanding of the line isolation monitors and isolation transformers (NEC 517).

Ive seen some hospitals that had BOTH grounded and ungrounded systems in operating rooms at the same time, (why i dont know) .
But my question is if the frame/box of a isolation receptacle/system is touch/energized FROM another source should not the isolation alarm sound?? i KNOW it monitors the 2 conductors from the transformer but i thought it also monitor the ground for any current leakage from the secondary /load side.

If not, there appears to a potential danger in the OR where they have the 'grounded system' beside an 'ungrounded' system that can be energized.

 

[ike5547]

I'm far from an expert on these systems, but it seems like it wound be okay to bond the "frame/box" etc. of 517 isolation systems to the equipment grounds of other systems as long as the isolated system itself remains ungrounded

 

[ike5547]

P.S. I'm not advocating this, I'm interested in the answer.

 

[iwire]

All the normal grounding requirements apply to the receptacles supplied from an isolated system.

The only substantial difference is the fact the power supply is not bonded to ground.

 

[iwire]

I'm far from an expert on these systems, but it seems like it wound be okay to bond the "frame/box" etc. of 517 isolation systems to the equipment grounds of other systems as long as the isolated system itself remains ungrounded

I agree, that is my understanding of the rules.

 

[brian john]

But my question is if the frame/box of a isolation receptacle/system is touch/energized FROM another source should not the isolation alarm sound?? i KNOW it monitors the 2 conductors from the transformer but i thought it also monitor the ground for any current leakage from the secondary /load side.

Ground wise both systems should be common, it is pretty much impossible for them not to be, with all the piping systems, metal studs, both systems from from the same source, (Isolation system primary originates from the same source as the non-ISO system.

As for the ISO system touching the non-ISO system if there is a short in the branch circuit wiring of the non-ISO system, the non-ISO system branch circuit OCP should operate. (IS THIS WHAT YOU ARE ASKING?)