ground in 120/240V apartment circuit

[lielec11]

I am reviewing drawings for someone who is renovating a 14 story apartment complex. They are rewiring the apartment risers and apartments using existing conduit. Building service is 120/280V, 3-phase and the apartments are single phase. I noticed they are NOT running a ground to the apartment risers or panels, only 3#250 for the risers and 3#8 to the apartments.

Is there a section in the code that mandates grounds be run with a renovation like this? I always run a ground so I haven't ever had to look for this in the code. For what it's worth they are installing new grounded receptacles in the apartments which jumped out at me as well.

Thanks.

 

[ptonsparky]

Properly installed metallic conduit is an EG.

We we usually pull the magic green wire, but it is not necessarily required.

 

[lielec11]

Ok so I would have to confirm the existing conduit is indeed metallic. Assuming it is, they would still need tie in the ground of the receptacle to the metallic conduit via a bonding jumper correct?

 

[kwired]

Ok so I would have to confirm the existing conduit is indeed metallic. Assuming it is, they would still need tie in the ground of the receptacle to the metallic conduit via a bonding jumper correct?

Sometimes yes sometimes no.

If receptacle is mounted securely to a metal box (which is supposed to be bonded) it is considered bonded by the mounting hardware.

If receptacle is not securely mounted to bonded box - it still may not need a wire jumper if it has those metal spring clips that hold the mounting screws to the device - AKA self grounding device.

 

[lielec11]

Sometimes yes sometimes no.

If receptacle is mounted securely to a metal box (which is supposed to be bonded) it is considered bonded by the mounting hardware.

If receptacle is not securely mounted to bonded box - it still may not need a wire jumper if it has those metal spring clips that hold the mounting screws to the device - AKA self grounding device.

And if the back boxes are not metal then we would need bonding wire to receptacle. Seems like a stupid question I know but I'm only going on a set of drawings and have no idea of what's in the field in this case.

I stumbled onto 250.130(C), which seems to cover what my concerns are.

 

[kwired]

And if the back boxes are not metal then we would need bonding wire to receptacle. Seems like a stupid question I know but I'm only going on a set of drawings and have no idea of what's in the field in this case.

I stumbled onto 250.130(C), which seems to cover what my concerns are.

Yes, and you also need an EGC in your wiring method or else there is nothing to bond to.

 

[lielec11]

Yes, and you also need an EGC in your wiring method or else there is nothing to bond to.

So regardless if the conduit is metal or not, the back box needs to be metal or else you can't bond the receptacle. Can't you tie the receptacle ground to a bushing where the conduit enters the box though?

 

[kwired]

So regardless if the conduit is metal or not, the back box needs to be metal or else you can't bond the receptacle. Can't you tie the receptacle ground to a bushing where the conduit enters the box though?

Bottom line is metallic wiring methods need bonded, metal boxes need bonded, EGC on the receptacle needs bonded. If all those components are metal and assembled with tight fitting connections they can be the EGC to pass continuity from one item to the next. If you have non metallic component somewhere in the chain - you need bonding jumper to go around that insulating link. Metal raceway into plastic box - the metal raceway needs bonded, doesn't have to be at this end though. If no EGC is pulled inside that raceway then you somehow have to get a bonding jumper from that raceway to the receptacle - grounding bushing is one option.

 

[lielec11]

Thank you!