[denny3992]

After inspecting existing panels at work, i found improperly installed ig panels... Heres the jist

Each floor of a 16 flr bldg has buss duct feeding a 480 panel then to a 120/208 transf. They have 2'panels coming off the transf.
1 (ig), 1 not

The ig panel is fed in greenfield, with 4-#2thhns 3-hots and neutral
And a #6 from thr grnd lug in transf that originates from 480v grnd and bldg steel.

The grnd in the (ig) panel is isolated from backbox.
And they have a green jumper to the box from the neutral bar.

And the xo is bonded to grnd in xfrmr.

Im baffled as to what they were trying to do.

And how to suggest to fix.

Any help?

 

[cuba_pete]

Poor IG...no grounding conductor

After inspecting existing panels at work, i found improperly installed ig panels... Heres the jist

Each floor of a 16 flr bldg has buss duct feeding a 480 panel then to a 120/208 transf. They have 2'panels coming off the transf.
1 (ig), 1 not

The ig panel is fed in greenfield, with 4-#2thhns 3-hots and neutral
And a #6 from thr grnd lug in transf that originates from 480v grnd and bldg steel.

The grnd in the (ig) panel is isolated from backbox.
And they have a green jumper to the box from the neutral bar.

And the xo is bonded to grnd in xfrmr.

Im baffled as to what they were trying to do.

And how to suggest to fix.

Any help?

That's crazy...the enclosure is at neutral potential. The system bonding jumper is made at the source or at the first disconnecting means, not both. (X0 in this case, the source). This presents the potential for objectionable current. There is no grounding conductor at your panel.

Remove the green jumper from the box to the neutral. I'd check to see how they wired the non-IG panel. Sounds like a hot mess.

The grounding bar can be used for building ground or IG. If it is used for building ground it must be bonded to the enclosure. If you make the #6 the IG and isolate it and the ground bar from the enclosure you will need to run another grounding conductor and bond that to the enclosure. Either way, the enclosure needs to be bonded to building ground.

The IG is allowed to pass through back to the xfmr. If it's bonded at the ground bar, and the #6 is bonded at the ground bar, and the ground bar is bonded to the enclosure, then it's not really an IG...it's the EGC. That's a waste of the extra ground bar and insulators.

How are the branches wired? You may have more issues if the receptacles/enclosures are not wired correctly.

This is one of those examples of how not to install an IG...whether needed or not is another question.

 

[Meadow]

Who knows, could be anything.