MCC Feeder Cable Grounding

[mobojaba]

Being new to the electrical distribution industry, I was stumped by a situation found at one of our sites.

We have a 3 phase 600/347V bus fed by a 4 wire feeder cable. We have several loads off the bus being 600V MCCs (no 347V loads) and 600/347V Panelboards.

In one of the MCCs, there are two parallel feeder cables that are 3C with a cable ground wire (not a neutral). The MCC is also bonded to our system ground through a separate bonding cable.

Do the feeder cable ground wires need to be terminated on both ends, or just on the feeder side?

I'm following CEC standards.

Thank you in advance

 

[davidbeach]

Both ends.

 

[mobojaba]

Why is that? Would it possibly establish ground loop currents?

 

[dpc]

Why do you think the ground wire is there? The main purpose is to provide a fault return path and to maintain the same ground potential at each end.

 

[mobojaba]

Thank you for the advice.

The original contractor (2 years ago), installed this and turned it over as inspected and commissioned. They also cut the grounding cables too short to reach the ground bar inside the MCC, so they are currently hanging free in the wireway.

We had an electrician in to do extend the grounding cables and terminate them onto the ground bar, but he objected claiming that it could cause a ground loop current and could damage a VFD in the MCC.

It didn't make any sense to me, but I wanted to get some feedback before I advise any action.

Is there any situation that you wouldn't terminate this wire?

 

[dpc]

Not terminating the ground wire at the source is a major NEC violation - I assume it is in Canada as well.

Having said that, if these circuit are in steel conduit, it can meet code requirements for an equipment grounding conductor if approved fittings are used. This is not as good as ground wire inside the conduit, but it would meet Code (again, the NEC).