Grounding

[SMB]

I have a shelter with electronic racks. One end of the shelter has a main grounding plate (MGP), the other end a secondary grounding plate (SGP) with a bare 4/0 connecting them routed through and connected to a metal cable tray. An equipment ground is connected from the MGP through the cable tray to each rack also connected to the SGP thus creating an apparant ground loop. Should one of these grounds be disconnected from the SGP thus eliminating the loop? is this covered somewhere in NEC 250?

Any insight will be greatly appreciated.

 

[brian john]

I have a shelter with electronic racks. One end of the shelter has a main grounding plate (MGP), the other end a secondary grounding plate (SGP) with a bare 4/0 connecting them routed through and connected to a metal cable tray. An equipment ground is connected from the MGP through the cable tray to each rack also connected to the SGP thus creating an apparant ground loop. Should one of these grounds be disconnected from the SGP thus eliminating the loop? is this covered somewhere in NEC 250?

Any insight will be greatly appreciated.

GROUND LOOP?

1. Can you measure any current?
2. Are there any issues?
3. What is the concern?

 

[ceb58]

I have a shelter with electronic racks. One end of the shelter has a main grounding plate (MGP), the other end a secondary grounding plate (SGP) with a bare 4/0 connecting them routed through and connected to a metal cable tray. An equipment ground is connected from the MGP through the cable tray to each rack also connected to the SGP thus creating an apparant ground loop. Should one of these grounds be disconnected from the SGP thus eliminating the loop? is this covered somewhere in NEC 250?

Any insight will be greatly appreciated.

Is a grounding ring (from out side) connected to the MGP and SGP to form a grounding loop? The communications site I deal with have one MGP on the inside of the building which is bonded to a MGP on the outside, this is where the grounding wires from the in-ground ring around the tower lands. Inside the building we have a halo around the inside of the room which originates from the inside MGP, all metal frames, cable trays,conduits and racks are tied to this halo. We do leave a air gap in the halo (6"). This is done so that when there is a strike the lightning cannot make 500 laps around the room before dissipating:grin: