Suplemental Grounding to Electronic Equipment

[Kerekes2000]

My peers have told me that it is legal in the eyes of the NEC to run a secondary ground from a grounding electrode to the ground bus in the back of a electronic test station provided the grounding electrode is part of the grounding electrode system and that the supply cord feeding this test station has a legitmate equipment grounding conductor properly installed.

The customer says they require an earth ground to properly run their tests (possibly a noise issue).

I am concerned that if there is an internal short circuit with-in the test set that the fault current will not find it's way back to XO in order to trip the overcurrent device.

If it is legal what installation methods are approved. What size conductors to use and how can the conductors be ran, inside of conduit etc. Should I be concerned with any limitations to the length of this secondary ground?

Thanks in advance for your help on this subject!

 

[stud696981]

Re: Suplemental Grounding to Electronic Equipment

As long as your ground bus and grounding electrode are bonded back to the main grounding electrode system, you should be fine.

If I had to do this without any plans, I would install a #6 wire from the ground bus/strip to a ground rod outside the building that was close to the bus bar and then continue on with the #6 wire and attach it to the building grounding electrode system.

 

[petersonra]

Re: Suplemental Grounding to Electronic Equipment

The current path is from a hot leg of the xfmr to the equipment and than back to X0. The BC protection is on the hot side, not the X0 side. So no matter where the current were to go, if excess current flow occured the OCPD would see it.