Grounding

[billnv]

WE HAVE THE FOLLWING ITEMS AT AN INSTALLATION.
1) 1600 AMP 120/208 V BOLTED PRESSURE SWITCH
2) 1600 AMP AUTO TRANSFER SWITCH 4-POLE
3) 750 KW GEN-SET
4) 1600 AMP DISTRIBUTION SECTION
THERE ARE (4) 3.5" PVC CONDUITS RUN BETWEEN EACH OF THESE ITEMS. IN THE FIRST CONDUIT THERE ARE (4) # 500MCM AND (1) # 4/0 GROUND WIRE WITH THE #500MCM CONNECTED TO 'A' PHASE. AND THE #4/0 CONNECTED TO THE GROUND BUS. LIKEWISE WITH'C','B', AND NEUTRAL.
THE NEUTRAL IS GROUNDED IN THE BOLTED PRESSURE SWITCH TO A GROUND TRIANGLE GRID, BUILDING STEEL,BUILDING WATER SERVICE, AND A SUPPLEMENTARY CHEMICAL WELL GROUND.
IF AN AMP METER (DIGITAL OR ANALOG) READING IS TAKEN IN THE BOLTED PRESSURE SWITCH, ATS, OR DISTRIBUTION SECTION ON THE EQUIPMENT GROUNDING OCNDUCTOR THERE IS A 80-100 AMP CURRENT. IF THE GROUND WIRES IN THE A,B,C, CONDUITS ARE DISCONNECTED THERE IS A CURRENT OF 17-18 AMPS ON THE GROUND WIRE REMAINING IN THE NEUTRAL CONDUIT.
THE SUB PANELS HAVE ALL BEEN CHECKED FOR CROSSED NEUTRALS AND GROUNDS. THERE IS NO MAGNETIC MATERIAL THAT THE PVC CONDUITS PASS THROUGH.
THE BUILDING LOAD IS APPROXIMATELY 420 AMPS PER PHASE.

AGAIN, WE WOULD LIKE ANY ADDITIONAL COMMENTS FOR OUR QUESTION AS TO WHERE THE CURRENT IS COMING FROM?

 

[dereckbc]

Re: Grounding

How is the generator configured, SDS or non SDS? Is the ATS 3-pole or 4-pole? It is quite possible you have a second bond on the Xo in the generator if you have a 3-pole ATS (non SDS). Otherwise hard to answer your question with limited info.

Edit: After reading your post again, I have a question. Are you saying you have all the "A" phases in one conduit, "B" in another, and "C" in another? If so, your problem starts there.

[ April 26, 2004, 04:01 PM: Message edited by: dereckbc ]

 

[charlie b]

Re: Grounding

I received the following update from billnv:

Something that I left out of my original description of the 1600 amp installation is that the bolted pressure switch is fused at 1500 amp panel. The circuit breaker on the gen set is adjusted to 1500 amps. Could you please reply to these questions? Your answers are appreciated.
1) is the installation code compliant?
2) could the (4) sets of 500 mcm be fused at 1600 amps if calculated according to 310.15(6)(c)?

In view of the new information being added to the original question, I am returning it to active status.

[ April 30, 2004, 11:31 AM: Message edited by: charlie b ]