Equipment Grounding Question

[SparkOmatix]

I have a few skids with various motors and so forth on each. My question is as follows:

What is best practice with regard to grounding:

Ground each item to the skid and then the skid to the ground grid...

or...

Ground each item to the ground grid itself

What are the advantages/disadvantages for each method?

Thanks in advance for your time and informed answers!

 

[resqcapt19]

The most important connection is the connection of the equipment to the Equipment Grounding Conductor that is run with the power supply. The connection to the grid itself is not a code issue, but a design issue and either method will be fine.

 

[dpc]

I agree with resqcapt - make sure you run a green ground wire with the power circuits (don't rely on the conduit).

If these are small motors, I think supplemental grounding to the skid is probably fine. If these are very large motors, it is not unusual to provide a dedicated stinger to each motor from the grid. But for a ground fault in the motor, almost all of the fault current is going to flow in the equipment ground. All other paths will have a much higher inductive reactance.



David Castor

http://www.cvoes.com

 

[waross]

If this is a petrochemical plant, the API code may require grounding in addition to NEC grounding. As well as the equipment ground conductor, may require a much larger ground conductor from the motor frame to the ground grid.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[automatic2]

On oilfield power skids that we build, in addition to the line group bond, we do an exterior motor frame bond run to a ganged terminal which is mounted securely/electrically to skid frame, which in turn is wired back to service entry bond.

We've queired this requirement from our CSA inspector and they insist on it.