Supplemental Ground for Air Compressor

[scnkapc]

I have (3) 350-HP Air Compressors where Ingersol Rand requires a supplemental ground rod. They drove a ground rod next to the pad and ran a #4/0 to the frame of the compressor-not the motor. These air compressors are fed with 2 sets of 3 #250 w/#2 ground. I know in the past this has been an issue because the supplemental ground is not connected to the circuit grounding conductor and creates a difference in grounding potential.

Should I make them connect the supplemental grounding conductor to the electrical grounding conductor that is in the main 800 amp disconnect that goes to the motor pecker-head?

 

[infinity]

I have (3) 350-HP Air Compressors where Ingersol Rand requires a supplemental ground rod.

What do the manufacturers instructions say?

I know in the past this has been an issue because the supplemental ground is not connected to the circuit grounding conductor and creates a difference in grounding potential.

From a code perspective you can hook it up anyway you want unless the manufactures instructions as part of the equipment listing tell you otherwise. Here's the code section which has no real requirements:

250.54 Auxiliary Grounding Electrodes.
One or more grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.53(A)(2) Exception, but the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4).

 

[scnkapc]

Thanks

 

[infinity]

Thanks

You're welcome. Many here will argue that the ground rod is useless but you are required to follow the manufacturers instructions. That specific code sections allow you to connect the auxiliary electrode to the EGC but you are not required by the NEC to do so. Is that lug in the photo factory installed on the equipment? If so then it appears that they connected it correctly.

 

[scnkapc]

Is that lug in the photo factory installed on the equipment?

Yes, it came with the grounding lug in the picture.

 

[infinity]

Is that lug in the photo factory installed on the equipment?

Yes, it came with the grounding lug in the picture.

I think that one can reasonably assume that the lug is there for the connection as shown in the photo so it's probably good to go.

 

[scnkapc]

Thanks again.