supplemental ground rod

[wireday]

I have a 480 piece of equipment located in a indoor wet area, It was suggested by others that I should install a ground rod at the equipment. I have seen this done both inside and outdoors, the equipment has EGC from the feed circuit. does this offer further protection?

 

[infinity]

Since you already have the proper size EGC IMO the ground rod would be a complete waste of time and money.

 

[tom baker]

Who suggested this? Is this for electrical safety from a shock?

 

[retirede]

When I started my first job out of school as a plant engineer, the factory I worked in had a ground rod at every machine tool. I asked why and was told “we always do that.” I didn’t think it was in my interest to challenge the senior guy at that point, but I knew it was a waste.

 

[petersonra]

I have a 480 piece of equipment located in a indoor wet area, It was suggested by others that I should install a ground rod at the equipment. I have seen this done both inside and outdoors, the equipment has EGC from the feed circuit. does this offer further protection?

For the most part, all it offers is a commission to the guy selling ground rods, and maybe (I said maybe) a path for lightning to get into your equipment.

 

[wireday]

Who suggested this? Is this for electrical safety from a shock?

Yes that was there point

 

[HEYDOG]

Yes that was there point

The equipment grounding conductor is there to clear the overcurrent device in case of ground fault. The ground rod is not going to clear the overcurrent device!

 

[retirede]

Yes that was there point

They are wrong.

 

[tom baker]

Yes that was there point

Ok do the math. At 25 ohms, which is typically low for a ground rod, at 277 volts, in the event of a line to case fault, how much current will that be? Will that open the OCPD?
Or even at 480 V?
The NEC considers this ground rod to be a supplemental rod, it’s not required, so the GE rules do not apply - ie minimum size of GE conductor, etc

 

[tom baker]

At 480V, due to the IR squared law, there is much more heat from a ground fault. Instead of a worthless ground rod, make sure all your joints are tight, use penetrox e on all joints, threads, use bonding bushings. Although 250.118 allows use of metal raceways as an EGC, pull a wire type EGC.