Steel Building Sub Panel Grounding and Bonding

[Gangly]

I installed a 100 amp sub panel in my shop (steel building on a concrete slab) that is fed by copper 6 AWG UF from a 60 amp 2 pole breaker in my main panel that is attached to my house.

I mounted the subpanel in the detached steel building to a 3/4" x 4' x 4' plywood board, and screwed the plywood to the steel frame of the building, so the subpanel is not bonded to the steel building at this time. I installed a separate bus bar in the panel for the grounding so that the ground was not bonded to the nuetral in the sub panel. I then hammered an 8' ground rod immediately adjacent to the building and sub panel, and ran a 6 AWG copper cable from a the ground bus bar in the subpanel to the grounding rod.

The steel structure is not attached to the installed grounding rod, and not bonded with the sub panel.

My questions are these:
Since the sub panel has a dedicated 6 AWG cable running from the subpanel to the immediately adjacent grounding rod, can I just run a bonding cable from the steel frame of the building to the sub panel, or do I need to also install a separate cable that runs from the steel frame directly to the grounding rod? Should I do both?

 

[wyliesdiesels]

code requires 2 rods unless you can prove 25ohms to earth

i would bond the steel structure to the ground bar in the panel

Is the #6 UF 4-wire (2 hots neutral and ground)?

 

[Gangly]

code requires 2 rods unless you can prove 25ohms to earth

i would bond the steel structure to the ground bar in the panel

Is the #6 UF 4-wire (2 hots neutral and ground)?

Yes, it is.

Right now I have a newly installed single ground rod for the steel building, and a separate ground rod at the main panel at the house. So that I am understanding you correctly, I will most likely need need a third ground rod for a total of two at the steel building and one at the house?

When I install the second ground rod at the building, do I connect a 6 AWG jumper between the two rods at the steel building, or do I need to run a second 6 AWG conductor from the sub panel to the second ground rod?

Thank for your timely response and knowledge sharing, I appreciate it.

 

[wyliesdiesels]

you need 2 rods per building. so you need to add 2 more- one per building. you can connect the second rod to the first but i prefer to just use one piece of wire looping thru the connector on the first rod

 

[Gangly]

Makes sense.
Thank you for your responses, I appreciate them.

 

[PCustoms]

you need 2 rods per building.

Doesn't that depend on when his house was built?


That said, spend the $20 and add the second one at the house

 

[Chuckster in NJ]

Grounding and bonding is the most important thing on an electrical system……… Never cheat on this!

I inspected a service change years ago and the "licensed electrical contractor" argued with me (for about 30 minutes) about using an existing ground rod and wire.…… He also said there were two rods, so I told him to go outside and grab the #6 wire from the panel to the rod (to check the integrity of the 20 year old wire and rod connections) and when he proceeded to pull it out of the earth the wire wasn’t even connected to the rod.…….. He charged the owner $175 extra because I was a ***** who made up "fake" code violations.
I always allowed using an existing rods if they could prove the 25 ohms or less in front of me so instead of waiting for me on the job MOST contractors would spend the money and do it right the first time and use new wire and two rods…….. I always preached about proper bonding and grounding in code update classes.

 

[wyliesdiesels]

Doesn't that depend on when his house was built?


That said, spend the $20 and add the second one at the house

2 rods have been required for a long time.

 

[PCustoms]

2 rods have been required for a long time.

Any idea how long?

Current house certainly wasn't code compliant in many ways, but had 1 tied to the meter pan per PoCo instructions. Last house had 1 as well IIRC and I thought was to code at the time

 

[mm08822]

Grounding and bonding is the most important thing on an electrical system……… Never cheat on this!

I inspected a service change years ago and the "licensed electrical contractor" argued with me (for about 30 minutes) about using an existing ground rod and wire.…… He also said there were two rods, so I told him to go outside and grab the #6 wire from the panel to the rod (to check the integrity of the 20 year old wire and rod connections) and when he proceeded to pull it out of the earth the wire wasn’t even connected to the rod.…….. He charged the owner $175 extra because I was a ***** who made up "fake" code violations.
I always allowed using an existing rods if they could prove the 25 ohms or less in front of me so instead of waiting for me on the job MOST contractors would spend the money and do it right the first time and use new wire and two rods…….. I always preached about proper bonding and grounding in code update classes.

Since he's doing a service upgrade, expecting to use the existing rod and conductor, that all has to be in proper order to leverage it. Otherwise, yer adding new hardware in place of the old.

 

[wyliesdiesels]

Any idea how long?

Current house certainly wasn't code compliant in many ways, but had 1 tied to the meter pan per PoCo instructions. Last house had 1 as well IIRC and I thought was to code at the time

not sure. id have to dig thru all the editions of the NEC to check... dont have time right now