# Grounding 3-wire subpanel



## nuclianba (Sep 28, 2017)

Replacing an old 60-amp Federal Pacific subpanel in a client home. Main drop is to a new (as of a few months back apparently, looks brand new) 200A service on a detached garage. Feed from main panel to this sub is 3-wire/no ground. I tried to pull the wires out of the conduit so I could feed back through with a new ground, but they wont budge...may be too many underground twists/turns.

The main panel on the detached garage is grounded to a rod, and then there is also an exposed ground wire from the rod running to the house that is bonded to the water main at its point of entry in to the house. That ground wire runs within a few feet of the sub-panel. I'm thinking I will run a ground wire from the sub-panel to the ground wire from the main panel and splice? Anyone see an issue here?


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## backstay (Feb 3, 2011)

So they ran a ground from the garage, to the house to hit the water line. But didn't bring that to the panel in the house? And so, the house panel has no GES, it's just bonded to the neutral?


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## nuclianba (Sep 28, 2017)

backstay said:


> So they ran a ground from the garage, to the house to hit the water line. But didn't bring that to the panel in the house? And so, the house panel has no GES, it's just bonded to the neutral?


Correct...the sub in the house was a Federal Pacific stablok panel, looks to be 70s vintage, only has a neutral bus, no ground bus. Wiring to branch circuits is cloth covered with no ground, all outlets are 2 prong. Boxes are tied together and to the subpanel box, which is tied to the neutral bus. Replacing it all with new romex and adding grounds to circuits, bringing all branches up to code, AFCI, etc.  The main service was upgraded by others a few months back when homeowner bought an electric car, needed to up service for the outlet and had it all replaced, was apparently original pull fuse before they upgraded. 

I was also thinking I could use the conduit to establish the ground path back to the main panel...but since it buried I'm not 100% sure it could carry current from a ground fault, and at the main panel they cut the conduit and replaced the last ~3 feet with PVC flexible conduit to feed the new panel, so I would have to redo that to finish the ground path. Since I don't have 100% certainty on the buried portion I was looking for another option that I feel good about....but I'm not sure I can tap in to the bonding wire and use as a ground path back to the main (its 4 AWG) without running afoul of NEC since it essentially adds a subpanel between the bonding point and the main panel on that run.


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## backstay (Feb 3, 2011)

I would use the conduit as my first choice. I would like to see a picture of flexible PVC conduit. Is it schedule 40?


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## nuclianba (Sep 28, 2017)

backstay said:


> I would use the conduit as my first choice. I would like to see a picture of flexible PVC conduit. Is it schedule 40?


kwik flex nonmetallic. See pic...there are 2 conduits because the house has 2 subs.


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## backstay (Feb 3, 2011)

I doubt that is a code complaint install. It's some kind of ugly too. You should check the continuity of the pipe and fix that **** that they put in.


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## nuclianba (Sep 28, 2017)

backstay said:


> I doubt that is a code complaint install. It's some kind of ugly too. You should check the continuity of the pipe and fix that **** that they put in.


Alright thanks for the advice. I'm going to replace the kwikflex with rigid and use that as my ground path. Conduit has continuity from both ends, so it looks good there.

As for that bonding wire: I pulled on it a bit to see where it runs and they literally just ran it on the ground next to the sidewalk from the garage to the house, and let the lawn overgrow the wire...its ugly and not exactly out of the way...I could see a lawnmower getting entangled or something. I'd like to clean it up if I can. I'm thinking I would cut the wire at the main panel (leaving wire between box and ground rod) and then at the house connect the bonding wire to the ground bus in the new subpanel (note: at its other end, the wire is bonded to the water service and then to another ground rod). Since these panels are on separate structures, and there is no plumbing in/to the garage, my read is that 250.104(A)(3) allows me to terminate the bonding wire to the ground bus in the subpanel...but would appreciate any input if you disagree. I don't have a lot of experience with multi-structure electrical, I usually just work on stuff in a single building envelope, so this is all new to me.


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