Subpanel - Ground

[msi99]

Is there an exception in the NEC 2023 that allows us to retain the existing interior subpanel with only L1, L2, and N conductors, but no ground, on a residential property without requiring an upgrade to the subpanel to include a ground connection when installing a solar system?
The Main panel on the exterior is built per NEC 2023. The subpanel will be fed via the feeders from the main panel. The subpanel will be on the same structure as the main panel.

 

[Eddie702]

Don't understand. You say "main panel on exterior"......."interior subpanel"......"subpanel on same structure as the main panel"

How can the above be true?

Also what type of wiring is feeding the subpanel not to have a ground or is the raceway the ground since it is a feeder.

 

[msi99]

The subpanel is back to back with the main service panel. The subpanel which is located inside the house is being fed via the feedthrough lugs from the Main panel (exterior mounted). The feeders are in flex with only L1, L2 and N.

 

[infinity]

The subpanel is back to back with the main service panel. The subpanel which is located inside the house is being fed via the feedthrough lugs from the Main panel (exterior mounted). The feeders are in flex with only L1, L2 and N.

Sounds like they used the flex as the EGC which is not permitted.

 

[Strathead]

Sounds like they used the flex as the EGC which is not permitted.

250.118 is the code reference for this. Not allowed over 20 amps, but that isn't what this sounds like.

Is there an exception in the NEC 2023 that allows us to retain the existing interior subpanel with only L1, L2, and N conductors, but no ground, on a residential property without requiring an upgrade to the subpanel to include a ground connection when installing a solar system?
The Main panel on the exterior is built per NEC 2023. The subpanel will be fed via the feeders from the main panel. The subpanel will be on the same structure as the main panel.

It sounds like an old house that had a main panel inside that was originally the Service disconnect and someone upgraded at a future date without properly splitting the neutrals and grounds. The answer to your question is no, there isn't an exception. If you want a better discussion though, provide more details. Is there only one bus in the interior panel for both neutrals and grounds? Where is the grounding electrode system bonded to the neutral? Is there a main breaker in the interior panel? What does the exterior "main" panel feed?

FYI, my house was not done right the first time. I had a similar issue. But one AHJ item in the code that can change over the years is "nearest the point of entry." In my county it is immediately. In the next county over it is 10'. In my house before I redid it, it was 25' through the attic.

 

[infinity]

The subpanel is back to back with the main service panel. The subpanel which is located inside the house is being fed via the feedthrough lugs from the Main panel (exterior mounted). The feeders are in flex with only L1, L2 and N.

Bottom line is the feeder requires an EGC. There currently is no exception that would allow the feeder to not have an EGC run with the circuit conductors unless at the time of installation the flex was permitted to be used as the EGC.

 

[msi99]

You're correct. This is an old house, with the subpanel being a split bus configuration ( stab lock), and it looks like an upgrade was performed on a later date by adding a new feedthrough main panel on the exterior without rectifying the ground issue. The new main panel does not have other loads. When the upgrade was performed the flex may have been approved to use as EGC. If we were to add solar to this system, would it be justified to address all the existing code issues, including the EGC in the subpanel? This would essentially require rewiring the entire house to bring the electrical system up to the latest code standards.

250.118 is the code reference for this. Not allowed over 20 amps, but that isn't what this sounds like.

It sounds like an old house that had a main panel inside that was originally the Service disconnect and someone upgraded at a future date without properly splitting the neutrals and grounds. The answer to your question is no, there isn't an exception. If you want a better discussion though, provide more details. Is there only one bus in the interior panel for both neutrals and grounds? Where is the grounding electrode system bonded to the neutral? Is there a main breaker in the interior panel? What does the exterior "main" panel feed?

FYI, my house was not done right the first time. I had a similar issue. But one AHJ item in the code that can change over the years is "nearest the point of entry." In my county it is immediately. In the next county over it is 10'. In my house before I redid it, it was 25' through the attic.

 

[Buck Parrish]

With few eceptions , It's ussually pretty easy to isolate the neutral from the equipment ground. Just run a new wire and install a grounding bar. Remove the bonding jumper off the sub panels neutral bar.

It doesn't have anything to do with rewiring the house.

 

[infinity]

You're correct. This is an old house, with the subpanel being a split bus configuration ( stab lock), and it looks like an upgrade was performed on a later date by adding a new feedthrough main panel on the exterior without rectifying the ground issue. The new main panel does not have other loads. When the upgrade was performed the flex may have been approved to use as EGC

Metal raceways were at one time permitted for use as the EGC so you will see it done that way in older installations. I'm assuming that the neutral in this old panel is not bonded and it's wired just like a standard feeder with the metal raceway being the EGC. Normally that would be grandfathered in. Regarding the new solar someone else may know the answer.

 

[Buck Parrish]

Is that an old FP panel? If so chunking it and installing a new sub panel might be a good idea. If you get a new ML panel. it will have the grounding and neutral isolated,

 

[jaggedben]

First, try to ascertain if you've got flexible metallic conduit or MC cable. The latter might act as a compliant EGC. See 250.118(10).

I think you shouldn't install a solar breaker in the subpanel if the subpanel doesn't have a good, code compliant EGC. (Also it's an FPE.) But so far I've not been asked to tear apart walls to fix that sort of thing when it was previously existing and I connected solar upstream. (And I've seen worse, like a cloth covered cable to a sub, no EGC and no metal flex at all. ) Stick the solar in the main panel or insert a subpanel outside.

In a couple cases out of the goodness of my heart I ran a separate 6awg EGC to a sub, following 250.120(C) and 250.130(C), even though that's supposed to only be for receptacles. Inspectors were oblivious, and figured I made it safer without costing the homeowner an arm and a leg.

 

[jaggedben]

Is that an old FP panel? If so chunking it and installing a new sub panel might be a good idea. If you get a new ML panel. it will have the grounding and neutral isolated,

While I completely agree with replacing old FPEs, that's a completely different scope and cost than fixing a feeder that doesn't have an EGC.

 

[jaggedben]

Is there an exception in the NEC 2023 that allows us to retain the existing interior subpanel with only L1, L2, and N conductors, but no ground, on a residential property without requiring an upgrade to the subpanel to include a ground connection when installing a solar system?
...

There's no exception. But if you keep the existing sub and feeder unrelated to your solar scope of work, in my experience AHJs will grandfather it.

(To restate what I said earlier.)

 

[david]

Just thinking about the possibilities

What if the service was repaired under the 2020 code. Not sure what the 2023 did with the emergency disconnect

There are alot of service repaired that do not involve changing out an existing panel

 

[wwhitney]

You're correct. This is an old house, with the subpanel being a split bus configuration ( stab lock), and it looks like an upgrade was performed on a later date by adding a new feedthrough main panel on the exterior without rectifying the ground issue. The new main panel does not have other loads.

As the exterior panel has no loads and just feeds-thru to the interior panel, as long as the interior panel meets all the requirements for the service disconnect, the exterior panel can be labeled "Emergency Disconnect--Not Service Equipment" under 230.85(3).

Cheers, Wayne

 

[Eddie702]

I would put a ground in the flex if the flex has room, install a ground bar and separate the grounds and neutrals and tell the HO they should replace the panel.

What does it have for GEC and where do they terminate?

 

[david]

subpanel with only L1, L2, and N conductors, but no ground, on a residential property without requiring an upgrade to the subpanel to include a ground connection when installing a solar system?

Ok let's say the disconnect outside is an emergency disconnect, and the panel inside is supplied with 3 wire supply conductors.

The panel inside would not be a subpanel it would be the service (panel)

So your question becomes can you add solor without changing the supply to four wire and without separating the neutral and equipment grounds

Or are you asking if a emergency disconnect outside is allowed as the panel to make a line side tap for the solar

I'm not sure what your asking

 

[david]

I don't see anything in 230.85 (3) in conflict with 230 .82 (6)