GEC for PV Disconnects

[ohmti787]

For a supply side connection, do I really need a GEC? Some AHJ's require it, some don't care and some won't accept it because they're saying it creates a parallel pathway for a ground fault (which kinda makes sense to me). Honestly, I don't think it's needed as long as the N-G are bonded in the disconnect, but can I get some insight on this please? Thanks

 

[petersonra]

For a supply side connection, do I really need a GEC? Some AHJ's require it, some don't care and some won't accept it because they're saying it creates a parallel pathway for a ground fault (which kinda makes sense to me). Honestly, I don't think it's needed as long as the N-G are bonded in the disconnect, but can I get some insight on this please? Thanks

I think you need it if the code says it is required.

 

[pv_n00b]

For a supply side connection, do I really need a GEC? Some AHJ's require it, some don't care and some won't accept it because they're saying it creates a parallel pathway for a ground fault (which kinda makes sense to me). Honestly, I don't think it's needed as long as the N-G are bonded in the disconnect, but can I get some insight on this please? Thanks

This is a burning question in pre-2020 NEC days since it was up to interpretation if you put the N-G bond in the PV disconnect or not. So it depends on the code cycle you are on and the AHJ. The 2020 NEC is specific, N-G bond and GEC in the PV disconnect. In general, you have to have a GEC anywhere there is a N-G bond.

 

[wwhitney]

In general, you have to have a GEC anywhere there is a N-G bond.

Or conductively upstream. E.g. in the case of the OP, if the GEC is already routed to somewhere upstream of the normal/PV service split (e.g. the meter), then there's no need for any GEC in the PV service disconnect.

Cheers, Wayne

 

[ohmti787]

This is a burning question in pre-2020 NEC days since it was up to interpretation if you put the N-G bond in the PV disconnect or not. So it depends on the code cycle you are on and the AHJ. The 2020 NEC is specific, N-G bond and GEC in the PV disconnect. In general, you have to have a GEC anywhere there is a N-G bond.

But wouldn't that create a parallel gnd fault pathway as well?
This has been such a gray area. If we bond the G-N at the PV disconnect (for either a load or a supply side connection), what's the difference between landing the EGC at the ground bar in the MSP vs tapping the existing GEC with a bare ground. The existing GEC is still connected to the ground bar in the MSP, just like the EGC would be.

 

[wwhitney]

But wouldn't that create a parallel gnd fault pathway as well?

Yes, with multiple service disconnects you are probably going to have parallel paths. Either directly through the GES via the separate GEC connections in each disconnect. Or, if you are able to land the GEC upstream of the split in the service conductors, then if the separate EGC systems ever end up bonded to the same item.

This has been such a gray area. If we bond the G-N at the PV disconnect (for either a load or a supply side connection)

You wouldn't bond G-N at a PV disconnect for a load side connection. There would just be the one N-G bond at the upstream existing service panel.

Cheers, Wayne

 

[jaggedben]

Parallel ground fault paths isn't the concern. The concern is parallel paths for grounded conductor (neutral) current. But the code has made clear for decades that parallel neutral current on the GEC and GES happens sometimes and is acceptable, especially when there are multiple service disconnects. That's why there are requirements that apply to GECs and nothing else, such as bonding on both ends. And a supply side PV disconnect is no different than an additional service disconnect in this respect, no matter the name put on it.

All this is notwithstanding that some AHJs may not understand it.

 

[pv_n00b]

But wouldn't that create a parallel gnd fault pathway as well?

Yes, but parallel ground fault current paths are perfectly acceptable. The more low impedance paths there are for ground fault current the better.

 

[ohmti787]

So I guess another way around these supply side connections is to remove the N-G bond at the disconnect and just run the EGC all the way down to the Gnd bar at the MSP? That way I can get rid of the N-G bonding jumper AND the GEC at the disconnect.

 

[pv_n00b]

So I guess another way around these supply side connections is to remove the N-G bond at the disconnect and just run the EGC all the way down to the Gnd bar at the MSP? That way I can get rid of the N-G bonding jumper AND the GEC at the disconnect.

For supply side interconnections you can't run an EGC, since there is no upstream OCPD to base the size on. Some people run a supply side bonding jumper but since this is not a separately derived system the SSBJ is not called for. The NEC through the 2017 version really lets us down here. There needs to be a path for the ground fault current on the PV equipment to get back to the neutral conductor in the service. You are probably going to have metal conduct from the PV disconnect to the service entrance that can act as the path for the ground fault current. Otherwise, you can run a conductor sized as an SSBJ from the PV disconnect ground bar to the service equipment ground bar.

 

[ggunn]

We have been talking about this in here literally for years. Many jurisdictions in Texas in the past required an ECG though the PV disco back to the service based on the OCPD rating of the PV disconnect for line side interconnections with no neutral to ground bond in the disco. Others required the neutral to ground bond in the disco and a GEC from the disco back to the service ground instead of an EGC. It was a pain keeping track of what each AHJ wanted.

Lately, however, we have been doing them all the latter way, at least for commercial PV, and so far none have been bounced for it.

 

[pv_n00b]

We have been talking about this in here literally for years. Many jurisdictions in Texas in the past required an ECG though the PV disco back to the service based on the OCPD rating of the PV disconnect for line side interconnections with no neutral to ground bond in the disco. Others required the neutral to ground bond in the disco and a GEC from the disco back to the service ground instead of an EGC. It was a pain keeping track of what each AHJ wanted.

Lately, however, we have been doing them all the latter way, at least for commercial PV, and so far none have been bounced for it.

The variation with AHJs is a real problem. We usually put the bond in the PV disconnect and had an AHJ approve a design and issue a permit but they put a comment in the plan review plan set that the bond can't be in the disconnect. The EPC never noticed the comment and did not pass it on to us, the system was installed and failed inspection. Now they will need another utility shutdown to remove the bond in the disconnect.

 

[ggunn]

The variation with AHJs is a real problem. We usually put the bond in the PV disconnect and had an AHJ approve a design and issue a permit but they put a comment in the plan review plan set that the bond can't be in the disconnect. The EPC never noticed the comment and did not pass it on to us, the system was installed and failed inspection. Now they will need another utility shutdown to remove the bond in the disconnect.

Yeah, that's a problem; I feel your pain. The larger issue for us is that we operate in a hundred or so AHJ territories, and keeping track of what we can and have to do where is a daunting task.

 

[pv_n00b]

Thousands of AHJs. It gets crazy for someone working across many states. It's even worse when the interpretation at a given AHJ can change depending on the plan checker you get or the inspector who comes out. A lot of AHJs can't seem to clearly articulate what their requirements are, they say to submit for a permit and they'll decide if they like it or not that day.

 

[ggunn]

Thousands of AHJs. It gets crazy for someone working across many states. It's even worse when the interpretation at a given AHJ can change depending on the plan checker you get or the inspector who comes out. A lot of AHJs can't seem to clearly articulate what their requirements are, they say to submit for a permit and they'll decide if they like it or not that day.

You: The preacher
Me: The choir

I would add a smileyface but it ain't all that funny.

 

[don_resqcapt19]

The solar industry has always tried to get away with not treating a supply side connection as service equipment, but since it is connected directly to the utility supply the same hazards exist with this disconnect as will any other service disconnect. These should have always been installed exactly like any other service disconnect, but as others have said the code was not really clear.

The 2020 made a great start at fixing this issue and the 2023 goes beyond and actually calls a supply side PV disconnect a service disconnect.

There was a somewhat heated fight over this between CMP 4 and CMP 10, with CMP 10 actually creating a new article in the first draft report that would have conflicted with the rules in 705. The Correlating Committee stepped in and created a task group with members from panels 4, 5, and 10 to work this out.

 

[ggunn]

The solar industry has always tried to get away with not treating a supply side connection as service equipment...

Speaking for myself and my employer, we were not trying to "get away" with anything when we did otherwise. We just did whatever the AHJs required of us in order not to fail an inspection; many of them directed us to leave ground and neutral unbonded in the PV AC disconnect of a supply side interconnected PV system and run an EGC all the way back to the service from the inverter(s). Many of those AHJs are now changing their rules and we will comply with them. Personally, I don't and never did care which way I needed to design systems; I only am concerned with passing inspection and moving on.

 

[jaggedben]

Speaking for myself and my employer, we were not trying to "get away" with anything when we did otherwise. We just did whatever the AHJs required of us in order not to fail an inspection; many of them directed us to leave ground and neutral unbonded in the PV AC disconnect of a supply side interconnected PV system and run an EGC all the way back to the service from the inverter(s). Many of those AHJs are now changing their rules and we will comply with them. Personally, I don't and never did care which way I needed to design systems; I only am concerned with passing inspection and moving on.

...and I bet you wouldn't mind if they were all consistent.

@don_resqcapt19
FWIW (not much, I know) I have put forward that Art 230 should be applied to supply-side PV disconnects since I joined this forum over 11 years ago. I have never really understood why CMP 4 made an issue of this when the mention of 230.40 Ex. 5 in 230.71(B) seemed to give the industry the leeway it needed.

 

[PWDickerson]

I am curious Don about your comment that the PV industry has been trying to get away with not treating a supply-side connection as an additional service. Is there really a significant contingent in the industry that pushed for that? Seems like more folks in the industry were pushing the other way. Wiring them like service equipment always seemed like a no-brainer to me.

 

[ggunn]

I am curious Don about your comment that the PV industry has been trying to get away with not treating a supply-side connection as an additional service. Is there really a significant contingent in the industry that pushed for that? Seems like more folks in the industry were pushing the other way. Wiring them like service equipment always seemed like a no-brainer to me.

IMO it was just an ill informed bad choice of words. There isn't any significant advantage - cost or otherwise - of not treating line side interconnections as services, so there is nothing to get away with.