GEC in Parallel Raceways

[pvgreeze]

Hi everyone, I've been looking through threads for a discussion on this topic, and I cannot find anything specific to the issue I'm facing. The AHJ in question uses the 2017 NEC, so all references will be to that, though I think the language of the code is consistent in later versions...

I have a PV Disconnect outside of a building, line side interconnection, that is a separate service disconnect [230.2(A)(5)]. In this disconnect, I am bonding the ground (grounding) and the neutral (grounded) with a main bonding jumper sized off Table 250.102(C)(1) [250.24(B) & 250.28]. Now, I need to connect the ground in PV Disconnect to the building grounding electrode system [250.58 and 690.47(A)]. This connection will be achieved with a grounding electrode conductor (GEC), which is sized off of Table 250.66 for this building, which now has multiple [service] disconnecting means in separate enclosures [250.64(D)(2)].

My grounding electrode conductor is sized off of NEC 250.66. For this PV system, the OCPD is a 1000A fuse, with three parallel sets of service entrance conductors off the line side of the existing main circuit breaker, in parallel ferrous raceways.

Here is where I am confused. Table 250.66 requires me to only have a single 3/0 Cu GEC. A conventional service would have this GEC connected between the grounding busbar in the main switchboard and the building grounding electrode system (GES) - building steel, pipes, ground rods, etc. However, my PV Disconnect is outside of the building, and I need to tie this PV Disconnect GES to the building GES, as outlined above, with a single 3/0 Cu GEC. The easiest method to do this would be to run this GEC with the parallel ungrounded conductors & neutrals to the existing main circuit breaker and connect within the existing switchboard.

My questions are:

1. Can I run a single GEC in the same raceway as phase and neutral (grounded) conductors to the point of inteconnection/the most practical tie in point to connect to the existing GES
2. Can I run a single GEC in one raceway when there are multiple parallel raceways, several of which would not contain GECs

Would love to know thoughts and comments. I've read through several related threads, and didn't see anything that addressed this specific concern. I'll link below for reference:

GEC for PV Disconnects

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...

forums.mikeholt.com

Running grounding electrode conductor in same conduit as phase conductors

When running an grounding electrode conductor in order to bond (2) grounding electrodes (DC and AC electrode) can the grounding electrode conductor be run with the phase conductors and equipment ground conductor running between two pieces of equipment. For instance in a PV system if there is...

forums.mikeholt.com

 

[ggunn]

You need a full sized EGC as determined by the rating of the OCPD in every conduit when you have parallel sets in separate conduits. I don't see why a GEC would be different, but are you sure it's a GEC you need and not an EGC?

 

[jaggedben]

Hi everyone, I've been looking through threads for a discussion on this topic, and I cannot find anything specific to the issue I'm facing. The AHJ in question uses the 2017 NEC, so all references will be to that, though I think the language of the code is consistent in later versions...

Actually, for what it's worth, the 2020 NEC changed things a lot with the introduction of 250.25. In the 2017, it is still unclear if you are required to treat grounding and bonding of a supply side PV disconnect the same as an additional service disconnect.

I have a PV Disconnect outside of a building, line side interconnection, that is a separate service disconnect [230.2(A)(5)]. In this disconnect, I am bonding the ground (grounding) and the neutral (grounded) with a main bonding jumper sized off Table 250.102(C)(1) [250.24(B) & 250.28].

See above. Under the 2017 one could arguably just run a supply-side bonding jumper to the PV disconnect, and not install a main bonding jumper in the disconnect. I've always thought that made no sense and that such a disconnect should be treated as a service disconnect, but under the 2017 one can make the argument either way. And in your situation it could get you out of doing the thing you don't want to do, i.e. install a new separate GEC along a new route.

...

My questions are:

1. Can I run a single GEC in the same raceway as phase and neutral (grounded) conductors to the point of inteconnection/the most practical tie in point to connect to the existing GES

The only objection I know of would be if the AHJ thinks it might cause objectionable current, which is not defined. Otherwise, as long as you bond both ends of the raceway per 250.64(E) (assuming a metal raceway), then I don't see a violation.

1. Can I run a single GEC in one raceway when there are multiple parallel raceways, several of which would not contain GEC.

I don't see any problem with this.

@ggunn will probably be along soon to say that it all depends on whether the particular AHJ agrees with your reasoning or has any particular rules about how it should be done. And in this case, especially when still on the 2017 NEC, I would very much agree.

 

[ggunn]

@ggunn will probably be along soon to say that it all depends on whether the particular AHJ agrees with your reasoning or has any particular rules about how it should be done. And in this case, especially when still on the 2017 NEC, I would very much agree.

No need, since you already did.

 

[jaggedben]

You need a full sized EGC as determined by the rating of the OCPD in every conduit when you have parallel sets in separate conduits. I don't see why a GEC would be different, but are you sure it's a GEC you need and not an EGC?

He sure seems to be describing a GEC, and table 250.66 maxes out at 3/0 copper.

 

[ggunn]

He sure seems to be describing a GEC, and table 250.66 maxes out at 3/0 copper.

I don't run a GEC in conduit with the CCCs, but if I did I think I would do the same as if it were the EGC, i.e. full size in every conduit.

 

[pvgreeze]

You need a full sized EGC as determined by the rating of the OCPD in every conduit when you have parallel sets in separate conduits. I don't see why a GEC would be different, but are you sure it's a GEC you need and not an EGC?

He sure seems to be describing a GEC, and table 250.66 maxes out at 3/0 copper.

Yes to jaggedben.

See above. Under the 2017 one could arguably just run a supply-side bonding jumper to the PV disconnect, and not install a main bonding jumper in the disconnect. I've always thought that made no sense and that such a disconnect should be treated as a service disconnect, but under the 2017 one can make the argument either way. And in your situation it could get you out of doing the thing you don't want to do, i.e. install a new separate GEC along a new route.

That makes sense, and obviously there are very easy to follow rules in article 250.102(C)(2). Theoretically speaking, one could argue that both an SSBJ following 250.102(C)(2) or a MBJ and GEC (as outlined in my initial post) would achieve the same ends; tieing the PV system to the building GES. I think another strange gray area is, per 250.64(D)(2)(2), I can connect my GEC to an EGC "installed with the feeder," which one could read as stating that the circuit on the load side of the PV Disconnect (feeder) can be connected to the grounding electrode system at a point downstream of the PV Disconnect using the MBJ and GEC approach.