250.24(C) Grounded Conductor Brought to Service Equipment

[ggunn]

Here's a situation I have seen many times: Immediately behind the meter there is a gutter and several fused discos are connected to Polaris blocks inside it. Neutral is bonded to the GEC in the gutter and not in any of the discos. A PV system is installed on the supply side via open ports in the Polaris blocks. Would you bond neutral to ground in the PV AC disco?

 

[jaggedben]

Is the new connection supplying a new load? (I have no direct experience with solar.)

No, solar is not a load. (In many cases there might be a very small incidental load associated with monitoring.)

Do the service conductors branch off as if one was adding another service disconnect?

Yes.

Does it effectively become another service panel, and be drawn as such in a one-line?

It would be drawn the same on a one line, yes.

If yes, then I might be inclined to agree that it should be wired as such, with bonding.

For a system with the connection made after the main, like a sub-panel, then no bond.


Please tell me whether I am at least grasping the gist of the conversation.

I think you are grasping it.

 

[jaggedben]

While solar is indeed arguably not a load it is considered a load in the NEC.

Not sure why you'd say that.

The inverter needs to draw AC power before it will invert the DC and it always needs control power even at night.

I think this depends on inverter design and isn't true in all cases.

 

[pv_n00b]

I disagree that the NEC is clear and concise on this issue, but at the end of the day it really doesn't matter what you and I think. The AHJ has the final say and it doesn't matter, either, whether they are right or wrong. If designing systems the way they direct me to were to result in an unsafe or malfunctioning condition, then I might go to the mat over it, but it doesn't.

I have to disagree. If it were just up to the AHJ to make up all the rules as they went along nothing could get done. The job of the AHJ is to make sure the codes and standards legally adopted by the state and locality are applied to projects in their jurisdiction. When an AHJ comes along who wants to make up their own rules and ignore the law they need to be reined in. But then again, it is Texas.

 

[pv_n00b]

Grounding of the supply side PV disconnect is now clearly defined in the 2020 NEC in the new section 250.25. It's done, stick a fork in it and move on. All this discussion about grounding depending on if a supply side PV disconnect is a service disconnect is old news. Let's argue about something more interesting.

 

[electrofelon]

Let's argue about something more interesting.

Fine, I'm going back to the daylight saving time thread.....

 

[ggunn]

I have to disagree. If it were just up to the AHJ to make up all the rules as they went along nothing could get done. The job of the AHJ is to make sure the codes and standards legally adopted by the state and locality are applied to projects in their jurisdiction. When an AHJ comes along who wants to make up their own rules and ignore the law they need to be reined in. But then again, it is Texas.

Reigned in by whom, exactly? It certainly isn't my job to take an AHJ to the mat over something like this. If it resulted in an unsafe or malfunctioning system, I would feel differently, but in this case it doesn't. I don't really care if I have to bond N to G in the disco or not. I very much care if something I design will fail final inspection, though, so I will build it the way they want it.

 

[ggunn]

Here's a situation I have seen many times: Immediately behind the meter there is a gutter and several fused discos are connected to Polaris blocks inside it. Neutral is bonded to the GEC in the gutter and not in any of the discos. A PV system is installed on the supply side via open ports in the Polaris blocks. Would you bond neutral to ground in the PV AC disco?

No takers?

 

[ggunn]

Grounding of the supply side PV disconnect is now clearly defined in the 2020 NEC in the new section 250.25. It's done, stick a fork in it and move on.

Clearly? Shirley, you must be joking.

 

[jaggedben]

I disagree that the NEC is clear and concise on this issue, but at the end of the day it really doesn't matter what you and I think. The AHJ has the final say and it doesn't matter, either, whether they are right or wrong. If designing systems the way they direct me to were to result in an unsafe or malfunctioning condition, then I might go to the mat over it, but it doesn't.

I gotta say, I kinda don't see any point is of posting this kind of thing a forum like this. To the extent you're correct then we might as well all just log off. Or at least that would apply to at least half the content on this forum, which deals directly with questions of code interpretation. In this vein...

Reigned in by whom, exactly? It certainly isn't my job to take an AHJ to the mat over something like this. ...

I push back on ill-informed AHJ requirements or requests as a regular matter of course, and about half the time I'd say I'm successful. It's certainly worth it to create the precedent when it's an AHJs the company works with all the time. And the more you can get code-consistent enforcement across different AHJs, the less you have to worry about communicating esoteric AHJ requirements to your field installers.
Rarely have I truly had to 'go to the mat' but in the one case that comes to mind I eventually won, and it meant the difference between that installation getting approved and interconnected vs. uninstalled with a big loss for everybody. And I won because the code I cited was in my favor. Maybe it wouldn't have worked in Texas, I don't know. But we don't all live there.

 

[jaggedben]

No takers?

Here's a situation I have seen many times: Immediately behind the meter there is a gutter and several fused discos are connected to Polaris blocks inside it. Neutral is bonded to the GEC in the gutter and not in any of the discos. A PV system is installed on the supply side via open ports in the Polaris blocks. Would you bond neutral to ground in the PV AC disco?

The GEC termination location is an uninteresting part of the question, in my opinion. That is one of the options allowed in 250.64(D), specifically it's 250.64(D)(3).

Should I presume all the existing service disconnects have MBJs as required by 250.24(B)? If not, I might fix that, as it's potentially dangerous without them and if anything goes wrong after my company is the last to touch the service...

As far as the PV disco, I would bring the neutral to the new PV disco and put an MBJ there. And if the AHJ objected and I wasn't on the 2020 NEC yet, I'd probably be like, "okay, whatever, how do you want me to bond this disconnect?". And if I was on the 2020 NEC already, I would begin by saying "Have you read this new section 250.25?".

 

[BradPV]

I never said there can't be multiple pieces of service equipment, and multiple disconnects. But 99.8% of the time these together will still be one service. We can discuss whether the PV disconnect is wired "like" a service, i.e. neutral bonded, but that doesn't make it another service.

We will just have to agree to disagree I guess. The way I read the definitions of service and service equipment the supply side tap creates a "new" one, not "like" one.

 

[BradPV]

I push back on ill-informed AHJ requirements or requests as a regular matter of course, and about half the time I'd say I'm successful. It's certainly worth it to create the precedent when it's an AHJs the company works with all the time. And the more you can get code-consistent enforcement across different AHJs, the less you have to worry about communicating esoteric AHJ requirements to your field installers.
Rarely have I truly had to 'go to the mat' but in the one case that comes to mind I eventually won, and it meant the difference between that installation getting approved and interconnected vs. uninstalled with a big loss for everybody. And I won because the code I cited was in my favor. Maybe it wouldn't have worked in Texas, I don't know. But we don't all live there.

I agree with you on this one. I have pushed back on a couple of AHJ's here on this subject in particular even to the point of bringing their supervisors into the argument. I am trying to keep consistency for the designers and install teams so that they don't have to wire/draw depending on who's jurisdiction they are in. The one good thing about this in NC is that we have the state sanctioned drawings to point back to, though that didn't even work until the supervising inspector got involved.

 

[BradPV]

Not sure why you'd say that.

You said yourself: "No, solar is not a load. (In many cases there might be a very small incidental load associated with monitoring.)" A load is a load.

I think this depends on inverter design and isn't true in all cases.

This is a true statement, I was speaking to the systems currently being used by the company I am associated with.

Here's a situation I have seen many times: Immediately behind the meter there is a gutter and several fused discos are connected to Polaris blocks inside it. Neutral is bonded to the GEC in the gutter and not in any of the discos. A PV system is installed on the supply side via open ports in the Polaris blocks. Would you bond neutral to ground in the PV AC disco?

250.24 and 250.25 actually allow bonding of the neutral ahead of the disconnect so the trough could be the bonding point. BUT again I am going for consistency for the install teams who I do not expect to go thoroughly through the code book and to be involved in forums like this because unfortunately most are not inclined to keep their wits sharpened by seeking knowledge and are as likely to wire by rote as they are by drawings.

 

[ggunn]

I push back on ill-informed AHJ requirements or requests as a regular matter of course, and about half the time I'd say I'm successful. It's certainly worth it to create the precedent when it's an AHJs the company works with all the time. And the more you can get code-consistent enforcement across different AHJs, the less you have to worry about communicating esoteric AHJ requirements to your field installers.
Rarely have I truly had to 'go to the mat' but in the one case that comes to mind I eventually won, and it meant the difference between that installation getting approved and interconnected vs. uninstalled with a big loss for everybody. And I won because the code I cited was in my favor. Maybe it wouldn't have worked in Texas, I don't know. But we don't all live there.

As a matter of fact I have indeed pushed back on AHJs a few times (and won a few times) when it was an important issue, but this one isn't. I choose my battles.

 

[electrofelon]

We will just have to agree to disagree I guess. The way I read the definitions of service and service equipment the supply side tap creates a "new" one, not "like" one.

See 230.2. I don't see any allowance there for a second service for this application. Also see 230.40 EX #5.

 

[ggunn]

I am trying to keep consistency for the designers and install teams so that they don't have to wire/draw depending on who's jurisdiction they are in.

Good luck with that one. We maintain a document of many pages which lines out the special requirements of all the AHJs' territories we operate in. The N-G bonding in the disco yes or no is just one of many differences we encounter. It's a pain.

 

[kwired]

I never said there can't be multiple pieces of service equipment, and multiple disconnects. But 99.8% of the time these together will still be one service. We can discuss whether the PV disconnect is wired "like" a service, i.e. neutral bonded, but that doesn't make it another service.

If they connect to same utility source then it is still one service. You are allowed six disconnecting means per service, with some exceptions, and a PV system potentially can be one those exceptions.

 

[wwhitney]

See 230.2. I don't see any allowance there for a second service for this application.

What about 230.2(A)(5) "Parallel power production systems"?

Cheers, Wayne

 

[kwired]

Here's a situation I have seen many times: Immediately behind the meter there is a gutter and several fused discos are connected to Polaris blocks inside it. Neutral is bonded to the GEC in the gutter and not in any of the discos. A PV system is installed on the supply side via open ports in the Polaris blocks. Would you bond neutral to ground in the PV AC disco?

Because that is what you do with all items enclosing service conductors? The supply side of the disconnect is still service conductors.

You are required to bring the grounded service conductor to all service disconnecting means and bond it there whether there is any load utilizing the grounded conductor or not. Load side is feeder or branch circuit conductors, an EGC is required but the grounded conductor is not if the load doesn't require one. PV isn't a load and that can make it more confusing, but the utility has the established ground reference if it is a grounded system.