connecting EGC and neutral for a line side tap (supply side connection)

[iwire]

FWIW, this looks like a "the grass is green vs. the sky is blue" argument to me.

I agree, it just opinion and view point.

If the PV is interconnected on the supply side, the PV AC disco disconnects the PV system from the utility. It does not disconnect the building from the utility; there is another switch that does that. If the PV system is interconnected on the load side, then there is one switch that does both.

I agree again.

 

[jaggedben]

Except it is not serving a load, it is serving a source unless you are designing systems with no output. That to me is both intresting and significant.

How is it interesting with respect to anything in articles 230 or 250? How is it interesting with respect to any safety aspect regarding grounding, bonding, grouping, or number?

To each their own, the CMPs will end up clearfying things eitherway eventually.

You seem to have a lot of confidence in this happening on its own. I don't. :lol:

FWIW, this looks like a "the grass is green vs. the sky is blue" argument to me. If the PV is interconnected on the supply side, the PV AC disco disconnects the PV system from the utility. It does not disconnect the building from the utility; there is another switch that does that. If the PV system is interconnected on the load side, then there is one switch that does both.

If the PV system is on the building, then it's just more equipment on the building. A supply side disconnect for it is no different from, say, an air conditioner on the roof with its own service disconnect.]

I agree, it just opinion and view point.

Physics is just an opinion and viewpoint? Perhaps you just haven't been following the thread closely enough.

 

[iwire]

How is it interesting with respect to anything in articles 230 or 250? How is it interesting with respect to any safety aspect regarding grounding, bonding, grouping, or number?

It is interesting to me from the safety aspect of believing you are killing the building power vs the supply side PV system.

I am fine if you find that uninteresting.

You seem to have a lot of confidence in this happening on its own. I don't. :lol:

A man can dream.

A supply side disconnect for it is no different from, say, an air conditioner on the roof with its own service disconnect.

If you ignore the fact one is a load and one is a source.

 

[ggunn]

If the PV system is on the building, then it's just more equipment on the building. A supply side disconnect for it is no different from, say, an air conditioner on the roof with its own service disconnect.

Well, duh. I have never seen an HVAC unit with its own service disco, but I guess it could happen.

In both cases opening the disco obviously only separates the equipment in question, not the entire building, from the utility.

 

[electrofelon]

I admit that I am a bit baffled by the opinion that a PV disconnect is different than a service disconnect in terms of safety and purpose. Maybe I am off base, but I think of the primary purpose of a service disconnect is to remove power from the building in case of an emergency such as fire. During an emergency fireman may be spraying water and cutting through walls, etc. I don't see them not caring if the PV disconnect is off because it "doesn't supply a load" to the building. I think the electrons will break the rules and supply the load of an ax through a feeder to a combiner panel.

 

[jaggedben]

I admit that I am a bit baffled by the opinion that a PV disconnect is different than a service disconnect in terms of safety and purpose. Maybe I am off base, but I think of the primary purpose of a service disconnect is to remove power from the building in case of an emergency such as fire. During an emergency fireman may be spraying water and cutting through walls, etc. I don't see them not caring if the PV disconnect is off because it "doesn't supply a load" to the building. I think the electrons will break the rules and supply the load of an ax through a feeder to a combiner panel.

Exactly. Thank you.

Also, if some AHJ decides that it's okay to have 12 handles (6 for PV, 6 for loads) instead of 6 to remove power from all said utility-connected circuits that a firefighter might possibly put an ax through, the firefighters might not be inclined to agree with that interpretation.

To repeat, I'm somewhat agnostic on whether the code should be changed. But from the point of view of anything besides labeling, I really don't get why the PV disconnect should be treated differently with regards to any safety consideration.

 

[texie]

In all the debate in this thread and the numerous previous post on this subject my question is this: if you don't bond the neutral what is the fault return path in the event there is a short to the enclosure from a POCO side conductor?

 

[iwire]

I admit that I am a bit baffled by the opinion that a PV disconnect is different than a service disconnect in terms of safety and purpose. Maybe I am off base,

I do not think anyone here is off base, we simply have different opinions about something that has not been made clear in the code.

The fact so many have differing opinions on it strongly suggests to me that the CMP will have to address this to clarify things.

 

[electrofelon]

In all the debate in this thread and the numerous previous post on this subject my question is this: if you don't bond the neutral what is the fault return path in the event there is a short to the enclosure from a POCO side conductor?

There is still a bonding jumper back to the neutral in the service equipment.

 

[texie]

There is still a bonding jumper back to the neutral in the service equipment.

How does that make a fault return path if the disconnect for the line side connection is in a different enclosure? Are you saying that the enclosure for the disconnect is bonded per 250.92? But wait! That would mean it is a "service" disconnect.

 

[ggunn]

How does that make a fault return path if the disconnect for the line side connection is in a different enclosure? Are you saying that the enclosure for the disconnect is bonded per 250.92? But wait! That would mean it is a "service" disconnect.

It is bonded to the EGC, the same as every other metal enclosure containing the CCC's, not the neutral.

 

[texie]

It is bonded to the EGC, the same as every other metal enclosure containing the CCC's, not the neutral.

And that EGC is connected to what at the other end?

 

[jaggedben]

And that EGC is connected to what at the other end?

Ultimately, to the main bonding jumper at a service enclosure, and the service grounded conductor.

The way I look at it, you have to comply with 250.4(B)(4) no matter what names you call the objects you install. At least that section of the code appeals rather directly to physics.

 

[texie]

Ultimately, to the main bonding jumper at a service enclosure, and the service grounded conductor.

The way I look at it, you have to comply with 250.4(B)(4) no matter what names you call the objects you install. At least that section of the code appeals rather directly to physics.

Still not understanding the fault return path. In some system setups/types there would be no path at all, let alone a compliant and low impedance path. In many cases this could lead to catastrophic burn down if you had a service conductor fault in the PV line side disconnect.
I will be the first to admit that the code needs some work in this area but I think the intent is there to always require bonding of the grounded conductor at the disconnect. Look, I think many of you are a smart and well informed bunch and I'm surprised that some do not see the potential serious hazard here.

 

[wwhitney]

Still not understanding the fault return path.

I assume the PV line-side disconnect without neutral-ground bond would grab an EGC either from the other service, or from the GES. Either way it is connected to the neutral-ground bond in the other service.

Cheers, Wayne

 

[c_picard]

I assume the PV line-side disconnect without neutral-ground bond would grab an EGC either from the other service, or from the GES. Either way it is connected to the neutral-ground bond in the other service.

Cheers, Wayne

An EGC is now being asked to carry fault current from the POCO, via a meandering path through other equipment, back to the source?

If I have for example a 60A OCPD in the disconnect used for the PV supply side connection, we're talking about a 10AWG Cu conductor? Granted it would only be an 8AWG if we use a main bonding jumper, but still. I'd rather see that line-side fault to the enclosure take the shortest path possible back to the grounded conductor, and I think existing Code language supports that view.

Then again, if it really doesn't make a difference, I'm all for striking a few tables and hundreds of lines of text