705.12 (D) re- visited

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Which is interesting, because the diagram for a single grid interactive converter showed back to the utility at the same spot in the diagram. I would not read too much into it when it is inconsistent.
I see no reason for AC modules to be treated any differently from single GTIs, and I suspect the intent of the person who did that graphic was to reinforce that the AC modules could not just be connected to any available existing circuit.
 
david said:
I'm not going to agree that the inverter output circuits extend past the connection point (past the source disconnect) I do see why you guys it does. And based on that you do not believe any further direction to apply the source calculations to conductors and bussbars in series with the inverter output circuits to the utility service equipment is needed. Your position is you have to apply those calculations by utility inverter output circuits to all of the series equipment.
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Do you design PV systems for a living? I do, and I have done hundreds of them from a few kW to over a MW. Application/interpretation of the 120% rule the way I have described it is universal among all the AHJ's to whom I have submitted designs. You may twist in the wind over the language in the code, but I have had long conversations with utility engineers over this and similar issues, and I know how this stuff works. I don't know everything, but I know a lot.

The language which now is in 705.12 was relaxed a little to allow us to use 125% of the inverter output current in our calculations instead of the breaker ratings; in the past we had to round up an unnecessary second time. That, and ...(c) legitimized the AC combiner panels we had been using for years without solid justification. The laws of physics which are behind the 120% calculation certainly haven't changed. You CANNOT feed 100A of PV through a subpanel into a 200A/200A MDP. You can only feed 40A (125% of max inverter current) to it no matter if it is through a dedicated breaker or how many series subpanels you go through and what their ratings are. Period. It doesn't matter a whit what you call the conductors.

[/rant]
Gordon Gunn, BSEE, PE, NABCEP
 
david said:
I'm not going to agree that the inverter output circuits extend past the connection point (past the source disconnect)
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That is very odd, as it is right there in the definition: for other than a stand-alone system, "the conductors between the inverter and the service equipment".

Cheers, Wayne
 
OK, here's my 4 cents on the definition in 690:

2011 NEC 690.2 said:
Inverter Output Circuit. Conductors between the inverter and an ac panelboard for stand-alone systems or the conductors between the inverter and the service equipment or another electric power production source, such as a utility, for electrical production and distribution network
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The last part of that seems a little confusing, but here's how I break it down:

Only power source on site is the PV: this is a "stand-alone" system and is covered by the first phrase "Conductors between the inverter and an ac panelboard for stand-alone systems"

Only power sources on site are the PV and the utility: this is the usual case and is covered by the phrase "the conductors between the inverter and the service equipment".

Only power sources on site are PV and a local generator: you have no service equipment, but you have "another power production source". So the Inverter Output Circuit goes from the inverter to the generator.

Concurrent power sources are PV, the utility, and another power production source: you get to pick whether your Inverter Output Circuit goes to the utility service or to your other power production source.

Cheers, Wayne
 
P.S. The definition in 705.2 for "Utility Interactive Inverter Output Circuit" is basically the same, except that it excludes the case of "only power source is the PV", so the definition drops the "stand-alone system" phrase.

Cheers, Wayne
 
I apologize for the tone of the last thing I posted. I was having a trying day.
 
wwhitney said:
Only power source on site is the PV: this is a "stand-alone" system and is covered by the first phrase "Conductors between the inverter and an ac panelboard for stand-alone systems"

Only power sources on site are the PV and the utility: this is the usual case and is covered by the phrase "the conductors between the inverter and the service equipment".

Only power sources on site are PV and a local generator: you have no service equipment, but you have "another power production source". So the Inverter Output Circuit goes from the inverter to the generator.

Concurrent power sources are PV, the utility, and another power production source: you get to pick whether your Inverter Output Circuit goes to the utility service or to your other power production source.Cheers, Wayne
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A connection point to the service disconnect you kind of have to twick 705.12 and treat it as a line side of service equipment connection point
 

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wwhitney said:
Only power sources on site are the PV and the utility: this is the usual case and is covered by the phrase "the conductors between the inverter and the service equipment".Cheers, Wayne
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wwhitney said:
P.S. The definition in 705.2 for "Utility Interactive Inverter Output Circuit" is basically the same, except that it excludes the case of "only power source is the PV", so the definition drops the "stand-alone system" phrase.Cheers, Wayne
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Load side connection point
 

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I'm not sure what you are driving at. The "NO LOADS" you see everywhere simply means that you can't have any loads tapped into the conductors between an inverter and the first (closest to the inverter) OCPD between the inverter and the interconnection. The placement of that OCPD confuses some people; it's on the other end of the conductors from what is "normal" for power supplies. This is because it is not there to protect the conductors from the inverter; the inverter is a current limited device and cannot deliver enough current to endanger the conductors. The OCPD is there to protect the conductors from fault current coming from the utility.
 
david,
From what you quoted above...

Conductors between the inverter and an ac panelboard for stand-alone systems or the conductors between the inverter and the service equipment or another electric power production source, such as a utility, for electrical production and distribution network.
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Please read that blue part again.

To me that clearly indicates that the inverter output ends at the service equipment or (if the primary source is not a utility) at the disconnect for the other source, not the disconnect for the PV.

I really don't understand how you can misread this to say that the PV disconnect is the end of the inverter output. The diagrams you posted don't show that either, they show an open ended arrow towards the other source. (Stand-alone systems would not be the subject of discussion here.)

I've explained it several times and I'm pretty much going to stop now. :bye:
 
jaggedben said:
david,
From what you quoted above...

I really don't understand how you can misread this to say that the PV disconnect is the end of the inverter output. The diagrams you posted don't show that either, they show an open ended arrow towards the other source. (Stand-alone systems would not be the subject of discussion here.)

I've explained it several times and I'm pretty much going to stop now. :bye:
Click to expand...


Figure 690.1(A) Identification of Solar Photovoltaic System Components.
Notes
1. These diagrams are intended to be a means of identification for
Photovoltaic systems components, circuits, and connections
2. Disconnecting means required by 690, Part III are not shown.
3. System grounding and equipment grounding are not shown.
See Article 690, Part V



Figure 690.1(B) Identification of Solar Photovoltaic System Components in Common System Configurations.
Notes
1. These diagrams are intended to be a means of identification for
Photovoltaic systems components, circuits, and connections
2. Disconnecting means required by 690, Part III are not shown.
3. System grounding and equipment grounding are not shown.
See Article 690, Part V
4. Custom designs occur in each configuration, and some components
are optional

I do not see how you view it that way when the note 1. of the diagrams states the diagrams are intended to be a means of identification of the inverter output circuit.

There is an identifying arrow from the inverter output circuit ( title) to a circuit between two components in the stand alone system. And to a circuit coming from the inverter to the next component in the other diagram
 
ggunn said:
I'm not sure what you are driving at. The "NO LOADS" you see everywhere simply means that you can't have any loads tapped into the conductors between an inverter and the first (closest to the inverter) OCPD between the inverter and the interconnection. The placement of that OCPD confuses some people; it's on the other end of the conductors from what is "normal" for power supplies. This is because it is not there to protect the conductors from the inverter; the inverter is a current limited device and cannot deliver enough current to endanger the conductors. The OCPD is there to protect the conductors from fault current coming from the utility.
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.

Wasn’t Mr. Brooks in Mike Holts video who state the inverter output circuit is the no load portion of the system.
Isn’t he the person that was involved with writing the tap rule section of the 2014 Code?

In that video he states it is key to understanding these rules No Load
 
david said:
Figure 690.1(A) Identification of Solar Photovoltaic System Components.
Figure 690.1(B) Identification of Solar Photovoltaic System Components in Common System Configurations.
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Figure 690.1(B) "Interactive System" shows that the Inverter Output Circuit extends to the Electric Production and Distribution Network (EPDN) connection. So what's an EPDN? There's a definition in 690:

2011 NEC Article 690 said:
Electrical Production and Distribution Network. A power production, distribution, and utilization system, such as a utility system and connected loads, that is external to and not controlled by the photovoltaic power system.
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So basically it means the utility grid, or if you are large enough to maintain your own power production and distribution grid, your local grid.

The fact that the EPDN does not include the usual feeders and branch circuits for loads is reinforced by the Article 690 definition of Stand-Alone System:

2011 NEC Article 690 said:
Stand-Alone System. A solar photovoltaic system that supplies power independently of an electrical production and distribution network.
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A stand-alone system may have feeders and branch circuits, but it doesn't have an EPDN. That is, feeders and branch circuits alone do not make an EPDN.

Thus, for a site where the only power sources are a utility and PV production, the Inverter Output Circuit definition reduces to "Conductors between the inverter and the service equipment".

Cheers, Wayne
 
david said:
.

Wasn’t Mr. Brooks in Mike Holts video who state the inverter output circuit is the no load portion of the system.
Isn’t he the person that was involved with writing the tap rule section of the 2014 Code?

In that video he states it is key to understanding these rules No Load
Click to expand...
Well, OK, but you cannot have any loads on the conductors that run from the inverter to the first OCPD. If that OCPD is in a combiner/sub panel, you are allowed to have loads in that panel, assuming you are compliant with 705...(c). If that panel is fed by a breaker in another panel, 125% of the total inverter current in the sub counts toward the 120% rule in the MDP irrespective of the rating of the breaker feeding the sub from the MDP.

It used to be that in most jurisdictions you could not have any loads in the subpanel with the inverter breakers but they did not make you count the breaker feeding the subpanel toward the 120% rule, but this was not explicit in the NEC. 705...(c) cleared this up and legitimized AC Combiner panels.

OK, now I am officially blue in the face. :D
 
david said:
...There is an identifying arrow from the inverter output circuit ( title) to a circuit between two components in the stand alone system.
Click to expand...

Yes, stand alone systems have a somewhat different definition as quoted already in multiple previous posts. Stand alone systems are not what we are arguing about.

And to a circuit coming from the inverter to the next component in the other diagram
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Not true!! :happyno: The next component is not shown! It's just an arrow pointing to an indefinite ending point! :happyyes: That ending point is defined elsewhere in the code as 'the service equipment or another source ...', and there is nothing in the diagram that suggests there can't be other equipment in between.
 
david said:
.

Wasn’t Mr. Brooks in Mike Holts video who state the inverter output circuit is the no load portion of the system.
Isn’t he the person that was involved with writing the tap rule section of the 2014 Code?

In that video he states it is key to understanding these rules No Load
Click to expand...

He's talking about the branch circuit, not feeders and distribution. I'm not going to search the hour long video for the part you're talking about to see if he paraphrased or mispoke. But I would bet you $5 that he would agree with me. :p

E-mail him if you like. his e-mail is on his website (see bottom of page) http://brooksolar.com/contactus.html
 
jaggedben said:
Yes, stand alone systems have a somewhat different definition as quoted already in multiple previous posts. Stand alone systems are not what we are arguing about.



Not true!! :happyno: The next component is not shown! It's just an arrow pointing to an indefinite ending point! :happyyes: That ending point is defined elsewhere in the code as 'the service equipment or another source ...', and there is nothing in the diagram that suggests there can't be other equipment in between.
Click to expand...

jaggedben said:
He's talking about the branch circuit, not feeders and distribution. I'm not going to search the hour long video for the part you're talking about to see if he paraphrased or mispoke. But I would bet you $5 that he would agree with me. :p

E-mail him if you like. his e-mail is on his website (see bottom of page) http://brooksolar.com/contactus.html
Click to expand...

Ok, I took your advice and did Email Mr Brooks

Dear Mr. Brooks;
I was hoping to gain your insight to help clarify the point of termination for the Inverter Output Circuits for a load side connection point and specifically when that connection point originates in a load side connection at a subpanel. I have included the definition in 690.2 although my contention is really the definition in 705.2
I find the definition for inverter output circuits to be descriptive. The definition seems to simply describe the inverter output circuits under three conditions in 690.2
1. Stand-alone systems inverter to ac panel board (out side the scope of article 705)
2. Inverter to the service equipment. ( to the service equipment neither line side or load side connection point 705.12)
3. Inverter to another electric power production source, such as a utility ( in article 705.12 line side connection point)

Looking at the definition of service equipment intended to constitute the main control and cutoff of the supply and being connected to the load end of service conductors. I find the definition for inverter output circuits to be awkward at best to try and apply it to a load side connection point in article 705.12

I am being told by individuals that I would call experts in this field that the inverter output circuits include all conductors and bussbars from the load side connection point in a subpanel in series with the service disconnect for the utility, to the utility service equipment.

I find that to be awkward, that being the only time the inverter output circuits would be defined as part of load distribution conductors. I also find it awkward to be redefining conductors such as feeders to be inverter output circuit conductors.

I find the definition for inverter output circuits in 705.2 to be missing a description for a load side connection point. I am therefore unsure if this definition as given in 705.2 should be applied to a load side connection point.

I am not a professional graphics designer, I have included some graphics to try and help clarify what I am asking. Any opinion you have on clarifying where the inverter output circuit’s end on a load side connection point would be appreciated.

David
 
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