non-fused for AC disconnect supply side tap

[ggunn]

1 Can't means- you aren't allowed to *or* weren't able to.
Don't means- you do not have to, and did not.

Again, it makes no difference. It either is or it isn't. Why it is or isn't is irrelevant. When I do it it's because I can't for some reason; it's a whole lot simpler and less expensive to put the fused disco less than 10' away from the point of interconnection (which is NOT the disco) and be done with it, but if there's no room on the equipment wall for the disco I have to do something else. If I were to choose to put it somewhere else for whatever reason, I could, as long as I put current limiters at the POI.

2 And that point would be at the PV OCPD. There are PV conductors on one side, unprotected conductors on the other.
They really never touch, you have to be able to disconnect the two. There's a breaker or fused switch between them.

If the PV inverter output conductors are longer than 10' from the point of interconnection to the (fused) disco,

So there's the complication- how can something be more than 10 feet from itself?

I see the PV output connectors as connected *at* the point of interconnection *to* the fused disco, there's no way they can be 10' from it when connected to it.

You are free to interpret the code any way you want, and good luck with that. The way the rest of the world interprets it, however, is that the point of interconnection is where the PV conductors touch the service conductors. There is no "complication", and the fact that it appears to be such a glaring contradiction to you should suggest to you that there is maybe something wrong with your interpretation.

If you want to tie yourself in knots over what you think the code says (when it doesn't, IMO), go ahead, but it seems pretty clear to me. I have hundreds of PV systems under my belt and I have never run into an inspector that looks at it the way you insist upon doing.

IMO you are trying to turn something simple into a Gordian Knot. It ain't that complicated, really.

 

[PVfarmer]

Seriously, y'all.

The thread is called: non-fused for AC disconnect supply side

I have posted links to pdfs from my local POCO showing non-fused discos required for *both* supply side and load side connections.

And you're acting like I have 2 heads.

Lighten up?

 

[ggunn]

Seriously, y'all.

The thread is called: non-fused for AC disconnect supply side

I have posted links to pdfs from my local POCO showing non-fused discos required for *both* supply side and load side connections.

And you're acting like I have 2 heads.

Lighten up?

No AHJ is going to insist that I have no OCPD between my POI and my inverter if it's a supply side interconnection. If it's a supply side interconnection there must be OCPD within 10' of the POI, and the POI is NOT the disco.

 

[PVfarmer]

No AHJ is going to insist that I have no OCPD between my POI and my inverter if it's a supply side interconnection. If it's a supply side interconnection there must be OCPD within 10' of the POI, and the POI is NOT the disco.

How could you possibly think I am saying an AHJ would say there should be "no OCPD between POI and inverter"...?
Typical internet, we're arguing despite not understanding each other...

You said-
the point of interconnection is where the PV conductors touch the service conductors.

I say, sure, that's the fused switch!

According to NatGrid and code, the "service conductors" are on the grid side of the meter.
There is no way you would connect PV there!
You connect supply side PV to the "service entrance conductors", and the AC PV disco is (I say) connected to the "load end of the service conductors".

These 3 definitions are from NEC 2014 Art. 100, they are also verbatim here in Nat Grid's greenbook ( https://www9.nationalgridus.com/non_html/shared_constr_esb750.pdf ):

Service Conductors, Overhead.
The overhead conductors between the service point and the first point of connection
to the service-entrance conductors at the building or other
structure.

Service-Entrance Conductors, Overhead System.
The service conductors between the terminals of the service
equipment and a point usually outside the building, clear of
building walls, where joined by tap or splice to the service
drop or overhead service conductors.

Service Equipment.
The necessary equipment, usually consisting
of a circuit breaker(s) or switch(es) and fuse(s) and
their accessories, connected to the load end of service conductors
to a building or other structure, or an otherwise designated
area, and intended to constitute the main control and cutoff of
the supply.

(there are zero NEC definitions for "point" or "interconnection" and this from NatGrid, the POA is up on the side of a house, then the service conductors lead to say the meter, and then service entrance conductors go from meter to service equipment)

Point of Attachment:
The location of the service drop conductors to a building or structure provided
by the Customer and installed to maintain clearances specified by the NEC (Article 230) and by the
Company’s requirements. (Service conductors are supported by mechanical attachment to the
building or structure.)


705.12(D) does mention "interconnection", and it sure sounds clear to me that the fusible disco is the interconnection point for inverters.
?
(1) Dedicated Overcurrent and Disconnect. The source
interconnection of one or more inverters installed in one
system shall be made at a dedicated circuit breaker or fusible
disconnecting means.

 

[jaggedben]

What reason more than "it is sort of unclear" do ya want? He even agreed with me...

Does code tell you what to do when equipment is in fact required to be outside for a load side connection?
Shouldn't it?

What do you mean by 'tell you what to do'? Remember that 90.1 says "This Code is not intended as a design specification or an instruction manual for untrained persons." The code tells us either what is specifically required or what is specifically prohibited (or not, i.e. permitted). It is not supposed to tell us the best way to do something.

In your example you've got an unrelated utility requirement. It's up to you to figure out how to meet that requirement as well as the code requirements. The code cannot account for every local requirement.

 

[PVfarmer]

What do you mean by 'tell you what to do'?

In your example you've got an unrelated utility requirement.

My 2 examples are both examples of what the OP is asking about.

And 'what to do'-I mean if someone wanted to put in a 3000w chandelier in a restaurant or an electrical outlet in a house or a PV system on a houseboat, the code tells one what conductors and breakers to use, among other things. (Not 100% sure about specifics re: houseboat)

You also said it yourself:
The code tells us either what is specifically required or what is specifically prohibited (or not, i.e. permitted).

What is required = what you do.

It tells you what you are supposed to and are allowed to do, and also what you are not allowed to do.
I know that fact.

The code also apparently shares some exact language with various POCO's requirements.

However, the code specifically says to put PV OCPD at the "point of interconnection", and does not specifically say where or what that POI is.

I mean, we seem to have 2 ideas going here of where/what the POI is, so perhaps more specific would be good.

 

[shortcircuit2]

There is a definition in fuel cells on POCC...

 

[SolarPro]

Is this really that hard?

Outside the context of Article 705, the point of common coupling is where the utility service ends and the premises wiring begins.

Within the context of Article 705.31, the point of connection is not the point of common coupling for the utility service but rather for the inverter; it is "the point where the electric power production source conductors are connected to the service;" this point is by definition ahead of the service disconnecting means but is almost always downstream from the point of common coupling for the utility service.

Right?

So you gotta put your OCPD within 10' of "the point where the electric power production source conductors are connected to the [utility] service." Bob's your uncle.

If this doesn't make sense, take a few minutes to read all of the definitions in Article 100 that contain the word "service." The service conductors extend into the premises wiring. When the utility made the connection to my house, they didn't connect to the Austin Energy meter or to the main service disconnect, right? We had to build some infrastructure on our site that is essentially part of their service. I'd argue and the utility would probably agree that the POCC for the overhead utility service is where the linemen made splices ahead of our weatherhead; the premises wiring between these splices and the main breaker, including the utility meter, is still part of the service, even though we built it.

 

[PVfarmer]

Is this really that hard?

If this doesn't make sense, take a few minutes to read all of the definitions in Article 100 that contain the word "service." The service conductors extend into the premises wiring.... I'd argue and the utility would probably agree that the POCC for the overhead utility service is where the linemen made splices ahead of our weatherhead; the premises wiring between these splices and the main breaker, including the utility meter, is still part of the service, even though we built it.

The service conductors extend into the premises wiring....

I'd say the service conductors are part of the premises wiring, but they don't extend to the indoors. From inside to outside is service entrance conductors.

Service-Entrance Conductors, Overhead System. The
service conductors between the terminals of the service
equipment and a point usually outside the building,

Here are my thoughts about all the definitions of service:
http://forums.mikeholt.com/showthread.php?t=183120&page=3&p=1819836#post1819836

As far as I know, in the premises wiring definition, the service point is at the weatherhead, on the grid side of drip loop, and the power source is PV.
Diagram on pg. 29 here: ( https://www9.nationalgridus.com/non_html/shared_constr_esb750.pdf )

Premises Wiring (System).
Interior and exterior wiring, including power, lighting, control, and signal circuit wiring
together with all their associated hardware, fittings, and
wiring devices, both permanently and temporarily installed.
This includes (a) wiring from the service point or power
source to the outlets where there is no service point.
Such wiring does not include wiring internal to appliances,
luminaires, motors, controllers, motor control centers,
and similar equipment.
Informational Note: Power sources include, but are not
limited to, interconnected or stand-alone batteries, solar
photovoltaic systems, other distributed generation systems,
or generators.

I agree with this-
this point is by definition ahead of the service disconnecting means but is almost always downstream from the point of common coupling for the utility service.

And I think the point is at the load end of the service conductors or the service entrance conductors, where they connect to the PV OCPD, not at the j-box.

So it's not complicated, but it is hard to find anyone who will agree...
If you have to put PV OCPD within 10', why is there an exception that says...you don't?

705.31 Location of Overcurrent Protection. Overcurrent
protection for electric power production source conductors,
connected to the supply side of the service disconnecting
means in accordance with 705.12(A), shall be located
within 3m (lOft) of the point where the electric power
production source conductors are connected to the service. (that point is a junction box)

Informational Note: This overcurrent protection protects
against short-circuit current supplied from the primary
source(s) of electricity.

Exception: Where the overcurrent protection for the power
production source is located more than 3m( 10') from the
point of connection for the electric power production
source to the service, cable limiters or current-limited circuit
breakers for each ungrounded conductor shall be installed
at the point where the electric power production
conductors are connected to the service. (in the j-box?? at a splice? how does that work? :huh

the premises wiring between these (weatherhead) splices and the main breaker, including the utility meter, is still part of the service, even though we built it.

And the wiring to the PV OCPD from the supply side j-box is part of the service, not the PV output.

 

[PVfarmer]

Is this really that hard?

it is "the point where the electric power production source conductors are connected to the service;"

So you gotta put your OCPD within 10'

If this doesn't make sense,

It is *really* simple.
If y'all want to define the j-box as the POI, meaning "the point where the electric power production source conductors are connected to the service"
I'd call it "the point where the conductors from the PV OCPD are connected to utility and load conductors", although "service" does = utility and load conductors.

But still, I don't think the exception in 705.31 makes sense.
If "at the point" means what y'all are saying....why would one be required put limiters or breakers IN the j-box?
If anyone has any reason why that's sensible, I'd love to hear them!

Why not replace these parts with:
"supply side conductors for the PV output"

"an additional service rated breaker or fused switch"
..shall be installed...
"within 10 feet of the point" where the...

"supply side conductors from the additional service rated PV breaker or fused switch"
...are connected to the service.

"The service" does run all the way from- POCO xfmr to the first OCPD(s) in service equipment.

Exception: Where the overcurrent protection for the power
production source is located more than 3m(10') from the
point of connection for the electric power production
source to the service, cable limiters or current-limited circuit
breakers for each ungrounded conductor shall be installed
at the point where the electric power production
conductors are connected to the service.

So:
Exception: Where the overcurrent protection for the power
production source is located more than 3m(10') from the
point of connection for the supply side conductors for the PV output
to the service, an additional service rated breaker or fused switch
shall be installed within 10 feet of the point where the
supply side conductors from the additional service rated PV breaker or fused switch are connected to the service.

 

[jaggedben]

...
And I think the point is at the load end of the service conductors or the service entrance conductors, where they connect to the PV OCPD, not at the j-box.
...

I don't think anyone is agreeing with you on this. I'll take my stab at simplifying it...

When you get to the point where the conductors come together from three directions at once - 1) utility, 2) PV, and 3) other premises wiring - that is the location of your supply side connection.

 

[PVfarmer]

When you get to the point where the conductors come together from three directions at once - that is the location of your supply side connection.

Where does the code say that?

If that is what it says, the 705.31 exception is telling us- when you put the PV OCPD more than 10' from "the point", you then must put a breaker at that point with conductors coming from 3 directions.
A 3-way breaker is a new one on me.

 

[SolarPro]

I don't think anyone is agreeing with you on this. I'll take my stab at simplifying it...

When you get to the point where the conductors come together from three directions at once - 1) utility, 2) PV, and 3) other premises wiring - that is the location of your supply side connection.

Exactly.

 

[SolarPro]

FWIW:

Section 705.31 “Location of Overcurrent Protection”

This new section limits the length of unprotected conductors in supply-side interconnections to 10 feet, due to safety concerns. According to a substantiation provided by CMP No. 4 in the ROP: “Often, when connections are made to, or ahead of, existing service-entrance equipment, space limitations do not allow for a disconnecting means with overcurrent protection to be adjacent to the service entrance equipment and still have proper working clearances. Consequently, many of the required disconnects with overcurrent protection are being installed remote from the service entrance equipment.”

Though subject to fault current from the utility, these conductors are not protected by the utility transformer’s primary OCPD(s). The CMP concludes: “A fault on these conductors will likely result in a violent, explosive conductor vaporization and potential equipment damage or complete burn down.” The unanimous decision to limit the unprotected conductor length to 10 feet mitigates this safety hazard.

Where the overcurrent protection for the parallel power production equipment is located more than 10 feet from the point of connection, an exception allows the use of cable limiters to provide short-circuit protection. Note that these cable limiters must be installed “at the point where the electric power production conductors are connected to the service.” A cable limiter is different than a fuse in that it isolates a conductor in response to short-circuit current only and does not provide overload protection. Due to space constraints, it may prove easier to install cable limiters at a service entrance in accordance with this exception rather than install a fused disconnecting means within 10 feet.

The addition of Section 705.31 brings the guidance for PV supply-side connections into closer agreement with requirements in Article 230 pertaining to service disconnecting means. For example, Section 230.70(A) requires that service disconnecting means be located at “a readily accessible location outside of a building or inside nearest the point of entrance of the service conductors.” Section 230.91 further requires that overcurrent protection be integral to or immediately adjacent to the service disconnecting means. Note that where disconnecting means for PV power production sources are located within 10 feet of the main service disconnecting means, they could be used, in conjunction with contactor combiners or other equipment, to initiate rapid shutdown for PV systems on buildings.

Excerpt from: Understanding the NEC 2014 and Its Impact on PV Systems

 

[PVfarmer]

FWIW:

Where the overcurrent protection for the parallel power production equipment is located more than 10 feet from the point of connection, an exception allows the use of cable limiters

Thanks for the article.
The exception does not "allow" the use- it *requires* the use.
cable limiters or current-limited circuit breakers for each ungrounded conductor shall be installed at the point...

This is kind of a big problem the more I think about it. I've never considered limiters, don't like the idea really.
If the inverters are more than 10 feet away, with OCPD for them where they are, I would put an additional fused PV switch as close to the 3-way j-box as possible, (already allowed when not additional by 705.31) and use the same size conductors as the main service between that switch and j-box.

Funny thing is, supply side j-boxes aren't even allowed by NatGrid in RI anymore.
Note: Installation of a single service from the weatherhead to a junction box mounted on the side of the house, which would subsequently serve individual meter sockets is not acceptable.

https://www9.nationalgridus.com/narragansett/business/energyeff/4_interconnection-process.asp

So, where's that "point of interconnection" in this diagram?

 

[jaggedben]

Where does the code say that?

It is the dictionary definition of 'connecting' an electrical circuit in parallel.

If that is what it says, the 705.31 exception is telling us- when you put the PV OCPD more than 10' from "the point", you then must put a breaker at that point with conductors coming from 3 directions.

A cable limiter or similar is NOT the same as an OCPD. It provides high current short circuit protection only.

 

[SolarPro]

Thanks for the article.
The exception does not "allow" the use- it *requires* the use.
cable limiters or current-limited circuit breakers for each ungrounded conductor shall be installed at the point...

Which is exactly what the authors go on to say: "Note that these cable limiters must be installed..."

The Code requires you to put OCPD within 10' of the POC, but in the Exception provides an allowance (a different set of requirements) for situations where that is not possible.

Like it or not, it is what it is. Good luck.

 

[ggunn]

I'd say...

I give up; I'm not reading all that. I know how it works, I know what to call it, and I know what the inspectors I deal with will pass and what they won't. These word games are a waste of time, so I'm not playing any more.

 

[PVfarmer]

1 It is the dictionary definition of 'connecting' an electrical circuit in parallel.

2 A cable limiter or similar is NOT the same as an OCPD. It provides high current short circuit protection only.

3 When you get to the point where the conductors come together from three directions at once - 1) utility, 2) PV, and 3) other premises wiring - that is the location of your supply side connection.

4 The Code requires you to put OCPD within 10' of the POC, but in the Exception provides an allowance (a different set of requirements) for situations where that is not possible.

Well golly, since a limiter isn't an OCPD, when you put one in the j-box, there's still no OCPD within 10 feet...hmm.

1
Not sure if that was supposed to be humorous.
When you get to the point where the conductors come together from three directions at once - that is the location of your supply side connection.

There is no dictionary on earth that says that.

2
I have to honestly say I think it's weird the way you keep telling me stuff that I know, and ignoring my perfectly legit points.

3
Great. And when you have a supply side setup with dual meters- your "point" no longer exists.

4
The code requires OCPD within 10 feet for safety, but the exception requires not-an-OCPD (see jb, #2 above) within the j-box, and drops the whole OCPD within 10 feet thing.
It simply doesn't seem safe.

The POCO requires an outdoor 24/7 switch adjacent to meter. (If the meter is inside, we are now required to move it outside for supply side)
A limiter sure isn't a switch, and a current-limiting breaker is, but does no one any good when inaccessible inside a j-box.

Here's what I'm not gonna do-
"Hi, NatGrid? I'm calling about that PV. Yes, the supply side connection. You know that 24/7 switch you require adjacent to the meter? Some people on the internet said forget about that silly switch, and to pop some limiters in the j-box and we're good to go. Cool?"
Then they'd every right to act like I have two heads.

Here's the same pic as before, but one meter and j-box. I didn't change what the conductors are called. Is there a specific section of code that says what I'm calling service conductors to the PV OCPD are actually PV output conductors?
I'd love to see it.
Re: the previous pic with dual meters- where should the limiter go there? At the meter terminals? Nope.

 

[jaggedben]

...
Not sure if that was supposed to be humorous.
When you get to the point where the conductors come together from three directions at once - that is the location of your supply side connection.

It was meant entirely seriously.

Great. And when you have a supply side setup with dual meters- your "point" no longer exists.

Yes it does. It's within the meter enclosure. Look above the meters in your drawing for the three way junction.

"Hi, NatGrid? I'm calling about that PV. Yes, the supply side connection. You know that 24/7 switch you require adjacent to the meter? Some people on the internet said forget about that silly switch, and to pop some limiters in the j-box and we're good to go. Cool?"

Nobody here told you that can ignore a utility's extra requirement because it's not also contained in the NEC. The particular utility requirement your citing basically means the cable limiter option is useless because you either have space for a disconnect - which can be fused - or you can't meet their requirements. However, only some utilities have such requirements...

Is there a specific section of code that says what I'm calling service conductors to the PV OCPD are actually PV output conductors? I'd love to see it.

No, there isn't, I'll grant you that whether those conductors are considered service conductors or not is quite controversial, there's been a number of long debates about that on this forum. HOWEVER, I do not agree that this leads to ambiguity with regard to 705.31. The point of connection to the service is still the 3-way junction point. That's what a point of connection means for a parallel connected electrical circuit.

Re: the previous pic with dual meters- where should the limiter go there? At the meter terminals? Nope.

Yes, at the meter terminals if possible.
For your example with one meter and a j-box, the j-box would have to have some kind of terminal bars or other provisions for attaching cable limiters.

Note that just because the code permits something in principle does not mean you're going to be able to do it with any given equipment without violating other parts of the code. The meter socket or J-box ould have to have the required space for conductors and provisions for connecting cable limiters that don't violate the listing of anything.