non-fused for AC disconnect supply side tap

[CollinP.]

So I wanted to see if anyone could help me with this. I keep getting different things from city's. So when I submit a design with a supply side tab interconnection, some ask for a fused AC disconnect, others for a non-fused AC disconnect. would there be any reason to do one over the other?
Any help would be great.

 

[shortcircuit2]

So I wanted to see if anyone could help me with this. I keep getting different things from city's. So when I submit a design with a supply side tab interconnection, some ask for a fused AC disconnect, others for a non-fused AC disconnect. would there be any reason to do one over the other?
Any help would be great.

Shortcircuit and Fault protection from the Utility's AFC

 

[electrofelon]

You are going to need an OCPD there somewhere, so I dont really see what a non fused gets you. One possibility is you are using it for a utility disconnect requirement and have a fused disco or breaker elsewhere. The problem with non fused is the SCCR is only 10k unless series rated with other fuses.

 

[pv_n00b]

I can’t imagine the reasoning that would go into requiring a disconnect without fuses. I’d like to hear it though.

There are usually two reasons that drive me to use a fused disconnect:

1) 705 starting in 2014 requires the OCPD on a supply side interconnection to be within 10’ of of the service entrance.

2) Most unfused disconnects have have to be protected by an upstream OCPD to limit fault current. This is in the manufacturer's documentation. Since this information about unfused disconnects is in the manual and not on a sticker on the disconnect a lot of these are used incorrectly. Using a fused disconnect with a class R fuse usually gives an AIC rating of 100,000 to 200,000A, way more than I will ever need, and no upstream OCPD requirement.

 

[ggunn]

So I wanted to see if anyone could help me with this. I keep getting different things from city's. So when I submit a design with a supply side tab interconnection, some ask for a fused AC disconnect, others for a non-fused AC disconnect. would there be any reason to do one over the other?
Any help would be great.

Supply side interconnections need OCPD within 10' of the point of interconnection. Are you sure those instances where the city calls for a nonfused disco the systems are truly supply side interconnected? It's hard for me to accept that a utility would not require OCPD at or very near a supply side connection.

 

[PVfarmer]

What is up with this exception to 750.31? The service...what?

Exception: Where the overcurrent protection for the power
production source is located more than 3m ( 10') from
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.

That sounds a bit odd to me, the OCPD should be within 10' of..itself? :huh:

Isn't it saying:
"If the OCPD for inverter(s) is more than 10' from the service...(???), the inverter OCPD point is the service connection point"...??

some ask for a fused AC disconnect, others for a non-fused AC disconnect.

Shortcircuit and Fault protection from the Utility's AFC

One possibility is you are using it for a utility disconnect requirement and have a fused disco or breaker elsewhere. The problem with non fused is the SCCR is only 10k unless series rated with other fuses.

Around here, the non-fused is what the POCO wants (outside) and the fused switch is elsewhere for protection, and the fused can be seemingly not within 10 feet, going by the pdf below.

I can’t imagine the reasoning that would go into requiring a disconnect without fuses. I’d like to hear it though.
1) 705 starting in 2014 requires the OCPD on a supply side interconnection to be within 10’ of of the service entrance.
2) Most unfused disconnects have have to be protected by an upstream OCPD to limit fault current.

Supply side interconnections need OCPD within 10' of the point of interconnection.
It's hard for me to accept that a utility would not require OCPD at or very near a supply side connection.

I'm sure someone will disagree with me- I don't agree with myself here...
Seems to me code does not really require OCPD within 10' of a meter or j-box, and the POCO wants one next to the meter. (outside)
(Side note: an overhead "service entrance" where I am includes:OVERHEAD SERVICE CONDUCTORS, DRIP LOOP, O.H. SERVICE-ENTRANCE CONDUCTORS, SERVICE EQUIPMENT)

The reasoning in part I suppose would be so they don't have to get inside homes or businesses to flip the switch, perhaps both emergencies and maintenance?

750.31/exception says "service"- not entrance or conductors or where the point of interconnection is exactly.
So how can there be an exception to place something over 10 feet away which says that you have to put the same something within 10 feet? :huh:

That said, sometimes it is a good idea!
(I think this actually relates to eds' post about the 2 services somehow:
http://forums.mikeholt.com/showthread.php?t=182816 )

I mean... the bold part above of 705.31..."connected to the service." Period. The service...what?
It doesn't say service entrance....but...the service entrance conductors run from the meter to main (house) disconnect.
So when you add PV conductors to those supply side, and you are adding more supply side conductors, until you hit the first fused PV switch/breaker.

Here's a diagram with non-fused switch outside and fused inside:
(So I'm saying the fused switch doesn't have to be 10' from j-box, the j-box is *not* the point where the "power production" is connected to the service. The second, fused PV disco is that point)
https://www9.nationalgridus.com/non_html/DG_sample_1line_B.pdf

 

[PVfarmer]

https://www9.nationalgridus.com/non_html/DG_sample_1line_B.pdf

One important thing- that diagram is not exactly up to date.
The green part is saying the j-box in diagram isn't allowed any more.

Effective January 1, 2017
Notice for customers regarding Rhode Island Renewable Energy Growth (RE-Growth) dual meter installations
This notice serves to clarify the acceptable installation methodology for multiple meter installations related to Rhode Island’s Renewable Energy Growth (RE-Growth) program. This notice does not nullify or supersede National Grid standard requirements for meter installation. It is provided for additional clarification, specifically related to the unique installations of Rhode Island RE-Growth.

The following installation approaches are acceptable. Any other installation approach is not acceptable by National Grid. All installations are subject to review and approval by National Grid. Clarification on the topic will be added to the next scheduled revision of ESB 756.

Note: Due to the required service change for this program if your electrical meter is currently located inside it will need to be moved outside at your location to meet National Grid standards.

Overhead Service Installations

• At the home, provide single service from the weatherhead to a multi-gang meter socket, for installation of the multiple meters required for RE-Growth.
• At the home, provide parallel services from the weatherhead to individual meter sockets, for installation of the multiple meters required for RE-Growth.

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. Bifurcation of the service for the purposes of serving multiple meters related to RE-Growth is only acceptable at the weatherhead.

Underground Service Installations
Provide single service to house, which will feed a multi-gang meter socket, for installation of the multiple meters required for RE-Growth. Expansion joint is required for the feeder entering the meter socket, which is consistent with National Grid standard practice for meter installation.

Note: Due to the nature of underground service installations, a multi-gang meter socket is the only acceptable means of installation.

 

[shortcircuit2]

What is up with this exception to 750.31? The service...what?

Exception: Where the overcurrent protection for the power
production source is located more than 3m ( 10') from
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.

That sounds a bit odd to me, the OCPD should be within 10' of..itself? :huh:

Isn't it saying:
"If the OCPD for inverter(s) is more than 10' from the service...(???), the inverter OCPD point is the service connection point"...??







Around here, the non-fused is what the POCO wants (outside) and the fused switch is elsewhere for protection, and the fused can be seemingly not within 10 feet, going by the pdf below.





I'm sure someone will disagree with me- I don't agree with myself here...
Seems to me code does not really require OCPD within 10' of a meter or j-box, and the POCO wants one next to the meter. (outside)
(Side note: an overhead "service entrance" where I am includes:OVERHEAD SERVICE CONDUCTORS, DRIP LOOP, O.H. SERVICE-ENTRANCE CONDUCTORS, SERVICE EQUIPMENT)

The reasoning in part I suppose would be so they don't have to get inside homes or businesses to flip the switch, perhaps both emergencies and maintenance?

750.31/exception says "service"- not entrance or conductors or where the point of interconnection is exactly.
So how can there be an exception to place something over 10 feet away which says that you have to put the same something within 10 feet? :huh:

That said, sometimes it is a good idea!
(I think this actually relates to eds' post about the 2 services somehow:
http://forums.mikeholt.com/showthread.php?t=182816 )

I mean... the bold part above of 705.31..."connected to the service." Period. The service...what?
It doesn't say service entrance....but...the service entrance conductors run from the meter to main (house) disconnect.
So when you add PV conductors to those supply side, and you are adding more supply side conductors, until you hit the first fused PV switch/breaker.

Here's a diagram with non-fused switch outside and fused inside:
(So I'm saying the fused switch doesn't have to be 10' from j-box, the j-box is *not* the point where the "power production" is connected to the service. The second, fused PV disco is that point)
https://www9.nationalgridus.com/non_html/DG_sample_1line_B.pdf

ThepostissolongIcantgettoyourpoint?

 

[ggunn]

ThepostissolongIcantgettoyourpoint?

Agreed. Why post a simple statement when a page and a half of text with maybe a point in there... somewhere... will suffice?

 

[PVfarmer]

First point is, in 705.31: service _______.
What fills in the blank? I don't think that "entrance" works.

Supply side interconnections need OCPD within 10' of the point of interconnection.
1) 705 starting in 2014 requires the OCPD on a supply side interconnection to be within 10’ of of the service entrance.

And my other point is that there is quite clearly an exception that says the OCPD can be more than 10' from the point of connection/interconnection.
However, the meaning of the exception is not as clear as its existence.

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 _______.

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 ________.

 

[pv_n00b]

There is no fill in the blank, you might be trying to read too much into this. The Art. 100 definition is:

Service. The conductors and equipment for delivering electric
energy from the serving utility to the wiring system of the premises
served.

Art. 705.31 is referring to the intersection of the utility and premises wiring. But pretty much everyone accepts the service entrance equipment or service disconnect as a stand in for this, if in close proximity to the POCC, even when it’s not exactly the same point.

 

[ggunn]

And my other point is that there is quite clearly an exception that says the OCPD can be more than 10' from the point of connection/interconnection.
However, the meaning of the exception is not as clear as its existence.

[...]

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 ________.

It's pretty clear to me. If you cannot place the fused disco for your PV system within 10' of the point of interconnection you have to have current limiting devices on your conductors at the point of interconnection, which are in essence OCPD's, so it's not really much of an exception.

 

[PVfarmer]

There is no fill in the blank, you might be trying to read too much into this. The Art. 100 definition is:

Service. The conductors and equipment for delivering electric
energy from the serving utility to the wiring system of the premises
served.

Art. 705.31 is referring to the intersection of the utility and premises wiring. But pretty much everyone accepts the service entrance equipment or service disconnect as a stand in for this, if in close proximity to the POCC, even when it’s not exactly the same point.

I think the blank should be "entrance conductors", and the conductors between the fused PV switch and supply side j-box are those.
Technically, power is "exiting" the premises throught them, but...?

I mean...what about-
for delivering electric energy from the serving utility *or from the PV inverters* to the wiring system...

I realize that 705.31 is talking about adding a j-box for instance, to the conductors between the meter and main house panel section that Art.100 defines.

So if the j-box is the interconnection point, how can you add at or near it...
cable limiters or current-limited circuit breakers for each ungrounded conductor...
at the point where the electric power production conductors are connected to the service
when that point can be more than 10 feet away?

An example:
You have a meter on the outside of a house with service entrance conductors going into the basement, j-box added for PV.

There are panels on an out-building 50 feet away, and inverters inside it with their OCPDs, say two inverters into 30A breakers for each in a panel with a 60A main.
That is what the exception is about, more than 10' away from the service ____.

If there is a 60A fused PV switch on the outside of the outbuilding, you have service conductors from the outbuilding to j-box.

If the same 60A fused switch is within 10 feet of the meter, you only have service conductors from that switch to j-box, it doubles as the 27/7 POCO switch, and it's the point where PV output becomes service.

Another benefit of putting it <10' from j-box is being able to use smaller conductors for a long-ish run.

Now say the panels are on the house, inverters are in the basement, with a fused PV switch 5 feet from the supply side connection point.
Why would you put *another* fused switch outside for the POCO between the inverters and fused basement switch?

 

[PVfarmer]

If you cannot place the fused disco for your PV system within 10' of the point of interconnection

Where does it say *if you cannot*? It sort of sounds like "if you don't"...
And where's the "point of interconnection"?


690.56 Identification of Power Sources.
(B) Facilities with Utility Services and PV Systems.
Buildings or structures with both utility service and a PV
system shall have a permanent plaque or directory providing
the location of the service disconnecting means and the
PV system disconnecting means if not located at the same
location. The warning sign(s) or label(s) shall comply with
1 10.21 (B).

 

[PVfarmer]

It's pretty clear to me.

It's clear to me that the junction box/splice point on the supply side is not the interconnection point.
Here's why:

690.54 Interactive System Point of Interconnection.
All interactive system(s) points of interconnection with other
sources shall be marked at an accessible location at the
disconnecting means as a power source and with the rated
ac output current and the nominal operating ac voltage.

POIC = point of disconnecting means.
"After" the PV disco, those conductors are connected to the main service breaker, meter, and service xfmr with no OCPD protecting them.
It may be mentioned in the NEC, but the supply side j-box is in POCO territory.

90.2 Scope.
(A) Covered. This Code covers the installation of electrical
conductors, equipment, and raceways; signaling and
communications conductors, equipment, and raceways; and
optical fiber cables and raceways for the following:

(3) Installations of conductors and equipment that connect
to the supply of electricity...

 

[ggunn]

Where does it say *if you cannot*? It sort of sounds like "if you don't"...
And where's the "point of interconnection"?

Don't, can't, what's the difference? If the PV inverter output conductors are longer than 10' from the point of interconnection to the (fused) disco, then you need current limiters at the point of interconnection. The point of interconnection is the point where your PV conductors touch the unprotected conductors from the service. I deal with this stuff on a daily basis and it's not that complicated.

And yeah, I know that the code says "within 10 feet" and is ambiguous as to whether that means 10 feet between boxes or 10 foot long conductors, but the AHJ's I deal with go with the more conservative length of conductors interpretation.

Picking apart the language in the NEC looking for ambiguities is like shooting fish in a barrel; there are plenty of them because it is a document written by committees. Rather than getting tied up in knots by them, I prefer to build safe systems that pass inspection and move on. Most of the time, it's not that difficult.

 

[PVfarmer]

1 Don't, can't, what's the difference?

2 The point of interconnection is the point where your PV conductors touch the unprotected conductors from the service.

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.

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.

 

[PVfarmer]

And yeah, I know that the code says "within 10 feet" and is ambiguous as to whether that means 10 feet between boxes or 10 foot long conductors, but the AHJ's I deal with go with the more conservative length of conductors interpretation.

Picking apart the language ...

For one thing, there's no reason for us to be arguing- you are saying the code says "OCPD must be within 10 feet of POI".
I agree with you, but I don't think it is said clearly enough. (well I agree, but I think the OCPD *is* the POI, and it should be within 10' from the service entrance point, and it should be outside, but not necessarily connected to entrance conductors...)

Yes, I think there should be a fused PV disco outside *before* a load side connection too- why not?

I think it should say (not exactly these words, obviously):
"your fused disco switch for a supply side PV should be within 10 feet of the *exterior* service entrance conductors where the PV is connected to the utility supply and on-site loads, and within 10' of where the service enters the structure for a load side connection to an interior panel"

Second of all, picking apart the language is important- the thing about 10 feet- it doesn't mention inside/outside.

Makes sense to me-
a fused PV disco switch and supply side j-box should both be outside, and under 10' from each other.
a fused PV disco switch for a load side connection should be within 10' of where the service conductors enter for the main panel the PV is connected to.

Why 10', why not 5'?

 

[jaggedben]

Why should we care what you think if you're not stating any reasons for why the code should be different than it is?

The NEC does not require service equipment to be outside. It also does not require redundant overcurrent protection for a load side connection. Connections made in panelboard, whether load side or supply side, are usually done with a circuit breaker and thus do not need any more overcurrent protection. Connections made with splices or terminal blocks need to have overcurrent protection nearby, and a fused disconnect is the most common (but not the only) way to do this.

 

[PVfarmer]

Why should we care what you think if you're not stating any reasons for why the code should be different than it is?

The NEC does not require service equipment to be outside.

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?

Like this one for example, it's a non-fused disco required outside for a load side connection.
I certainly apologize if you haven't seen one before- here you go:
https://www9.nationalgridus.com/non_html/DG_sample_1line_A.pdf