supply side PV connection

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I believe with most POCO's where two or more meters are on one account, each meter is itemized separately. With net metering, it is just one meter, one reading value. But you are correct in that the net balance for multiple meters is calculated.
Yes, it's virtual net metering.
 

jaggedben

Senior Member
The problem is regulatory, not physical. For example California's virtual net metering is written such that all meters on a VNM account must be on the same service. So even though that is a perfect example of where you might think 230.2 should be invoked, you wouldn't be able to use it.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
The problem is regulatory, not physical. For example California's virtual net metering is written such that all meters on a VNM account must be on the same service. So even though that is a perfect example of where you might think 230.2 should be invoked, you wouldn't be able to use it.
Got it. Virtual net metering (or rather, something akin to it) is legal in Texas.
 

mpd

Senior Member
I thought everybody might find this interesting, this was the response from NFPA to our DCA in reference to 3 wire or 4 wire supply side connection,



Thank you for your email concerning the National Electrical Code@.

After consulting with the team here are NFPA we are in agreement that the PV system disconnect should not be bonded, an insulated grounded conductor would be required and the equipment grounding conductor carried back to the point of connection.

Regards,

Gil Moniz

Senior Electrical Specialist

National Fire Protection Association

I Batterymarch Park

Quincy, MA 02169-7471

617-770-3000
 

iwire

Moderator
Staff member
Location
Massachusetts
I thought everybody might find this interesting, this was the response from NFPA to our DCA in reference to 3 wire or 4 wire supply side connection,



Thank you for your email concerning the National Electrical Code@.

After consulting with the team here are NFPA we are in agreement that the PV system disconnect should not be bonded, an insulated grounded conductor would be required and the equipment grounding conductor carried back to the point of connection.

Regards,

Gil Moniz

Senior Electrical Specialist

National Fire Protection Association

I Batterymarch Park

Quincy, MA 02169-7471

617-770-3000
Thanks for sharing that.
 

Smart $

Esteemed Member
Location
Ohio
I thought everybody might find this interesting, this was the response from NFPA to our DCA in reference to 3 wire or 4 wire supply side connection, ...
Yet another informal interpretation. Also need query to obtain proper context of reply.


After consulting with the team here are NFPA we are in agreement that the PV system disconnect should not be bonded, an insulated grounded conductor would be required and the equipment grounding conductor carried back to the point of connection.
Do you realize all this does is shift the bond from in the disconnect enclosure to the "point of connection" enclosure? It is still a bonding of the PV System EGC(/GEC) to the Service grounded conductor.

The way I see it, they are in agreement as an easy out for the disconnect to not be regarded as a service disconnect.
 

c_picard

Senior Member
Location
USA
The way I see it, they are in agreement as an easy out for the disconnect to not be regarded as a service disconnect.
Right on. I'm really not sure why there is so much opposition to calling it (or at least treating it) as a service disconnect (one of many allowed, btw).

For fun, check out 230.82(5), and then (6). Why would we work so dang hard to avoid the language we see in (5)? (For now, let's just ignore the use of the word "taps" *cringe*).

"...if provided with service equipment and installed in accordance with requirements for service-entrance conductors."

If anyone is genuinely interested in putting this debate to rest in 2020, PM me. I'd like to collaborate on some fixes.
 

iwire

Moderator
Staff member
Location
Massachusetts
Right on. I'm really not sure why there is so much opposition to calling it (or at least treating it) as a service disconnect (one of many allowed, btw).

Here is one persons opinion. It should not be called a service disconnect because it is different. It has two way current flow.

I really think it should be called co-generation disconnect or something like that.
 

c_picard

Senior Member
Location
USA
Here is one persons opinion. It should not be called a service disconnect because it is different. It has two way current flow.

I really think it should be called co-generation disconnect or something like that.
Totally agree. The reality is we're looking at a new normal. The grid is changing in a fundamental way, and "service" can't continue to mean what it used to. There are far reaching ripple effects...things we take for granted like placing OCPDs at the "source" are becoming much more complicated.

Getting this sorted out will be critical to the future of code enforcement, and this is not hyperbole.

My opinion has always stemmed from the understanding that we must consider the fault current from all sources of supply. All the reasons we need to bond the grounded conductor at service equipment should apply to this disconnect as well, due to the presence of utility originated fault currents. If that fault current is as dangerous as everyone thinks it is, we should probably follow the same rules.
 

c_picard

Senior Member
Location
USA
To continue the thought, the existing service disconnect can't really be called a service disconnect either, because it's source of supply is no longer exclusively the utility.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
And the name distinction is important to the extent that bi-directional energy flow makes a difference.
If we are going that route maybe we should also distinguish between the disconnect for PV which inherently shuts down when grid power goes away and that for other co-generation which typically requires a network protection relay or other external protective equipment?
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
One thing I think we can all agree on (maybe!) is that the central issue here is that Distributed Generation (PV, et al.) throws new variables into a complex system of interrelated rules that were refined over many years without it. Every rule change designed to accommodate DG has ramifications to other rules, and those ramifications result in ambiguities and conflicts which need to be worked out. Add to that the fact that the technology for PV (in particular but not necessarily exclusively) is rapidly evolving and every code cycle has to address issues that didn't exist the previous time the NEC was revised.

As a PV instructor I studied with in my early experience in the field was fond of saying, "Welcome to the frontier."
 

mpd

Senior Member
I agree it is definitely not a service disconnect, but I did not have a problem with the 3 wire or 4 wire supply side PV connection, my question has been if you want to wire it as a service disconnect does the NEC prohibit it, I still don't think either method should fail but I do respect NFPA"s ruling and if that what it has to be to be code compliant I am fine with it. It still does not make sense to me a 4 wire supply side PV connection connected to a 3 wire SEU service entrance cable. I do agree this section could use some work to make.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I agree it is definitely not a service disconnect, but I did not have a problem with the 3 wire or 4 wire supply side PV connection, my question has been if you want to wire it as a service disconnect does the NEC prohibit it, I still don't think either method should fail but I do respect NFPA"s ruling and if that what it has to be to be code compliant I am fine with it. It still does not make sense to me a 4 wire supply side PV connection connected to a 3 wire SEU service entrance cable. I do agree this section could use some work to make.
IMO your best bet is to make an appointment for a preconstruction meeting with the AHJ and ask how they want it done. They may not care, but the two AHJ's I deal with most have definite and opposing views on the matter, and neither will pass a system designed/installed by the rules of the other.
 

jaggedben

Senior Member
To continue the thought, the existing service disconnect can't really be called a service disconnect either, because it's source of supply is no longer exclusively the utility.
:thumbsup:

...which is I why I'd simply advocate that the definition of service be changed.

And the name distinction is important to the extent that bi-directional energy flow makes a difference.
If we are going that route maybe we should also distinguish between the disconnect for PV which inherently shuts down when grid power goes away and that for other co-generation which typically requires a network protection relay or other external protective equipment?
Hear hear. The first type is very much just another boring old AC disconnect and should be treated as such in most respects, especially warning signs. Treating it differently is 'crying wolf' with respect to the second type.
 
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