PV only service

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I am working on a 1 MW PV installation which got me thinking about a few things. For the purpose of this discussion, assume the NEC applies here. I was having a discussion with a coworker about a few code violations the engineer made. One was that he didnt upsize the feeder EGC's proportionate to the ungrounded conductors which had been upsized for voltage drop. The coworker said there was an exception to that rule for PV and I stated but that the feeder wasnt part of that exception. Anyway, that got me thinking about this broader question: Is there anything different about a service or feeder that contains ONLY PV generation and no loads? I say no, except for indirect consequences such as 705.12(D)(3)(c). Similarly, is there anything special about a PV line side tap? I say no its just adding another set of service entrance conductors and an additional service disconnecting means correct? I see no purpose to 230.82(6). Does anyone disagree with this?
 
.....A correction/addition to the comment regarding the PV supply side connection being nothing more than an additional set of service entrance conductors and additional service disconnect already permitted in article 230: yes there is 705.31 but if they want to give a codified length distance for a set of service entrance conductors used for a power production source, so be it but I still say 230.82 is unnecessary and adds confusion.....
 

Smart $

Esteemed Member
Location
Ohio
... Is there anything different about a service or feeder that contains ONLY PV generation and no loads? I say no, except for indirect consequences such as 705.12(D)(3)(c). Similarly, is there anything special about a PV line side tap? I say no its just adding another set of service entrance conductors and an additional service disconnecting means correct? I see no purpose to 230.82(6). Does anyone disagree with this?
First off, when you state no loads, you have to consider that the grid in this instance is a load. Regardless, you are correct that it makes no difference.

It's been debated whether the disconnect is actually a service disconnecting means. I lean towards the "not" side of the debate. But as you bring up by inference, 230.82(6) would be unnecessary if it actually were a service disconnecting means... but then again, if it were a [no load] service disconnecting means, how would you determine the service [entrance] rating???
 
First off, when you state no loads, you have to consider that the grid in this instance is a load.

Funny you should mention that because that is another thing that came up the other day, the question of whether the utility should be connected to the line or load side of the disconnects. I thought nothing should change as its not direction of energy flow that matters but de-energizing the fuse blades, but Im not sure if there is explicit code reference I could cite if someone connecting the panelboard feeders to the line side


So in this aforemention installation, are there no service disconnects? How do I tell if the interconnection(s) are a supply side connection or a load side connection :)
 

Smart $

Esteemed Member
Location
Ohio
Funny you should mention that because that is another thing that came up the other day, the question of whether the utility should be connected to the line or load side of the disconnects. I thought nothing should change as its not direction of energy flow that matters but de-energizing the fuse blades, but Im not sure if there is explicit code reference I could cite if someone connecting the panelboard feeders to the line side


So in this aforemention installation, are there no service disconnects? How do I tell if the interconnection(s) are a supply side connection or a load side connection :)
Interesting point.

Connection to a utility is always a service, whether there are loads or not. So with no loads, and thus no service disconnecting means, by default, the PV System will be connected to the supply side.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Similarly, is there anything special about a PV line side tap? I say no its just adding another set of service entrance conductors and an additional service disconnecting means correct? I see no purpose to 230.82(6). Does anyone disagree with this?

I think your forgetting that "just adding another set of service entrance conductors" isn't allowed without 230.82(6). That's the purpose of it, to allow it. See 230.40 and how Exception 5 refers back to 230.82(6).

I suppose one could argue that 705.12(A) allows it by itself, but I'd prefer to see 230.82(6) stay there because the code is still vague about exactly how you are allowed to connect supply-side. For example, without 230.40 Ex. 5 and 230.82(6), I could see some AHJ arguing that the only way I can do a supply side connection is to get a new PV only service. That would be a disaster for my business.

BTW, we just had a thread about 690.45 and upsizing EGCs. It only applies to DC circuits.
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Interesting point.

Connection to a utility is always a service, whether there are loads or not. ...

Actually the definition of a service isn't written that way. I came very close to submitting a revision to it before the closing date, but decided not to because, frankly, I think it keeps our options more open.
 

Smart $

Esteemed Member
Location
Ohio
Actually the definition of a service isn't written that way. ...
Bar one word...
Service. The conductors and equipment for delivering electric
energy from the serving utility to the wiring system of
the premises served.

A rewrite might be...
Service. The conductors and equipment for delivering electric
energy from/to the serving utility to/from the premises wiring system.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Interesting point.

Connection to a utility is always a service, whether there are loads or not. So with no loads, and thus no service disconnecting means, by default, the PV System will be connected to the supply side.
Do you really want to install fuses on the hot side of the switch?
 

Smart $

Esteemed Member
Location
Ohio
But inverters do use a small amount of power.

So IMO...a PV system is a load...supplied by a service from a utility on grid interactive systems.
Actually they use no power from the utility as long as there is AC output from the inverter. At least when using basic electrical theory. Current cannot flow in two directions on the same wire at the same time. If the grid and inverter were slightly out sync', they could use a small amount of power from the grid... but they most definitely do when it is totally dark.

But if it helps your compliance with Code, you can develop any premise you want... :D
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I didn't say that... :?

If fused, they go on the PV side.

Perhaps I misinterpreted what you said. I was replying to this: "...the PV System will be connected to the supply side." The fuses on a disco are on the load side of the switch. Whether the disco is fused or not, the utility goes on the line/supply of the switch and the inverter goes on the load side.
 
I think your forgetting that "just adding another set of service entrance conductors" isn't allowed without 230.82(6). That's the purpose of it, to allow it. See 230.40 and how Exception 5 refers back to 230.82(6).

It is allowed by 230.40 ex 2 just like we do all the time for services with multiple service enclosures. Unless you are hung up on the "....supplying separate LOADS from one service drop...." part. Why not just get rid of the "supply side connection" mess, all it does is confuse things IMO. Its not a supply side connection. I guess it starts as one but we still need a disconnect and overcurrent protection like any other set of service entrance conductors so in the end its just another service disconnect with something connected after the service disconnect :?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Perhaps I misinterpreted what you said. I was replying to this: "...the PV System will be connected to the supply side." The fuses on a disco are on the load side of the switch. Whether the disco is fused or not, the utility goes on the line/supply of the switch and the inverter goes on the load side.
But if a CB used as a disconnect has LINE and LOAD markings it cannot be backfed, since there will always be the chance of an inverter side fault powered by POCO as well as power flow the other way when the GTI is operating.
 

Smart $

Esteemed Member
Location
Ohio
It is allowed by 230.40 ex 2 just like we do all the time for services with multiple service enclosures. Unless you are hung up on the "....supplying separate LOADS from one service drop...." part. Why not just get rid of the "supply side connection" mess, all it does is confuse things IMO. Its not a supply side connection. I guess it starts as one but we still need a disconnect and overcurrent protection like any other set of service entrance conductors so in the end its just another service disconnect with something connected after the service disconnect :?
There's an advantage to the way it is (but not PV only) that you are forgetting. The PV System disconnect (that you are calling a service disconnect) is not required to be grouped with any actual service disconnect. If you chamge to call it a service disconnect, then it would be required to be grouped with others. That said, I realize some POCO's and/or AHJ's may require it to be grouped anyway...
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
But if a CB used as a disconnect has LINE and LOAD markings it cannot be backfed, since there will always be the chance of an inverter side fault powered by POCO as well as power flow the other way when the GTI is operating.
Of course. Did someone mention a CB?
 
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