Plaque providing location of pv system disconnect- NEC 690.56 (B), 2011

Zee

Senior Member
Location
CA
2011 NEC 690.56(B)
Buildings or structures with both utility service and a photovoltaic
system shall have a permanent plaque or directory providing the
location of the service disconnecting means and the photovoltaic
system disconnecting means if not located at the same location.

Can i get yay or nay's as to whether this applies to dc discos only or to a pv ac disco?
(to me it is clear: any mention of "pv system" indicates the dc side)
 

SolarPro

Senior Member
Location
Austin, TX
This language hasn't changed in many years. Every AHJ I have worked in accepted the interpretation that "PV system disconnecting means" refers to the disconnect on the ac output of the inverter or inverter system. In our directories, we always identified the location of the ac disconnecting means for the PV system and only occasionally the location of dc service disconnects. (Imagine a directory showing all of the dc disconnect locations for a 1MW subarray. That would be a big and hard to read placard. :blink:)
 

Zee

Senior Member
Location
CA
SOLARPRO,
I appreciate the response. The reason i ask is that for over a decade, i understood it just like you do, as the ac disco.....

1.
However, ( given our recent mega thread :) on a loosely related topic)
the term "PV system disconnecting means" seems reserved by the NEC for dc discos.... at least within just 690.13-15.
Would you agree with that? Before i go on with my reasoning:p

2.
Then consider: the term "PV SYSTEM V" is defined as DC V in 690 DEFINITIONS. If that is an equation, then you subtract V from both sides..... and we get PV system = DC system.

3.
Finally, what i really would tend to believe is that 690.56 was in fact intended to apply to ac discos......... but they used the confusing term, "pv sys disco means" that really only meant DC disco elsewhere.
I am easy.
 
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GoldDigger

Moderator
Staff member
Then consider: the term "PV SYSTEM V" is defined as DC V in 690 DEFINITIONS. If that is an equation, then you subtract V from both sides..... and we get PV system = DC system.
I think that you actually have to divide both sides of the equation by V, which is OK as long as V is not zero. :)
 

Smart $

Esteemed Member
Location
Ohio
The best way to comprehend these requirements (IMO ;)) is to determine the transition from PV system to a distribution system (i.e. supply rather than source) or from PV system to another source (such as a supply-side service connection). There is no instance where a source, PV or otherwise, can supply loads without a disconnecting means at the transition.

A PV system could potentially be a hybrid, i.e. supplying power to both AC and DC loads. The plaque would have to indicate the location of both [transitional] disconnects, along with any service disconnects.
 

SolarPro

Senior Member
Location
Austin, TX
@ Zee: Yes, I agree. 690.13, which uses terms like "PV system disconnect" and "PV system disconnecting means," specifically refers to ungrounded dc conductors. So let's say you installed a disconnect where dc circuits entered a building per 690.31(G), 690.56 would require that disconnect to have a placard and/or directory. And that is consistent with what we used to do in the field. (And since this applies to building or structures, it doesn't apply to a multi-MW plant except to the extent that each substructure might have a labeled disco.)

I've only skimmed the mega-thread you referred to, but it makes sense that requirements pertaining to the ac side of a PV system would now be covered in Article 705. In fact, it is 705.10 that requires a directory identifying the location of all electric power sources on the premises.

Sorry for the incorrect info earlier. I hadn't ever given this much thought before. (Probably because 690.14 was such a mess that it lent itself to many possible interpretations. In that sense, the new Code sections are an improvement.)
 
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Smart $

Esteemed Member
Location
Ohio
@ Zee: Yes, I agree. 690.13, which uses terms like "PV system disconnect" and "PV system disconnecting means," specifically refers to ungrounded dc conductors. So let's say you installed a disconnect where dc circuits entered a building per 690.31(G), 690.56 would require that disconnect to have a placard and/or directory. And that is consistent with what we used to do in the field. (And since this applies to building or structures, it doesn't apply to a multi-MW plant except to the extent that each substructure might have a labeled disco.)

I've only skimmed the mega-thread you referred to, but it makes sense that requirements pertaining to the ac side of a PV system would now be covered in Article 705. In fact, it is 705.10 that requires a directory identifying the location of all electric power sources on the premises.

Sorry for the incorrect info earlier. I hadn't ever given this much thought before. (Probably because 690.14 was such a mess that it lent itself to many possible interpretations. In that sense, the new Code sections are an improvement.)
Now that you mention it, I had not considered the possibility that a PV system conductors ahead of the PV System Disconnect(s) could compliantly enter a building.

I still fail to see why everyone so adamantly wants to push any AC disconnect onto requirements of other sections. Where do you go when you have a stand-alone AC system???
 

GoldDigger

Moderator
Staff member
Now that you mention it, I had not considered the possibility that a PV system conductors ahead of the PV System Disconnect(s) could compliantly enter a building.

I still fail to see why everyone so adamantly wants to push any AC disconnect onto requirements of other sections. Where do you go when you have a stand-alone AC system???
If it is standalone instead of utility interactive, it becomes just another non-utility power source which requires a disconnect somewhere as it enters the building wiring system. Not quite sure which articles to apply though.
 

jaggedben

Senior Member
I've been making my points about 690.14 in the other 'mega-thread'....I'll just limit myself to the following here.

If the point of the plaque is to notify someone who wishes to de-energize all circuits inside a building, then the plaque ought to denote any or all of these:
1) the DC disconnect if the dc conductors enter the building
2) the rapid shutdown switch required in the new 690.12, if applicable.
3) any AC disconnect for the PV connected directly to service entrance conductors (whether you call it a 'service disconnect' or not).
4) any AC disconnect for a system with stand-alone capabilities

There really isn't a safety reason I can think of for it to denote load-side AC disconnects just because they are remote from the service disconnecting means.
 

SolarPro

Senior Member
Location
Austin, TX
Agreed. It will be interesting to see how some of these requirements change once you have touch-safe PV modules, which is the ultimate goal of 690.12. As 690.12 is written now, it effectively makes a dc service disconnect upon entry to a building redundant.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
@ Zee: Yes, I agree. 690.13, which uses terms like "PV system disconnect" and "PV system disconnecting means," specifically refers to ungrounded dc conductors.
I know I am preaching to the choir here, but it would be oh so helpful if and when the NEC is referring to exclusively DC disconnects it would say so explicitly instead of relying on the reader figuring it out from context.
 
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