690.31(E) and inverter output circuits

Status
Not open for further replies.

mcnut

Member
Location
Florida
I am having a discussion at the office reguarding 690.31(E)Direct-Current PV Source and Output Circuits inside a building. The difference in opinion we are having is with the "output circuits of a utility interactive inverter". One of us thinks this is refering to AC or DC inverter outputs and the other thinks it refers to DC only inverter outputs. I want to be subjective so I am not saying what position I have taken, but can anyone help us out? Thank you in advance.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
690.31(E) does not apply to inverter output circuits. The language you quote ("utility interactive inverter") does not appear in that section of the 2011 code.

690.2 defines "photovoltaic source and output circuits" as the DC circuits from the solar panels (singular or paralleled). Those are the only circuits to which 690.31(E) applies.

An inverter cannot have DC output circuits, by definition.
 

mcnut

Member
Location
Florida
(E) Direct-Current Photovoltaic Source and OutputCircuits Inside a Building.​
Where direct-current photovoltaicsource or output circuits of a utility-interactive inverterfrom a building-integrated or other photovoltaic system arerun inside a building or structure, they shall be contained inmetal raceways, or metal enclosures, from the point of penetrationof the surface of the building or structure to thefirst readily accessible disconnecting means. The disconnecting
means shall comply with 690.14(A) through (D).


We are still on the 2008
 
Last edited:

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Doesn't this article mean both?

The panel wires going to the inverter are DC,"Where direct-current photovoltaic source" the wires after the invertor are AC, "output circuits of a utility-interactive inverter from a building-integrated or other photovoltaic system" .

If either pass through a building or structure..."they shall be contained in metal raceways, or metal enclosures, from the point of penetration of the surface of the building or structure to the first readily accessible disconnecting means."

And as jaggedben noted,
An inverter cannot have DC output circuits, by definition.
 
Last edited:

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I am having a discussion at the office reguarding 690.31(E)Direct-Current PV Source and Output Circuits inside a building. The difference in opinion we are having is with the "output circuits of a utility interactive inverter". One of us thinks this is refering to AC or DC inverter outputs and the other thinks it refers to DC only inverter outputs. I want to be subjective so I am not saying what position I have taken, but can anyone help us out? Thank you in advance.
As someone else pointed out, inverter outputs are never DC. If you look at figure 690.1(B) for the interactive system, you'll see what they are talking about when they refer to the "...direct current photovoltaic... output circuits of a utility-interactive inverter...". It's the output circuit from a combiner box, which is DC, and is actually the input to the inverter. All DC inside a building needs to be in metal conduit. That language was clarified in the 2011 code.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Man, that 2008 language is horrible, I had forgotten. But look at the title of the section you quoted: "(E) Direct-Current Photovoltaic Source and Output Circuits Inside a Building." That tells you what it applies to, in my opinion, and doesn't include inverter output circuits.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Doesn't this article mean both?

The panel wires going to the inverter are DC,"Where direct-current photovoltaic source" the wires after the invertor are AC, "output circuits of a utility-interactive inverter from a building-integrated or other photovoltaic system" .

As I said, the language is horrible, but since "direct-current photovoltaic source" isn't a full noun-phrase then the full noun phrase must be "direct-current photovoltaic source or output circuits...". Therefore all the circuits referred to by this sentence are DC circuits. That they are 'of a utility-interactive inverter" was either confusing or unnecessary to state, and the 2011 code took that part out.
 

mcnut

Member
Location
Florida
Well the specific application we are having the discussion about involves enphase inverters. For those who might not know these are mounted right on the rack with the modules. The cables that are used with the enphase system comply with all the disconnecting means requirements on the roof (690.14(D)(1-2)). Now the question is, do the conductors from the combiner box on the roof to the readily accessible disconnect need to me in a metal raceway? These conductors would be inverter output conductors (240v 1ph) and run inside the building to backfeed a breaker in the existing electrical panel, being the readilly accesable disconnect. Another point is 690.14(D)(3) requires the additional AC disconnect to comply with 690.14(C). 690.14(C) requires a disco means to be readily accesible on the outside of the building or inside the nearest point of entrance of the system conductors, with an exception to installations that comply with 690.31(E) allowing disco means to be remote from the point of entry of the system.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Well the specific application we are having the discussion about involves enphase inverters. For those who might not know these are mounted right on the rack with the modules. The cables that are used with the enphase system comply with all the disconnecting means requirements on the roof (690.14(D)(1-2)). Now the question is, do the conductors from the combiner box on the roof to the readily accessible disconnect need to me in a metal raceway? These conductors would be inverter output conductors (240v 1ph) and run inside the building to backfeed a breaker in the existing electrical panel, being the readilly accesable disconnect. Another point is 690.14(D)(3) requires the additional AC disconnect to comply with 690.14(C). 690.14(C) requires a disco means to be readily accesible on the outside of the building or inside the nearest point of entrance of the system conductors, with an exception to installations that comply with 690.31(E) allowing disco means to be remote from the point of entry of the system.
In the case of Enphase microinverters, 690.31(E) does not apply at all. If it's not DC, it's not addressed by 690.31(E), no matter how obtuse the language is. My opinion is that the AC lines from an Enphase microinverter are the same as any other AC multiwire branch circuit in a building, but you code warriors are certainly free to prove me wrong. :D
 
Last edited:

mcnut

Member
Location
Florida
My opinion is that the AC lines from an Enphase microinverter are the same as any other AC multiwire branch circuit in a building

I agree. This is just one of those poorly written codes. Horrible use of of "or", or needs commas or something. Thank you for your input.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I agree with ggunn. And I have installed Enphase in several jurisdictions where we used NM cable inside the building as one might for any AC branch circuit.

As I said in another recent thread, in my opinion 690.14 does not apply to AC disconnects except where it specifically refers to them. Requirements for AC disconnecting means are in 705. That's just my interpretation though. :p

Another point is 690.14(D)(3) requires the additional AC disconnect to comply with 690.14(C). 690.14(C) requires a disco means to be readily accesible on the outside of the building or inside the nearest point of entrance of the system conductors, with an exception to installations that comply with 690.31(E) allowing disco means to be remote from the point of entry of the system.

Yeah, this might be difficult to get around if your AHJ is really a stickler for the letter of the code. I doubt the CMP really thought through what they were doing there.
 

SolarPro

Senior Member
Location
Austin, TX
McNut,

Your getting good responses, so I won't repeat what's already been said. If it helps to have some of this in writing, you can refer to this article:

http://solarprofessional.com/article/?file=SP5_4_pg58_Fisher

While there are some meaningful differences between the way the NEC treats a microinverter system versus and AC module system, these differences are mainly on the dc side of the system. So the content in this article that relates to ac wiring, also applies to enphase systems.

FWIW: Here's a link to a John Wiles article that covers many of the same topics, but is published by the IAEI, which may carry more weight with your inspector:

http://www.iaei.org/magazine/2010/03/the-microinverter-and-the-ac-pv-module/
 

Zee

Senior Member
Location
CA
Yes, referenced code refers to DC circuits ONLY.
They were saving words and made it confusing.

Romex is fine for AC output of enphase or string inv.
Has been for 10 years.

(as for on roof, of course you need conduit outside array if exposed)

Finally, I caution you use the expression "combiner box" for DC only. Altho, hey,if load centers combining enphase branch circuits are now referred to as such, i gotta get with the times.

Just to be OBJECTIVE.:roll:
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Yes, referenced code refers to DC circuits ONLY.
They were saving words and made it confusing.

Romex is fine for AC output of enphase or string inv.
Has been for 10 years.

(as for on roof, of course you need conduit outside array if exposed)

Finally, I caution you use the expression "combiner box" for DC only. Altho, hey,if load centers combining enphase branch circuits are now referred to as such, i gotta get with the times.

Just to be OBJECTIVE.:roll:

Enphase are racking-attached microinverters -- Romex is rated to 60C which is not fine for a roof.

The term I hear more often for AC "combiner boxes" is "aggregation panels". Though I've got to tell you, I'd love to find me a 100A main breaker panel that's not huge or 200A.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Enphase are racking-attached microinverters -- Romex is rated to 60C which is not fine for a roof.

...and Romex is fine for some other section of the inverter output circuit that's inside the building.

I've done this several times. Conduit from the J-box on the roof to another J-box in the attic, then Romex from the attic down to the service panel.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
...and Romex is fine for some other section of the inverter output circuit that's inside the building.

I've done this several times. Conduit from the J-box on the roof to another J-box in the attic, then Romex from the attic down to the service panel.

Yup, that'll do it.
 
Status
Not open for further replies.
Top