PV install question

Walt73

Member
I occasionally install PV equipment which is covered in article 690. I am struggling over the interpretation of article 690.31 (E). In the NEC 2011 edition, it reads Where dc photovoltaic source or output circuits from a building-integrated or other photovoltaic system are run inside a building or structure, they shall be contained in metal raceways, Type MC metal-clad cable that complies with 250.118(10).......
On the systems I install the DC source voltage from the panels goes to an inverter which turns that voltage to AC at the panel. The voltage from the panels is AC from that point to the first disconnect. Since the inverter is panel mounted, would a metal raceway of somekind be necessary inside a building or structure?
 
I occasionally install PV equipment which is covered in article 690. I am struggling over the interpretation of article 690.31 (E). In the NEC 2011 edition, it reads Where dc photovoltaic source or output circuits from a building-integrated or other photovoltaic system are run inside a building or structure, they shall be contained in metal raceways, Type MC metal-clad cable that complies with 250.118(10).......
On the systems I install the DC source voltage from the panels goes to an inverter which turns that voltage to AC at the panel. The voltage from the panels is AC from that point to the first disconnect. Since the inverter is panel mounted, would a metal raceway of somekind be necessary inside a building or structure?
This is NOT my area of expetise (if I even have one)... but it would seem to me just reading what you wrote, that the operative terms here are "dc source or output circuits". That leads me to believe (just off the cuff) that they may require MC from the cell to the inverter, or even to any dc load you may be feeding, but since everything after the inverter is AC, this text no longer seems to apply after that point. I'm sure you'll get a difinitive answer on this shortly. everyone seems to be interested in PV's anymore, including me:grin:
 

drive1968

Senior Member
If you are referring to Enphase inverters, the company uses NM in their example installation literature. Because the conversion to AC has already occurred at the micro-inverter, MC or EMT is not required after that point.
 

Walt73

Member
Thanks a ton guys, that's what I was figuring but it's nice to be affirmed. BTW, it is an enphase installation.
 

Walt73

Member
So, Smart $,
First of all, thanks for the reply. I read article 690.6, after reading the (A) and (B) sections, I am confused. Does that exempt the installer from the wiles of article 690.31 (E) in this application?
 
If you are referring to Enphase inverters, the company uses NM in their example installation literature. Because the conversion to AC has already occurred at the micro-inverter, MC or EMT is not required after that point.
Agreed.I believe 690.6 only refers to ac modules and you wouldn t fall under this code because they are dc modules with a micro inverter. How do you guys feel about those enphase micro-inverters anyway? I remember when I first heard of them I thought it would be a game changer, until I installed a system and found it very cumbersome and the data monitoring I felt wasn t very efficient. That could all be because the roof had a 60 degree pitch though.
 
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Smart $

Esteemed Member
So, Smart $,
First of all, thanks for the reply. I read article 690.6, after reading the (A) and (B) sections, I am confused. Does that exempt the installer from the wiles of article 690.31 (E) in this application?
It does, if I understand your description correctly... which is that you have "ac modules"... which is the term the NEC uses for PV panels with integrated inverters.
 

rgomes26

Member
I've inspected quite a few enphase systems. Since the output of the enphase inverter is ac there is no requirement to enclose the conductors that are inside the building in a metallic raceway.

I like the enphase systems because you're dealing with ac from the array out. Seems like a much safer product. Since they are built and listed to UL1741 if the utility power is disconnected you no longer have current in the conductors from the array to the ac point of connection.
 

kingpb

Senior Member
It does, if I understand your description correctly... which is that you have "ac modules"... which is the term the NEC uses for PV panels with integrated inverters.
I can't completely agree with that statement after looking at Figure 690.1(A). Although it is consistent with 690.2 which defines modules as "A complete, environmentally protected unit consisting of solar cells, optics, and other components, exclusive of tracker, designed to generate dc power when exposed to sunlight."

Seems that the NEC has some inconsistency in their definitions.
 

Smart $

Esteemed Member
I can't completely agree with that statement after looking at Figure 690.1(A). Although it is consistent with 690.2 which defines modules as "A complete, environmentally protected unit consisting of solar cells, optics, and other components, exclusive of tracker, designed to generate dc power when exposed to sunlight."

Seems that the NEC has some inconsistency in their definitions.
Last sentence of 690.1 states, "These systems may have ac or dc output for utilization." Also, please refer to lower diagram of Figure 690.1(A). There is no dc wiring external to each module. The key here is not that dc power is generated, but rather that ac power is output from the module... thus substantiation for the existence of 690.6. Otherwise, how would 690.6 ever be of any significance?
 
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tallgirl

Senior Member
The OP's question only applies to DC SOURCE circuits, not to AC output from any AC device, whether it's a string inverter, micro-inverter or battery-backed inverter.

The Enphase inverters make AC, and the DC connections don't pass through a building, so no requirement for a metallic raceway. If someone, for some twisted reason, decided to route the array output conductors into a building they'd have to be in a metallic raceway, but since most installers hang them underneath the panel, no such requirement.

As regards "AC Modules", a DC panel and attached micro-inverter is NOT NOT NOT an "AC Module". The only AC modules I know of are made by ExcelTech and are a manufacturer integrated panel and inverter than meets the NEC description. There is no DC connection -- the inverter is physically (and somewhat permanently) attached to the back of the panel in an environmentally secure, etc. fashion, not just bolted to the racking and attached with a rat's nest of cabling.
 

jaggedben

Senior Member
Those who responded earlier to this thread are correct that the AC outputs of a micro-inverter system are not required to be in metal conduit merely because they are solar (as would be required if they were DC solar source or output circuits).

The catch with this question, however, is that Enphase installations require a grounding electrode conductor. The installation of the GEC is subject to 250.64(B) and this seems to mean that you should either run a #8 GEC in conduit, or upsize the GEC (which is otherwise on required). In my experience I have yet to see an AHJ object to a solid #8 GEC run in addition to NM as long as this was only done inside walls. However I'm not sure what the argument would be if an AHJ objected to this.

...
As far as AC modules vs. DC modules, the use of a micro-inverter does not turn a module into an AC module. The inverter has to be integrated into the module to have an AC module: that is the inverter comes with the module, under a single listing. There are currently no AC modules on the market yet, but the Enphase M215 is designed to be integrated in this way (as well as be used as a separate micro-inverter), as are some other announced-but-not-yet-delivered micro-inverter products.
 

raider1

Senior Member
Staff member
Please read 690.6 Alternating-Current (ac) Modules.
Agreed.I believe 690.6 only refers to ac modules and you wouldn t fall under this code because they are dc modules with a micro inverter. How do you guys feel about those enphase micro-inverters anyway? I remember when I first heard of them I thought it would be a game changer, until I installed a system and found it very cumbersome and the data monitoring I felt wasn t very efficient. That could all be because the roof had a 60 degree pitch though.
It does, if I understand your description correctly... which is that you have "ac modules"... which is the term the NEC uses for PV panels with integrated inverters.
I can't completely agree with that statement after looking at Figure 690.1(A). Although it is consistent with 690.2 which defines modules as "A complete, environmentally protected unit consisting of solar cells, optics, and other components, exclusive of tracker, designed to generate dc power when exposed to sunlight."

Seems that the NEC has some inconsistency in their definitions.
Last sentence of 690.1 states, "These systems may have ac or dc output for utilization." Also, please refer to lower diagram of Figure 690.1(A). There is no dc wiring external to each module. The key here is not that dc power is generated, but rather that ac power is output from the module... thus substantiation for the existence of 690.6. Otherwise, how would 690.6 ever be of any significance?
After taking with a senior engineer with Enphase their product is not an AC Module and therefore 690.6 does not apply. They stated that they are hoping to have a product out within a year that will qualify as an AC module.

Also with the Enphase inverters, 690.14(D) applies to the micro inverters and 690.14(D)(3) requires a disconnecting means to be installed in accordance with 690.14(C)(1) which requires the disconnecting means to be located at a readily accessible location outside the building or inside nearest the point of entrance of the conductors. The exception to 690.14(C)(1) permits the readily accessible disconnect to be located remote from the point of entrance of the conductors provided that the conductors are contained in a metal raceway or MCAP Cable.

Chris
 
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