GEC required

[csoc64]

For a roof mounted DC utility interactive system, is a GEC required on the roof array. The inverter is located in the basement of the house. My understanding is that the GEC is for the Inverter, and the balance of the normally non-current carrying metal parts (panels and rails) are bonded with a EGC.

 

[Smart $]

For a roof mounted DC utility interactive system, is a GEC required on the roof array. The inverter is located in the basement of the house. My understanding is that the GEC is for the Inverter, and the balance of the normally non-current carrying metal parts (panels and rails) are bonded with a EGC.

DC utility interactive system???

Generally speaking, your understanding is correct. Can't be more specific as your details are fairly vague.

 

[jaggedben]

csoc64,

You've got it basically correct, although take a look in the 2008 code (if it applies to you) at 690.47(D). A grounding electrode and GEC is required near the array if the conductors do not come right down to the inverter. (This requirement went away in the 2011 code, but will be back in the 2014 code.) In any case, all the equipment can be bonded to this GEC with with one or more EGCs.

Smart$, in the industry we conventionally refer to "DC systems" for string or central inverters and "AC systems" for microinverters or AC modules. Not really a technical distinction most of the time but it's clear to me what he means.

 

[csoc64]

csoc64,

You've got it basically correct, although take a look in the 2008 code (if it applies to you) at 690.47(D). A grounding electrode and GEC is required near the array if the conductors do not come right down to the inverter. (This requirement went away in the 2011 code, but will be back in the 2014 code.) In any case, all the equipment can be bonded to this GEC with with one or more EGCs.

Smart$, in the industry we conventionally refer to "DC systems" for string or central inverters and "AC systems" for microinverters or AC modules. Not really a technical distinction most of the time but it's clear to me what he means.

Not sure I follow you when you say "if the conductors do not come right down to the inverter".
Here's my layout...14 panels mounted on roof, then will be running #10 conductors through EMT, across roof and down side of house to Inverter which is mounted on the outside of house. Total conduit run is approx. 45 feet. From there, the AC power will go into the house and into the main panel, which is a total of 10 feet from where the inverter is mounted. I guess what I am asking is if the #8 GEC needs to go all the way to the array, or does it just need to go from the inverter to the main panel, with a EGC running from the array to the inverter.
Currently working of 2011 NEC, however Massachusetts will adopt 2014 on Jan 1, 2014.

 

[Smart $]

...

Smart$, in the industry we conventionally refer to "DC systems" for string or central inverters and "AC systems" for microinverters or AC modules. Not really a technical distinction most of the time but it's clear to me what he means.

I assumed as much. Simply wanted clarification. I'm currently working a nuke and thus in don't-assume-anything mode...

 

[Smart $]

Not sure I follow you when you say "if the conductors do not come right down to the inverter".
... I guess what I am asking is if the #8 GEC needs to go all the way to the array, or does it just need to go from the inverter to the main panel, with a EGC running from the array to the inverter.
Currently working of 2011 NEC, however Massachusetts will adopt 2014 on Jan 1, 2014.

I believe he means that if the grounding conductor is not run with circuit conductors (i.e. an EGC) then it would have to be a GEC (which BTW, wouldn't alleviate the requirement for the EGC with the circuit conductors).

 

[ggunn]

I believe he means that if the grounding conductor is not run with circuit conductors (i.e. an EGC) then it would have to be a GEC (which BTW, wouldn't alleviate the requirement for the EGC with the circuit conductors).

I think he means that if the inverter is not located directly down (or nearly so) from the array, you need to run a GEC from the array to a ground rod. I don't know that to be true, necessarily, but that's what I thought he was saying.

 

[jaggedben]

Not sure I follow you when you say "if the conductors do not come right down to the inverter".

I think he means that if the inverter is not located directly down (or nearly so) from the array, you need to run a GEC from the array to a ground rod. I don't know that to be true, necessarily, but that's what I thought he was saying.

Here is the actual language of 690.47(D), in the 2008 code.

"Additional Electrodes for Array Grounding. Grounding electrodes shall be installed in accordance with 250.52 at the location of all ground-and pole-mounted photovoltaic arrays and as close as practicable to the location of roof-mounted photovoltaic arrays. The electrodes shall be connected directly to the array frame(s) or structure. The dc grounding electrode conductor shall be sized according to 250.166. [etc.]"

Emphasis added. It's pretty vague if you ask me.

Here's my layout...14 panels mounted on roof, then will be running #10 conductors through EMT, across roof and down side of house to Inverter which is mounted on the outside of house. Total conduit run is approx. 45 feet. From there, the AC power will go into the house and into the main panel, which is a total of 10 feet from where the inverter is mounted.

I would say that if the grounding electrode is close to the main, you're not obligated to put a new electrode closer to the array. But I'm not your AHJ. :lol: FWIW, I've seen very few AHJs who seem to know about this requirement or enforce it. And I don't think it makes much sense to enforce it on residential systems, unless it's a very large home with the array on the opposite end of the house from the electrical service.

I guess what I am asking is if the #8 GEC needs to go all the way to the array, or does it just need to go from the inverter to the main panel, with a EGC running from the array to the inverter.
Currently working of 2011 NEC, however Massachusetts will adopt 2014 on Jan 1, 2014.

Under 2011 it definitely just needs to go from inverter to main. I haven't looked at the actual language in the 2014 code and whether it is at all different than the 2008 version, I just heard the requirement is coming back. That part about being "connected directly" could be interpreted any number of ways, I think.

 

[ggunn]

Under 2011 it definitely just needs to go from inverter to main. I haven't looked at the actual language in the 2014 code and whether it is at all different than the 2008 version, I just heard the requirement is coming back. That part about being "connected directly" could be interpreted any number of ways, I think.

Here in Austin Energy's jurisdiction, for commercial systems at least, they want a ground rod at the inverter(s).