Protecton at the Inverter Output Circuit Source? E.g the inverter ( 690.9 )

[Anode]

I got a phone call from a plan reviewer recently, who was asking where the over current protection was, at the source, on our Solectria 28kW inverter. The call came after they had approved our plans, but this person was I guess just curious or second guessing their approval.

They pointed to NEC 2014 690.9 (A) and where I see the confusing exists in the last sentence highlighted in that paragraph, where it says, "shall be protected at the source from overcurrent."

I explained that I've got a ac/dc disconnect on that inverter, CCC's coming off the inverter sized appropriately, OCPD's in the panel board collecting the inverter output circuits, and a main pv disconnect after that, all sized for over current protection. Yet, he still insisted that the code wants protection at the source.

For something that seems so automatic for me, I was struggling to properly clarify his question. Some alternate interpretations here would be great.

 

[Pharon]

My interpretation has been that you want the OCPD protecting the inverter feeder from short circuit faults at the source where the highest contribution is. That place is at the other side of the feeder, closest to the utility. I thought this was in Article 690 somewhere, but I can't seem to find it.

I'm curious to see what others say about it.

 

[Pharon]

In 690.9, it says the following:

Circuits, either ac or dc,
connected to current-limited supplies (e.g., PV modules, ac output
of utility-interactive inverters), and also connected to sources
having significantly higher current availability (e.g., parallel
strings of modules, utility power), shall be protected at the source
from overcurrent.

It could be written clearer, but I think the source they're referring to (which I put in bold) is the utility, since it has a significantly higher current availability than the inverter.

 

[Carultch]

In 690.9, it says the following:



It could be written clearer, but I think the source they're referring to (which I put in bold) is the utility, since it has a significantly higher current availability than the inverter.

The authors of 690 should know that "source" is ambiguous when power can flow both directions.

 

[PVfarmer]

I explained that I've got a ac/dc disconnect on that inverter, CCC's coming off the inverter sized appropriately, OCPD's in the panel board collecting the inverter output circuits, and a main pv disconnect after that, all sized for over current protection. Yet, he still insisted that the code wants protection at the source.

I added the DC / AC note.
Sounds like you are connected line side?
I think the "source" is the utility too. It doesn't say "getting power from", just "connected to".

The PV inverters are connected to the grid- that's the source of "significantly higher current availability" that the PV inverters are supposed to be protected from.

The person who is:
asking where the over current protection was, at the source,

Seems to be asking about these:
OCPD's in the panel board collecting the inverter output circuits

Which are already there! Um...good luck!
Kind of sounds like they want breakers right at the inverter outputs, which is kind of odd.

New language was added to Section 690.9(A) to clarify that circuits of either ac or dc connected to current-limited supplies (such as PV modules (DC), ac output of utility-interactive inverters(AC)), and also connected to sources having significantly higher current availability (such as, parallel strings of modules (DC) and utility power (AC)), shall be protected at the source from overcurrent.
http://www.dli.mn.gov/ccld/pdf/fall14_NEC.pdf

 

[PVfarmer]

They pointed to NEC 2014 690.9 (A)

Try pointing at 705.12(D)(1)?
Looks pretty clear there to me. Maybe the same, (D)(3) also.

http://pvlabels.com/03-212-label/

 

[jaggedben]

The inverter is incapable of producing an overcurrent, so that's your protection from the inverter. It's its own OCPD.

For protection from the utility, you need a breaker or fuse.

 

[SolarChuk]

EH?

EH?

Wouldnt the source of a pv system be the sun?