Quick EGC Question

[andykee]

Quick and easy one for anyone out there relating to "Sizing the EGC" from table 2501.22. Lets say I have 3 inverters feeding an AC Combiner with 3 60a breakers for each inverter and a main 200a breaker on top. Do I size my EGC from my DC Combiner off the 200a breaker in that box? Making it a 6AWG?

 

[Smart $]

Quick and easy one for anyone out there relating to "Sizing the EGC" from table 2501.22. Lets say I have 3 inverters feeding an AC Combiner with 3 60a breakers for each inverter and a main 200a breaker on top. Do I size my EGC from my DC Combiner off the 200a breaker in that box? Making it a 6AWG?

Not so easy, unless you meant AC combiner. If yes, then yes... unless that EGC is rather a combined EGC/GEC...

 

[andykee]

Just read on in the code book 250.122(c) for multiple circuits, if this is the case would my size be 60a? (ie sized off the largest OCPD protecting conductors in the raceway) This is an EGC running through 3 11000tl-us transformerless inverters, then continuing to the AC combiner box.

 

[Smart $]

The EGC's from the DC combiner to the inverters are considered separately from the EGC's from the inverters to the AC combiner.

DCC-->Inverter: based on fuse rating. If no fuse, 690.45 of 2014 NEC added text to clarify where no fusing, an assumed overcurrent device rated at the PV maximum circuit current.

Inverter-->ACC: based on Inverter OCPD rating (60A in your case).

 

[Carultch]

Quick and easy one for anyone out there relating to "Sizing the EGC" from table 2501.22. Lets say I have 3 inverters feeding an AC Combiner with 3 60a breakers for each inverter and a main 200a breaker on top. Do I size my EGC from my DC Combiner off the 200a breaker in that box? Making it a 6AWG?

If there is an overcurrent device, whether it is required or not, you size the EGC per table 250.122.

If there is not an overcurrent device, you size the EGC by the maximum continuous current. Which ends up being calculated as 1.25*total Isc. That is the rule as of 2014. In previous editions, it used to be direct total Isc instead. Whichever value it ends up being, you look it up in table 250.122.

 

[jaggedben]

Just read on in the code book 250.122(c) for multiple circuits, if this is the case would my size be 60a? (ie sized off the largest OCPD protecting conductors in the raceway) This is an EGC running through 3 11000tl-us transformerless inverters, then continuing to the AC combiner box.

If the EGC is run with the three 60A circuits, it only has to be sized for the circuit with the largest OCPD. So, 60A, and you can use a #8.

You probably shouldn't be running the EGC through each inverter unless it is looping up to each one from a gutter or something. The EGC is required to run with the circuit conductors.