[RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters

[Aladdin Solar]

We will be installing a 40KW grid-tied PV system that uses PV modules wired in parallel as per the module manufacturer -- so it's a high amperage, low voltage system on the DC side. 2 branches of about 3KW of parallel wired modules each come together onto a DC bus. The DC branch conductors are sized as 2AWG.

The inverter system provided by the manufacturer consists of a number of UL1741 single phase microinverters that all are powered off of the low voltage DC bus. So there's a bunch of microinverters in parallel, combined output is single phase power.

Those microinverters have a ground lug labeled "GEC". You know where this is going...

Assuming we are following NEC 690.47(C)(3), we'll be treating this ground as GEC and following all the GEC rules. My understanding is that because the DC conductors within the array are 2AWG (NEC 250.166(B), we will need to connect all 12 branches and 6 DC buses with continuous 2AWG and bring it all the way back 300' to where the AC GEC bond is located. We're getting a lot of pushback from the electrical sub and even some disagreement from the module manufacturer on this--no one's ever seen a grounding conductor of this size being required for this application.

Please don't get too bogged down with understanding the low voltage, parallel module spec and the massive number of microinverters involved. What I'm looking for is confirmation that I am properly understanding how the NEC GEC requirements apply, especially to the GEC size.

Charlie Pickard
NABCEP Certified PV Installation Professional T
Aladdin Solar, LLC



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