[RE-wrenches] grounding the Enphase inverter

[Kirk Herander, VSE]

My AHJ is making me ground the Enphase inverters AND use a separate
equipment ground for modules / mounting rails.

The panel frames are grounded to mounting rails via WEEBS, rails are
grounded together using WEEB lay-in lugs and copper wire, this ground wire
makes its way to AC panel gnd bar, where it is connected to ground rod via
grounding electrode conductor, as normal.

AHJ insists I also install dedicated continuous ground wire from each
Enphase inverter gnd clip directly to the building GEC or to the ground rod
itself. Mind you, the inverter enclosure, to which the gnd clip is attached,
is already grounded to the mounting rails via WEEBs. So what I have done is
created a parallel ground between the mounting rails and the GEC, a.k.a a
ground loop, a.k.a. a current divider. Short circuit current from the
Enphase is going to be split between the two paths to ground.

The only way this grounding scheme makes any sense to me is if the inverters
were totally isolated from the rails using a non-conductive tape or washer
between the rail and inverter at point of attachment. Just removing the
WEEBS would not isolate the two. 
My AHJ is basically trying to apply the grounding rules of a string inverter
(dedicated gnd directly from inverter to GEC) to a micro-inverter, but I
feel this method, aside from redundancy and T $ M, is little short in the
"best practice" or "safest" categories.

I'd be interested in other takes on this. Thanks.




Kirk Herander
Vermont Solar Engineering
802.863.1202
NABCEP(tm) Certified Solar Installer
NYSERDA-eligible Installer
VT Solar Incentive Program Partner