[RE-wrenches] GEC for Micro-Inverters and ACPV Modules

Tue Jan 15 11:29:25 PST 2013

August:

Yes, the entire GEC requirement is a pain in the neck and IMHO makes no sense for grid tied PV.
Historically it comes out of the rural electrification days when you had DC systems actually "supplying premises wiring", i.e. lighting circuits, outlets, etc.
In that context the bond between the DC circuit conductors and Ground is a critical conductor just as it is in an AC system supplying premises wiring.
If you lose the ground reference in one of these systems then the voltage on the circuit conductors can float all over the place and bad things can happen. (think loose neutral in a split phase AC system).
The Code requirements for a GEC are restrictive precisely to assure the integrity of the bond to ground.
I have long contended that grid tied PV systems do not supply premises wiring  and so the GEC requirement does not even apply.
Others in high places disagree.

No matter... the industry moving to ungrounded systems which eliminate the need in another way.
This is but one of many reasons I like ungrounded arrays.

Best Regards,

John Berdner
General Manager, North America

SolarEdge Technologies, Inc.
3347 Gateway Boulevard, Fremont CA 94538 USA  (*Please note of our new address.)
T: 510.498.3201 ext 747
M: 530.277.4894

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of August Goers
Sent: Tuesday, January 15, 2013 11:12 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] GEC for Micro-Inverters and ACPV Modules

Hi John,

I definitely see your point and that is why I was somewhat questioning the use of WEEBs with Enphase below. Enphases's instructions (link posted in thread below) seem to indicate a support of running the continuous GEC on the rack and then bonding the microinverter to the rack with WEEBs. Maybe I am misinterpreting the document or perhaps Enphase has another take.
There is no question that according to NEC 250.64(C) the GEC must be continuous. In the 2008 NEC handbook section 690.42 Point of System Grounding Connection has an application note "Connections are to be made in accordance with markings on the equipment or in the installation instructions."

All that said, it seems like technology is leaning towards listed AC Modules or floating array inverters. It sounds like that removes the requirement for a GEC which is great to help reduce installation costs.
The GEC has always been a pain in the neck.

Best,

August

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of John Berdner
Sent: Monday, January 14, 2013 7:07 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] GEC for Micro-Inverters and ACPV Modules

August:

The WEEB or other Listed grounding means between the inverter case and the structure are not "contiguous or irreversible spliced" and therefore do not meet the requirements for a GEC.
If the structure is then grounded via a bolt on lug it also is not irreversible or contiguous.
If you can unbolt something and disconnect the ground then it is not contiguous or irreversibly spliced.
Both of the above are ok for EGC but not for GEC.

GEC is a pain in the neck but the Code requirements are clear.
If the PV array conductor (pos or neg) is bonded to ground by the inverter then the inverter requires a GEC with all the related requirements - no if and's or but's.

Best Regards,

John Berdner
General Manager, North America

SolarEdge Technologies, Inc.
3347 Gateway Boulevard, Fremont CA 94538 USA  (*Please note of our new
address.)
T: 510.498.3201 ext 747
M: 530.277.4894

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of August Goers
Sent: Monday, January 14, 2013 4:32 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] GEC for Micro-Inverters and ACPV Modules

Hi Mark,

There have been some recent threads on this list touching on this topic.

As far as I understand, Enphase microinvertes still require a GEC up to and including the 2011 NEC. I don't know about the 2014 NEC. Enphase bonds the positive DC module conductor to ground. Pages 16 and 17 of their M215 installation manual address grounding:

http://enphase.com/wp-uploads/enphase.com/2011/06/Enphase_M215_Installatio
nOperation_Manual.pdf

Products such as Solar Bridge that are listed as Alternating Current (AC) Modules (per NEC 690.2) don't need a Grounding Electrode Conductor (GEC) as long as there are no conductors connected to ground within the product.
Solar Bridge has a good article on this:

http://solarbridgetech.com/microinverters-and-ac-pv-modules-are-different/

This all takes us back to using Enphase with grounding washers like WEEBs for the GEC. According to what I read in their instructions (and after many phone calls), it sounds like they are okay with us running the GEC on the racking in #6 and then bonding the microinverters to the rack with WEEBs. Seems a little strange but it's been working for us.

Good topic!

Best,

August
415.559.1525

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Mark Frye
Sent: Monday, January 14, 2013 3:31 PM
To: RE-wrenches
Subject: [RE-wrenches] GEC for Micro-Inverters and ACPV Modules

Does anyone have the latest on the GEC for micro-inverters/ACPV issue?

I know it is still in NEC 2008 and I believe 2011 with plans to address it in 2014.

I am specifically interested in the issue of GEC means continues (irreversible splices) and the whole business of the DC side of these devices constituting a separately derived system.

Enphase technical support is fine if the micro inverter chasis is bonded to a EGC only, but they leave the lug on the chasis if you want/need to build a GEC.

SolarBridge (pre-assembled micro-inverter) seems to be devoid of a chasis lug and therefore by extension does not/can not had a GEC in the system.

Exeltech (integrated micro-inverter aka. ACPV) does not seem to have a lug on its chasis.

Has the industry pretty much moved to not requiring a GEC for these devices and if so, how are the AHJ taking it?

Thanks,
Mark Frye
Berkeley Solar Electric Systems
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