[RE-wrenches] Two NEC questions

Sun Oct 14 09:44:13 PDT 2012

August,

Who at SMA said that they won't be shipping AFCI inverters? I know they have
been manufacturing. I have two of the AFCI inverters in operation at my
office and they are very impressive. Three months of operation since startup
without a single nuisance trip and it trips every time I simulate a fault. I
would press SMA on delivery since I believe they are available. It may be
either an internal hold on the product or bad information.

Eaton has released their AFCI component but it is not a listed component so
it has to be incorporated into a listed product like a combiner box or
inverter. 

Although the AFCI technology will have some issues in implementation, I
believe that it is going to solve a lot of safety issues, particularly with
residential systems. We have been seeing more and more series arc fault
failures in the field, so the timing could not be better. Even if you are in
a region that does not enforce the 2011 NEC yet, I would recommend seriously
looking at products in this area.

One word of caution. I believe AFCI products incorporated into inverters
will be more successful in the short term than products that are independent
of the inverter. The reason for this is simple. When the product developer
has the defined noise signature of the inverter, they can build a product
that accounts for the that noise signature (transistor switching). Without
that key piece of data, there will be stand-alone AFCI products that have
problems with particular inverters and other components (dc-dc converters).
These interactions are difficult to predict without product by product
testing. 

Over the next few years, products like the one from Eaton will create lists
of inverters that they know work well with their products. Until you get
some good data on that issue, be careful.

Lastly, it is way cool to be able to walk up to a combiner box or plug
connector and open it under load and see the inverter trip on the detected
arc-fault. These products will become common retrofit items as modules,
connectors, combiner boxes, and inverters have connection defects that start
fires. Often, the only cost-effective way to fix these connection problems
is with detection since replacing PV arrays and other products may be far
more costly than installing an AFCI detector.

Bill.

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of August Goers
Sent: Sunday, October 14, 2012 9:11 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Two NEC questions

Hi David and Rebecca -

We're still in the 2008 code cycle here in California so AFCI hasn't become
an issue yet. I just listened to a webinar by SMA last week and I believe
that their AFCI Sunny Boys wont' be shipping for at least a couple of
months.

Rebecca, have you already installed this system? What type of inverter do
you want to use? NEC 90.4 (Enforcement) states this:

"This Code may require new products, constructions, or materials that may
not yet be available at the time the Code is adopted. In such event, the
authority having jurisdiction may permit the use of the products,
constructions, or materials that comply with the most recent previous
edition of this Code adopted by the jurisdiction."

So, you might be able to convince the AHJ to enforce the 2008 NEC which
doesn't require AFCI. Or, use microinverters or ACPV as David mentioned
below.

Good luck out there!

-August 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of David
Brearley
Sent: Saturday, October 13, 2012 9:02 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Two NEC questions

RE Question #2: 

Article 100 defines a service as:

Service. The conductors and equipment for delivering electric energy from
the serving utility to the wiring system of the premises served. (emphasis
added)

PV system wiring simply does not fit that definition. The PV system is not
part of the serving utility. And inverters are not service equipment. 

You need to refers them to this definition in Article 705.2 (added in NEC
2011):

Power Production Equipment. The generating source, and all distribution
equipment associated with it, that generates electricity from a source other
than a utility supplied service. (emphasis added)

FWIW: Mike Holt has written for SP about the Code requirements for
interconnecting PV systems, as well as some additional recommendations for
making supply side connections:

http://solarprofessional.com/article/?file=SP5_1_pg14_QA
<http://solarprofessional.com/article/?file=SP5_1_pg14_QA&search=> &search=

RE Question #1: I had a local inspector ask me about this in late-August &
there were relatively few listed products at that time:

*	SMA America has dc AFCI in their standard SunnyBoy US-series
inverters (SB 3000-US, SB 3800-US, SB 4000-US, SB 5000-US, SB 6000-US,
SB7000-US, SB 8000-US):
http://www.sma-america.com/en_US/news-information/current-news/news/news/148
7.html
*	Microinverter systems (Enphase, Enecsys, etc.) typically do not
operate above 80 Vdc and are therefore exempt from 690.11
*	AC module systems (powered by SolarBridge, Exeltech, etc.) typically
do not operate above 80 Vdc and are therefore exempt from 690.11
*	SolarBOS reportedly has a dc AFDI and GFI combiner box:
http://www.solarbos.com/news/solarbos-puts-out-the-fire-in-pv-systems
(However, I don't see this product on their website under their regular
lists of products.)
*	While module-level dc-to-dc converters-like those from SolarEdge and
Tigo Energy-presumably have the ability to provide dc AFCI capabilities,
last I checked it didn't look like any of them were formally listed to do
so.

I suspect that most manufacturers are trying to avoid spending additional
money on testing until the market requires this. 

Have any wrenches here actually had an inspector required dc AFCI? Also, is
the dc AFCI test standard actually finalized and adopted at this point or
are companies testing to a draft standard? 

David Brearley, Senior Technical Editor

SolarPro magazine 
NABCEP Certified PV Installer T
david.brearley at solarprofessional.com
Direct: 541.261.6545

On Oct 13, 2012, at 10:12 AM, Rebecca Lundberg wrote:

Dear fellow wrenches,

Does anyone have suggestions for the 'best' way to keep up with product
availability for meeting 690.11 on DC AFCI? I understand that when this code
section was written there was no available device, and know that at least
several companies are working on devices. How will I know (before the AHJ
knows :-) that residential-scale products are available for purchase, and at
what point would you say now should be required over every other option?

Second question: I have an inspector insisting that the solar PV system is
the same as a utility service, and is requiring all of the required service
code references to apply. Anybody have a concise reference that might
convince him otherwise? This same inspector has decided that the electrical
permit will have adders for each inverter as service equipment, and each
module as an electrical device. It would sure be nice if there was more
consistency...we're still in the early adopter phase here in Minnesota.

Thanks in advance for your input.

Keep Shining!
Rebecca Lundberg
NABCEP Certified Solar PV Installer R
Owner/CEO, Powerfully Green
Rebecca.Lundberg at PowerfullyGreen.com
763-438-1976

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