<div dir="ltr">Hi All,<div><br></div><div>I have a follow up to this discussion. What's the proper way to think through this regarding ground mounts? It seems to me that if the goal is to protect firefighters then running a conduit underground and coming up to outdoor wall mounted inverters is keeping in the spirit of things, but I'm not sure if the language of 690.12 supports this. Am I mistaken? Do you have any best practice advice for this scenario?</div>
<div><br></div><div>Best regards,</div><div>-N</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Jan 21, 2014 at 12:36 PM, Drake <span dir="ltr"><<a href="mailto:drake.chamberlin@redwoodalliance.org" target="_blank">drake.chamberlin@redwoodalliance.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<br>
Bill,<br>
<br>
It is good to see that energized conductors are going to be disconnected
near the arrays. I've been an advocate of disconnecting these conductors
by ground fault sensing equipment since ground fault detection was first
implemented in the code. If contactors are to be installed on roofs, it
likely won't be long before both ground faults and arc faults are
automatically cleared. <br>
<br>
When the requirement for AC arc fault branch circuit protection was first
put in the NEC, it was postdated to allow time for the electrical
industry to adapt. This new remote disconnecting requirement does not
provide any lead time. <br>
<br>
As the 2014 NEC is adopted in various jurisdictions, inspectors may feel
that it is necessary to disallow systems without the newly required
disconnect feature. This may result in serious problems for solar
companies and customers, as well as manufacturers. <br>
<br>
The protection of firefighters is essential. The implementation of
renewables is essential also. Insurance claims for weather related,
global warming-triggered climatic disasters are rising exponentially.
Extreme weather related events result in major loss of life and billions
of dollars in property damage. Atmospheric CO2 levels continue to climb
from the burning of fossil fuels. This is a crisis of global proportions.
<br>
<br>
My request for code writers is to please take into account the effect
that inserting new rules into the NEC may have on the stability of
renewable energy, and implement new requirements in a way that will allow
for a smooth interface.<br>
<br>
Thank you, <br>
<br>
Drake <br><br>
<a name="143b5dffb7433f19__MailAutoSig"></a>Drake Chamberlin<br>
<i>Athens Electric LLC<br>
OH License 44810<br>
CO License 3773<br>
NABCEP Certified Solar PV <br>
<a href="tel:740-448-7328" value="+17404487328" target="_blank">740-448-7328</a><br>
</i><a href="http://athens-electric.com/" target="_blank">http://athens-electric.com/<br>
<br>
<br>
</a>At 12:45 PM 1/16/2014, you wrote:<br>
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Jeffrey,<br>
<br>
Sounds like you need to get involved in the code making process since you
have so many good ideas on how to improve the language. I like
confrontational discussions as long as they lead to a better
understanding and constructive outcomes.<br>
<br>
About 30 people worked on this language, so it is definitely not perfect.
However, I don’t think it is quite as bad as you make it out to be. I
wanted to jump in since some of your conclusions were not correct.<br>
<br>
This is a circuit requirement, not a disconnecting means requirement,
since it has to do with shock hazard of PV circuits in and around a
building. This is for firefighter safety. 30V is the international
standard for touch safe in a wet location. 240VA is to set a limit on the
available power on a circuit. Contactor combiners, which would be part of
a compliant solution, have 24V control circuits. The other reasoning for
240VA is that internally, 72-Cell PV modules can be divided into segments
of this power level for the foreseeable future (more on that another
day).<br>
<br>
If the conductors stay outside, you have 10’ from the array to place your
shutdown device. On large central systems, this would likely be a
contactor combinermost manufacturers sell these. If the conductors are
going immediately into the building, as with residential and integrated
systems, a shutdown device would have to be within 5’ of entering the
building. If goes outside for a while, then inside the building, the
total length could be no more than 10’ and no more than 5’ inside the
buildingthis is not additive. Remember, all this is for firefighter
safety.<br>
<br>
As Brian Mehalic and others have pointed out, the language does not
specify where the shutdown initiating device is to be located. The lack
of detail is more for flexibility than it is to give an AHJ license to
make an installer do anything they want. <br>
<br>
With grid-tie only systems (no battery backup), it would be most
convenient and cost effective to have a system that initiates the
shutdown on loss of utility. In this way, a firefighter can do what they
normally do, shut down utility power to the building, and the rapid
shutdown would automatically initiate. This does not necessitate an
additional disconnecting means for a load-side PV connection. The main
breaker could be the initiating device. For a supply-side connection, the
NEC already requires that the PV disconnect switch be located adjacent to
the service disconnecting means (article 230).<br>
<br>
The biggest issue with string inverters (central inverters) is that there
is a need to shutdown the capacitor input side of the inverter since that
stays energized for 5 minutes or more. The 10 seconds was to provide a
means to rapidly discharge the capacitors rather than requiring a relay
or tripping device. Doing something other than a relay will require a
test laboratory to evaluate the functionguess what?we don’t have a
standard yet to evaluate those products. Sounds like you might want to
work on that committee.<br>
<br>
It is more complicated for battery backup systems. Midnite Solar’s
birdhouse products are the best I have seen so far to address this
concern. Since dc and ac circuits are not differentiated, battery backup
systems need to have a shutdown process that works independently of a
utility outage for obvious reasons, and it must shutdown both the dc
circuits and the backup ac circuits. A separate switch, like the
birdhouse, would be necessary that only controls these functions in an
emergency situation.<br>
<br>
Is the language not detailedpossibly. This was done to provide
flexibility rather than create problems. Fire departments have been
requiring rooftop disconnects for years in California. These disconnects
are nearly worthless from a shock prevention point of view since
capacitors in the inverter stay charged or there are multiple
disconnecting means feeding each other. We have been trying to hold the
fire community off of rooftop disconnect requirements so we could work on
a solution that actually does what they want it to do. There is a long
discussion on this in the appendix of my “Understanding the CalFire
Guidelines” document on the SolarABCs website.<br>
<br>
The 2014 NEC language was a compromise worked out with the solar industry
(yes string inverter companies as well) in response to the first version
of the proposal which was to require module-level shutdown. This is not
module-level shutdown, it is PV output circuit shutdown (combiner box
shutdown is another way to look at it). However, the 2017 NEC cycle is
this year and there was a lot of talk about requiring module-level
shutdown this time around. <br>
<br>
I hope this helps. I will be writing articles for IAEI journal and other
periodicals on this subject since it was a very far-reaching and
potentially confusing new requirement in the NEC. Thanks for your
interest and let’s keep the constructive dialogue going on the subject.
It is time to get involved in the NEC update process again.<br>
<br>
Bill Brooks.<br>
<br>
<b>From:</b> <a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">
mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of
</b>Jeffrey Quackenbush<br>
<b>Sent:</b> Thursday, January 16, 2014 1:09 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] NEC 2014 690.12 Rapid Shutdown<br>
<br>
Wrenches,<br>
<br>
There is no guidance in the Code text for where the shutdown should take
place. (1) says: "Requirements for controlled conductors shall apply
only to PV system conductors of more than 1.5m (5') in length inside a
building, or more than 3m (10') from a PV array."<br><br>
<br>
So, the provisions <i>apply if</i> the circuit 10' from the array and 5'
inside a building, but no mention is made of where the shutdown actually
needs take place in the circuit. In the video Bill Brooks suggests that
the shutdown mechanism should also be placed within this 10'/5' boundary
but that is just an inference -- nowhere in the text is this actually
specified. If that was the intent of the Code committee, then they've
done a poor job actually expressing it in English.<br>
<br>
I'm concerned that some AHJs will interpret this to exclude all central
inverter systems (without the addition of cost-inducing secondary DC-DC
converters like Tigo) because the combiner or junction box can be many
feet from the actual beginning of a home run under the array.
Alternately, permissive AHJs could allow this function to be fulfilled
anywhere, meaning that the implementation won't meet the intent of the
writers.<br>
<br>
I'm also concerned, as Isaac mentioned, that there are no requirements
for how the shutdown be initiated, or that it contains of the
accessibility and grouping requirements that are always included for
disconnects. I really think this should be treated and categorized as a
disconnect requirement, not a circuit requirement, because that is the
ultimate function that's intended. <br>
<br>
I'm surprised none of the inverter manufacturers have chosen to comment
here, as this could dramatically impact the sales of central
inverters.<br>
<br>
Jeffrey Quackenbush<br>
<br><br>
<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">Nathan Charles<div>Engineer<br><div>NABCEP Certified PV Installation Professional #042013-20</div></div><div>Paradise Energy Solutions</div>
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