Bill,
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.
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.
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.
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.
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.
Thank you,
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV
740-448-7328
<http://athens-electric.com/>http://athens-electric.com/
At 12:45 PM 1/16/2014, you wrote:
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_0F94_01CF129F.BCC65BD0"
Content-Language: en-us
Jeffrey,
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.
About 30 people worked on this language, so it
is definitely not perfect. However, I dont
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.
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).
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.
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.
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).
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 dont have
a standard yet to evaluate those products.
Sounds like you might want to work on that committee.
It is more complicated for battery backup
systems. Midnite Solars 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.
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.
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.
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 lets keep the
constructive dialogue going on the subject. It
is time to get involved in the NEC update process again.
Bill Brooks.
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org]
On Behalf Of Jeffrey Quackenbush
Sent: Thursday, January 16, 2014 1:09 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] NEC 2014 690.12 Rapid Shutdown
Wrenches,
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."
So, the provisions apply if 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.
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.
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.
I'm surprised none of the inverter manufacturers
have chosen to comment here, as this could
dramatically impact the sales of central inverters.
Jeffrey Quackenbush
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