While I share Robin's optimism, I should also note the "NEC 2017 690.12
committee" referred to is not the code making panel. While it does have
(at least) one firefighter representative among a majority of PV
industry personnel, there's no guarantee that the Code Making Panel
approves this committee's proposal. There could very well be a competing
proposal from firefighters that requires cell-level shutdown every time
a red truck drives within 1/4 mile of an array, because "SAFETY!"
DKC
On 2014/8/28, 15:16, b...@midnitesolar.com wrote:
[Robin chiming in, below]
Dan, The 2014 690.12 is worded poorly. That is why there is so much
confusion. MidNite Solar is sitting on the NEC2017 690.12 committee.
There are a lot of smart people in this group. The 2017 version says
ALL PV SYSTEMS, not just on or in buildings. The 10 foot space gets
reduced to 1 foot like it always should have been.
There will be a lot of other clarifications too. The systems that use
shunt trip breakers [with Remote Trip coil] and contactors are for
string inverters. Shunt trip breakers will be used for battery based
systems and grid tie inverters with an AC outlet like the SMA TL
series. Micro inverters do not require anything like what our system
is. They can use the existing backfed breaker in the main distribution
box as long as it is labeled accordingly. Solar Edge has a system
that meets the Rapid Shutdown requirement also.
The UL standard for Rapid Shutdown has been written. It is going to go
out to a task force for review, comment and changes soon. MidNite
Solar will be on that task force. The MidNite Birdhouse is going
through UL now and is being evaluated to this new standard. All of our
disconnecting combiners and SOBs are already ETL listed. UL is
modifying the new Rapid Shutdown Draft standard as they come upon
things in the Birdhouse that the standard didn't consider. One of the
biggies that has not been sorted out is a requirement for feedback.
Contactors, power supplies and a switch will meet the requirement for
2014. The issue with this type of system is that when you push the
button to turn off the contactors, there is no way to tell that they
actually opened up. Without feedback that verifies that the contactors
are actually open, you are taking a chance with people's lives. 600VDC
contactors can weld themselves closed. If first responders don't trust
the Rapid Shutdown system, they are going to let the house burn. We do
have feedback on the birdhouse system. Contactors do not have
feedback. It is not simple to add this feature to a contactor based
system.
Installing a switch 15 feet up on the side of a building or on the
roof is not the intent of 690.12. This will not be allowed in 2017.
The exact placement of the initiating device (Birdhouse) is not cast
in concrete due to the differences in where main panel boards are
located, but it will not allow things like mentioned here 15 feet up
in the air or in the attic or on the roof.
Battery based systems are the most complicated to meet 690.12. The NEC
committee is deferring a lot of this to MidNite as we are already
doing it and have gone over all the different ways things can go
wrong. We started designing our system right after the Bakersfield
fire 5 years ago. The Bakersfield fire is what got the NEC to require
disconnecting combiners. We couldn't imagine why a fire fighter would
want to get up on the roof of a burning building to look for a
combiner? This is why we started the birdhouse project way before
anyone ever thought of the words Rapid Shutdown. Turns out this was a
good thing since battery backed up systems make the issue ten times
more complicated. We spent years working out issues and there were
lots of them that required a start from scratch approach numerous times.
AC coupling to a battery based inverter does not automatically meet
690.12 as someone mentioned in this thread. That battery based
inverter must also be shut off. The micro inverters would of course
shut off when the utility is shut down, but the battery based
inverters job is to keep things powered up when the grid is down. So
the battery based inverter has to be shut down also.
It would also make sense to shut off an auto start generator with the
Rapid Shutdown button. Some generators are designed to start up upon
loss of grid. Once the first responders have the meter pulled, that
could start up a generator and cause risk of shock. If the generator
is designed to start on low battery, it could start a day later when
the fire has been put out, but that also poses risk of electrical
shock when unexpectedly the part of the house that is left all of a
sudden comes live with juice.
The cost for a Rapid Shutdown system will vary a lot depending on what
you want to shut down. You do not need to run conduit to all the boxes
and switches. There is 600V Cat5e 90C USE-2 cable available that will
suffice. I don't see a system being installed for less than $1500 though.
Robin Gudgels
On 8/27/2014 8:45 AM, Dan Fink wrote:
Hi Mac, all;
Since Colorado just adopted NEC2014 July 1, I have not heard any AHJ
stories yet. But look at 690.12 (1):
"Requirements for controlled conductors shall apply only to PV system
conductors of more than 5 ft in length inside a building, OR more
than 10 ft from a PV array."
(my emphasis on "OR")
I interpret this to mean that if a ground mount array is more than 10
ft from the building, then any PV circuits that run up the outside of
the building from their trench (for example to penetrate the wall to
the power center on the inside) must be controlled because they are
"on" the building. And even if you penetrated right from the trench
into the crawl space, then up to the power center on the inside wall,
with less than 5 ft distance, still needs to be controlled if the
array is more than 10 feet from the building because of that "OR"
The logic and safety advantage of this for firefighters is another
topic entirely. As a first-arriving firefighter, I would spot the PV
racks on the ground, walk over to them, and throw the disconnects on
the nicely-labeled combiner boxes located within 10 feet of the array.
All thoughts appreciated, still puzzling this out.
Dan Fink
Buckville Energy
Otherpower
NABCEP / IREC / ISPQ accredited Continuing Education Providers
970.672.4342
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