The un-controlled conductor could be up to 15 feet, 10 on the roof and 5
in the building?
Mark Frye
Berkeley Solar Electric Systems
On 1/15/2014 2:02 PM, Daniel Young wrote:
Here is a link for a video where Mike Holt helps with an explanation
to your question.
https://www.youtube.com/watch?v=sUXShMZJorQ
Essentially, the rapid shutdown needs to keep the energized length of
conductors to within 10' of the array if on the roof (this rule is
only for arrays on buildings) or within 5' of building penetration. I
would assume that if you are 9' on the roof, you then only have 1' in
the building before you need the shutdown device.
So micro inverters and some DC-DC optimizers should comply with the
standard as is (since they prevent wires from being energized with _DC
voltage_ before they even leave the array). But string inverter
systems will need to get creative with how they address this. Midnite
solar disco combiners with the birdhouse seem to be a possible
solution, but they add a lot of cost to some smaller systems that
didn't even need combiners before, let alone disconnect combiners with
power supply cards and separate control boxes...
Hopefully a better solution for small string inverters is on the horizon.
With Regards,
Daniel Young,
NABCEP Certified PV Installation Professional^TM : Cert #031508-90
NABCEP Certified Solar Heating Installer^TM : Cert #SH031409-13
*From:*re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of
*Jeffrey Quackenbush
*Sent:* Tuesday, January 07, 2014 10:46 AM
*To:* 'RE-wrenches'
*Subject:* [RE-wrenches] NEC 2014 690.12 Rapid Shutdown
I've been going through the new Code book (which is in effect now in
Massachusetts) and found myself somewhat puzzled by the intent of the
new "rapid shutdown" requirement in 690.12. Does anyone have insight
into how this is supposed to be interpreted and implemented? I've put
together a list of my own questions, given below (the numbers
reference the new 690.12 text). Thanks!
*690.12 Rapid Shutdown*
1. Where should the rapid shutdown switch be located? (1) only says
that the shutdown function should be installed if the circuit is
longer than 10' or goes more than 5' into a building. If this
condition is fulfilled, it says nothing about where the switch should
be located. (2) says that controlled conductors should be limited to
30V, 240W, which will only be the case downline from the switch, so
this may mean that it should be located close to the source, i.e. on
the roof. But this is just an inference, and one that doesn't have
clear boundaries; every source conductor for a series connected PV
circuit (that is not Solar Edge, Enphase , etc.) will have a higher
voltage and wattage potential when the sun is shining /somewhere/
along its length, even if the disconnect is located very close to the
array. Or does this requirement mean that all systems will need to
have some kind of "smart" junction box, module DC-DC converter or
module level AC inverter? Furthermore, individual modules often have
higher voltages & wattages these days and there is no way to impose
limits on their electrical characteristics in any field wired
configurations. A listed AC module that sees the module leads as
internal would be the only scenario that would be exempt.
2. (5) asks that equipment performing the shutdown should be listed
and identified. Does that mean listed and identified for the purpose
of this specific requirement? Or just listed and identified to limit
voltage and wattage in 10 seconds? Does a specific UL standard exist
for the function they have in mind? Does any equipment exist that has
such listing and identification yet?
3. Is the rapid shutdown intended to be automatic or manual? If
automatic, what are the parameters that would trigger the shutdown? If
manual, are there any accessibility requirements?
4. Rapid shutdown seems more like a disconnect requirement than a
circuit requirement. Why limit circuits to 30V, 240W, instead of just
requiring a shutdown? Why 10 seconds, when all the disconnecting
functions (i.e. manual disconnects, and internal AFCI, GFCI & UL 1740
disconnects) happen in less than a second? (It hardly seems like a
"rapid" shutdown). Why write this article into section II rather than
section III?
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