Hi Bill;
First, I didn't intend to "shoot the messenger". I have appreciated
your many contributions to the PV industry, and enjoyed your education
courses over the years. Thank You.
However, 'PV system circuit' is not 'self defined' as you stated. By
that same interpretation, a single GT system could then cause an entire
city to fall under the requirements of rapid disconnect, because a
portion of everyone's power would be coming from PV. Obviously, we have
to draw a line somewhere sensible just where the photovoltaic circuit
stops and the other circuits start. A modern off grid power system
actually consists of numerous circuits each subject to its own rules,
wire and breaker sizing, etc.
A reasonable interpretation is thus: if you remove the PV from the
system, the remaining components are not part of the 'PV system
circuit'. We can all agree that an inverter generator system with out
PV is not subject to 690, but 705. Adding a single PV module should not
suddenly change the requirements for every other circuit in the house.
Disconnect the PV module in compliance with 690.12, and the rest of the
system should no longer be considered part of the PV Circuit.
690.12 should accomplish the same result as previous, slower methods to
deenergize a PV array (blanket over the array, or wait till the sun goes
down) Our design does the same in an instant: push the Birdhouse button
and all Photovoltaic power beyond the array is off, just like we turned
the sun itself off.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 3/15/2016 11:10 AM, [email protected] wrote:
Ray,
I guess I have to step in after that acknowledgement. PV system circuit is a
self-defined term and therefore cannot be defined unless you are going to
develop a meaning that is different from the self-definition. It means ANY
circuit in a PV system. This includes battery and stand-alone circuits in
the 2014 NEC.
The language of the 2014 NEC was a compromise between the fire service and
the PV industry. Originally, the language required essentially module-level
shutdown. I raised the concern with the PV industry to get them involved
since most were not paying attention at the time. This language was
developed and intended to cover all circuits in a PV system. In the 2014
NEC, batteries are part of a PV system and therefore fall under this
requirement.
In the 2017 NEC, we were very careful to carve out all batteries and loads,
that were previously part of PV systems, and place them in their own
articles. Don't shoot the messenger on this one and don't think for a minute
that I alone made this requirement or am alone in interpreting it in this
way. I did author this compromise with other representatives of the PV
industry so I think I know what the intent was.
It is understandably difficult for battery systems and I would try to keep
battery circuits as short as possible. The 5-feet was intended to match the
requirement of 690.71(H)--which is further evidence of the intent of the
2014 NEC.
The 2017 NEC removes batteries from the requirement, but they still cannot
backfeed the PV array. Energy storage systems (Article 706) will have their
own requirements in time--that is guaranteed.
Bill.
-----Original Message-----
From: RE-wrenches [mailto:[email protected]] On
Behalf Of Ray Walters
Sent: Tuesday, March 15, 2016 9:02 AM
To: RE-wrenches <[email protected]>
Subject: [RE-wrenches] Rapid Shutdown
Greetings Esteemed Wrenches:
I've just heard back from our inspector here in Colorado, and we are still
being required to disconnect the batteries under 690.12. No where in 690.12
are batteries mentioned, nor in the appropriate 690.71 section that deals
with batteries. The entire reasoning behind this is based on a single
article written by a single person: Bill Brooks. I have contacted both
Outback and Magnum on this issue, and their engineers are unaware that rapid
shutdown applies.
My interpretation is that I could install an inverter and battery system
that was charged from a generator, and we would not need any rapid shutdown
at all. But according to Bill, as soon as I put a single solar module into
the system, suddenly the entire system becomes PV? The problem lies with the
term 'PV System circuit' used in 690.12. 690.2 Defines 'PV Output
circuit', and 'PV source circuit', but there is no 'PV system circuit'
defined. 690.12 therefore uses an undefined term.
Our design uses 2 inverters, so if we used Midnite's E panel with their
remote trip breakers, the 2nd inverter would be more than 5 ft from the
batteries. If we used Magnum or Outback DC disconnects (that would comply
with the 5 ft rule specified in 690.71) they don't offer remote trip.
We have a Midnite Rapid disconnect Combiner on the roof with the Birdhouse,
so we are complying with 690.12, it should not be applied to batteries
though.
Thanks,
--
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
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