[RE-wrenches] Rapid Shutdown

Tue Mar 15 13:57:48 PDT 2016

I thought this idea (attached) was a simple solution for array and battery rapid shutdown using a Classic controller and solenoids. The PV solenoids are 350 amp continuous @ 700 Vdc, and 400A @ 48 volts for the battery. Cost is about $120 each. 

Midnite told me than plan to implement the arc fault relay control. A simple SPST switch in series with the 12 volt Aux output will allow shutdown. Add a fire alarm output relay for auto-shutdown in case of fire. Seems like a simple, cost effective way to me.

Any comments Ray, Pete, Bill?

Larry Crutcher
Starlight Solar Power Systems

On Mar 15, 2016, at 12:48 PM, Patrick Shortell <pshortell6 at gmail.com> wrote:

Dear List,
Maybe it's an over simplistic opinion, but shouldnt all sources be disconnected rapidly in an emergency situation.
We can always do better than what the code requires. I get frustrated when people go to the book, (and try to hide behind the text).  instead of thinking through real life scenarios.
There are simple ways to work around these issues.
I find when something is questionable, Ill call the AHJ and get his approval First.
What would I do in my own house?
What if someone thought all the power was off when they dragged a hoseline into my basement.
My two cents
Pat

On Tue, Mar 15, 2016 at 1:10 PM, <billbrooks7 at sbcglobal.net <mailto:billbrooks7 at sbcglobal.net>> 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:re-wrenches-bounces at lists.re-wrenches.org <mailto:re-wrenches-bounces at lists.re-wrenches.org>] On
Behalf Of Ray Walters
Sent: Tuesday, March 15, 2016 9:02 AM
To: RE-wrenches <re-wrenches at lists.re-wrenches.org <mailto:re-wrenches at lists.re-wrenches.org>>
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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