[RE-wrenches] Rapid Shutdown Battery Systems

Benn Kilburn benn at skyfireenergy.com
Thu Aug 27 10:03:50 PDT 2015


Ray,
Two quick suggestions...
1. Have you considered "leapfrogging" the battery connections? This would avoid the long negative cable run and have both positive and negative runs closer to the inverters. 
2. Could you locate the Birdhouse inside a lockable box or cabinet? 

Benn Kilburn
SkyFire Energy Inc. 
780-906-7807


> On Aug 27, 2015, at 9:29 AM, Ray Walters <ray at solarray.com> wrote:
> 
> Thanks for the Clarification Bill,  I may forward your comments to the AHJ at some point.  The system is proposed to be located in the 4 car garage, so there will be cars filled with gasoline in there as well.
> I always keep my battery cable runs short as possible, in this case the bank will be long and skinny, but the positives can be located at the end near the inverters.  The negative (grounded conductor) will have the long run through the battery enclosure.  Only the 3rd inverter would be more than 5 ft from the battery enclosure.  I am considering a battery combiner box with breakers for each string (only 2 strings) to meet 690.71(H)
> As others have pointed out, killing the AC output of the inverters is much easier to accomplish remotely.  Locking the Birdhouse would prevent unauthorized disconnection of critical loads, but unfortunately the Birdhouse does not have lockable cover, so that is still a very real concern for the owners.  As you pointed out, the real danger of the backup system is the batteries themselves, I spoke with firefighters this week, and they have to go into HAZMAT mode when they start dealing with a large battery bank. So as you mentioned, the short run of 48 vdc is not what they are concerned with.
> My main goal at this point is not to get red tagged and have to retrofit a bunch of expensive, special order gear later.  Our motto: "Do it right the first time" is easy to say, but can be hard to live up to.
> 
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer,
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
> 
>> On 8/26/2015 10:19 PM, billbrooks7 at sbcglobal.net wrote:
>> Ray,
>> 
>> Do you have a massive battery bank and 3, 8kW inverters inside the house? Is
>> this in a garage or power shed. If it is a power shed, then 690.12 is not
>> intended to relate to the power shed. That will be clarified in the 2017
>> NEC.
>> 
>> The area for discussion is what constitutes the length of battery cables.
>> 690.71 has restrictions on where overcurrent protection needs to be for
>> circuits longer than 5'. Do people really follow that religiously? This
>> would be a discussion that really needs to happen with the AHJ. My basic
>> view is that if I have a 4' run from a battery box to my inverters (even
>> though one lead may be 10' long), many would call that a 4' run. That is
>> what is exposed from a fire fighter point of view. Remember the battery is
>> potentially a massive bomb in a fire, so 48V conductors are the least of a
>> fire fighter's concern.
>> 
>> Bottom line is how to make it easy for a firefighter to kill the vast
>> majority of wires in a building. A backup system simply reenergizes
>> everything. Cutting off the dc from the array and the ac out of the
>> inverters solves the problem--keep the battery as close as possible and
>> don't worry about trying to turn off the battery circuit to the inverter.
>> 
>> Bill.
>> 
>> 
>> -----Original Message-----
>> From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
>> Behalf Of Ray Walters
>> Sent: Wednesday, August 26, 2015 12:40 PM
>> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>> Subject: [RE-wrenches] Rapid Shutdown Battery Systems
>> 
>> Hi Wrenches;
>> 
>> I have an upcoming project to be inspected, ,and having spent too much time
>> on off grid and out of country work, I'm now playing catch up with the new
>> 690.12 and 690.71(H) requirements.
>> The proposed GTB system is 3 Radians with a ground mounted 18kW array and
>> large HUP battery bank.  I just read a Bill Brooks article that basically
>> says that Rapid Shutdown not only applies to ground mounted arrays that come
>> into buildings, but also applies to battery cables if longer than 5 ft.
>> There are 690.12 compliant combiners from Midnite that work with their
>> Birdhouse system, so I think I've got a handle on the array requirements
>> (more or less).
>> What is stumping me is how to feed three 8kW inverters from a large battery,
>> and install auto disconnect breakers within 5 ft.
>> 1) the disconnect has to be large enough, Midnite only makes a 250 amp
>> remote trip breaker, so I'd have to parallel 3 of these?
>> 2) 690.71(H)3 says the breaker can't be in the battery enclosure, which is
>> tricky since the enclosure is 160" long from one end to the other with 2
>> parallel strings.
>> 3) I'm having trouble even finding an enclosure for 3 large DC breakers
>> (Flex 1000 is the only thing I know of) and to get the enclosure close
>> enough is an issue too.
>> I just got off the phone with Tech support at Outback and they don't seem to
>> have any Rapid Shutdown gear ready.
>> Are inspectors actually requiring this yet, or because of the lack of
>> available UL listed products, can we take a pass on at least some of the
>> requirements?  Another strategy the Outback tech thought of is to put all
>> the equipment into a shipping container and then its not in or on a
>> "building", and 690.12 doesn't apply.
>> 
>> --
>> R.Ray Walters
>> CTO, Solarray, Inc
>> Nabcep Certified PV Installer,
>> Licensed Master Electrician
>> Solar Design Engineer
>> 303 505-8760
>> 
>> _______________________________________________
>> List sponsored by Redwood Alliance
>> 
>> List Address: RE-wrenches at lists.re-wrenches.org
>> 
>> Change listserver email address & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>> 
>> List-Archive:
>> http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
>> 
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>> 
>> Check out or update participant bios:
>> www.members.re-wrenches.org
>> 
>> 
>> ---
>> This email has been checked for viruses by Avast antivirus software.
>> https://www.avast.com/antivirus
>> 
>> _______________________________________________
>> List sponsored by Redwood Alliance
>> 
>> List Address: RE-wrenches at lists.re-wrenches.org
>> 
>> Change listserver email address & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>> 
>> List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
>> 
>> List rules & etiquette:
>> www.re-wrenches.org/etiquette.htm
>> 
>> Check out or update participant bios:
>> www.members.re-wrenches.org
> 
> _______________________________________________
> List sponsored by Redwood Alliance
> 
> List Address: RE-wrenches at lists.re-wrenches.org
> 
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
> 
> List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
> 
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
> 
> Check out or update participant bios:
> www.members.re-wrenches.org
> 



More information about the RE-wrenches mailing list