[RE-wrenches] Rapid Shutdown Battery Systems

Wed Aug 26 16:26:43 PDT 2015

I spoke with Phil Undercuffler from Outback, who is a long term 
respected member of our list (and nice guy).  He basically said there is 
a lot of misinformation on 690.12, but essentially it should only be 
applied to roof mounted PV, and that it is specifically to address 
firefighters' need to quickly vent the roof in the event of a fire. This 
original intent has nothing to do with ground mounted PV, batteries, 
backup inverter power, etc.  Bill's more encompassing interpretation 
holds solar installers to a much higher standard than other electrical 
installations.  UPS and backup generator systems for instance, that do 
not include PV, do not have to worry about Rapid Shutdown.
690.71 requiring a disconnect near the batteries, is still applicable, 
but it is really unclear how exactly the 5 ft should be measured.  The 
battery combiner box from Midnite is what I was looking for, Thanks 
Tump.  I plan to have breakers on the 2 separate parallel battery 
strings, so I think I will be able to make the 5 ft rule.  Before, the 
furthest inverter disconnect was definitely going to be beyond 5 ft from 
the battery.  I am still considering including the battery disconnects 
in the Rapid Shutdown system, but as Phil pointed out: this defeats the 
purpose of having a backup system, if anyone can just walk up to the 
outside of the house, push a button, and shut down all your critical loads.
Once again, its all going to come down to the AHJ's view, though I will 
do my part to put him in touch with folks like Phil, who as the 
manufacturer's rep of the UL listed product has some say on how their 
equipment is to be installed.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 8/26/2015 4:44 PM, Tump wrote:
> I know that IF the SMA SI  master inverter is shut down then all 
> follow, shunt trip breaker only for the master? Also look at the 
> Midnite MNBCB 1000/50 
> <http://www.midnitesolar.com/productPhoto.php?product_ID=439&productCatName=Battery%20Accessories&productCat_ID=39&sortOrder=4&act=p> 
>
> (Previous Model Num: MNBCB-1000/50-Battery Combiner)
> MidNite 1000amp battery combiner box
> Includes a 1000amp Positive and Negative bus bar with 3/8 inch studs.
> On Aug 26, 2015, at 3:39 PM, Ray Walters wrote:
>
>> 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
>>
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