[RE-wrenches] Rooftop DC disconnects

[Ray Walters]

The other option is Midnite Solar's remote controlled breakers or=20
combiner boxes.  They make up to a 250 amp breaker, but I found on large=20
battery systems that we need some thing larger. Colorado is now=20
requiring Rapid Disconnect for the batteries as well, which is NOT the=20
original intent of that article.  Is the Gigavac UL listed?

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

On 9/24/2015 10:45 AM, Starlight Solar Power Systems wrote:
> William and Wrenches,
>
> I have pondered situations like this one and wonder the following: If=20
> a high voltage DC solenoid were placed at the PV array and the coil=20
> was controlled by an arc fault detector along with a means of manually=20
> disconnecting, would that not work to satisfy shut down requirements=20
> and safety concerns?
>
> We have been using 350A, 800 volt solenoids from Gigavac in our=20
> lithium battery system on both the positive and negative terminals=20
> (controlled by a CPU) to provide 100% disconnect if case of any=20
> battery fault.
>
> Larry
>
>
>
> On Sep 23, 2015, at 2:26 PM, William Miller <william at millersolar.com=20
> <mailto:william at millersolar.com>> wrote:
>
> Dear Fellow Wrenches
>
> Below is a design conundrum that may resonate with some of you:
>
> We are finalizing a design for an off-grid residential system.  The=20
> customer insist the PV should be on the roof and pre-installed a=20
> 1-1/4=E2=80=9D PVC conduit from his roof to a crawl space, in anticipatio=
n of=20
> a solar install.  This created real problems, because we all know we=20
> can=E2=80=99t pull PV source or output circuits in (or now, on)  the enve=
lopes=20
> of habitable buildings.
>
> There was no practical way to replace the PVC.  We contrived a method=20
> to sleeve =C2=BE=E2=80=9D liquid-tight through the 1-1/4=E2=80=9D PVC to =
the crawl space,=20
> continuing on with EMT.  This is the largest metallic conduit we could=20
> fit.  The distance was greater than 10 feet so we couldn=E2=80=99t use EM=
T. =20
> Due to the conduit size restriction, we upgraded to Morningstar 600=20
> volt charge controllers, allowing us to reduce conductor size.
>
> (As a sidebar, although the Morningstar is listed as a 600 volt charge=20
> controller, we have found no circumstance were we could take advantage=20
> of that high a voltage.  With the currently available high wattage=20
> modules, by the time we added enough in series to get to 600 volts, we=20
> were well beyond the wattage capabilities of the controller. For sake=20
> of design considerations, I suggest one regard these units as ~300=20
> volt charge controllers.)
>
> We now have plans for 300 volt PV feeders running down an interior=20
> wall and under the house, with no roof-top disconnecting means.  It is=20
> my understanding none are required.  I am not comfortable with this. =20
> In this scenario, there is no safe way to replace either of the two=20
> Morningstar controllers. Should someone drill through or damage the=20
> EMT in the wall or under the floor, there would be no way to turn off=20
> the feeder.
>
> I don=E2=80=99t like putting HU361RBs on a roof. They must remain vertica=
l and=20
> so they stick up too high and are hard to provide mounting for.=20
> Sola-deck units are another option, but they require integrating with=20
> shingles, not practical on this job or many others.  I finally settled=20
> on a DC-Sunvolt PV-X16A-4X-RG disconnect as a possible solution.  At=20
> $216 it is not out of range.  The unit will provide means to turn off=20
> the feeders for service.  I will report back on my impressions of the=20
> unit.
>
> To distill this scenario, I don=E2=80=99t believe the code requires a=20
> disconnect, but I feel morally obligated to install one.  I=E2=80=99d be =

> interested in verification of the code interpretation and others=20
> response to similar situations.
>
> I found no other options for rooftop disconnecting means that would be=20
> small, reasonably priced and not present a high profile.  If there are=20
> products I don=E2=80=99t know about, I would be most grateful to receive =
your=20
> input.
>
> While researching the hardware I stumbled upon this article, linked=20
> below.  It seems to present a real dilemma, but I am not convinced.=20
> Please remain skeptical as you read.  It appears all of the links=20
> direct you to the same source.
>
> https://www.linkedin.com/pulse/greatest-debacle-solar-pv-australias-rooft=
op-dc-isolator-lucas-sadler
>
> Thanks again to all of you for helpful advice and expertise.  I=20
> learned about Sunvolt here, just one of many great suggestions.
>
> Sincerely,
>
> William Miller
>
>
> <image002.jpg>
> Lic 773985
> millersolar.com <http://www.millersolar.com/>
> 805-438-5600
>
>
>
>
>
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