[RE-wrenches] Rooftop DC disconnects

Sat Sep 26 08:20:45 PDT 2015

Larry,
Could you possibly sketch out a rough schematic for what you are talking
about here? It would help me understand your suggestion better.
Thanks, Howie

Howie Michaelson
NABCEP Certified Solar PV Installer™

Catamount Solar
Renewable Energy Systems Sales and Service
VT Solar Electric Incentive Partner
http://www.CatamountSolar.com
802-272-0004
On Sep 25, 2015 12:18 PM, "Starlight Solar Power Systems" <
larry at starlightsolar.com> wrote:

> Hi Gary,
>
> That is exactly what I am considering. Because of the inconvenience of
> reset and lack of automatic shutdown, I suggest the use of solenoids with
> the Classic Aux control so the system will shut down the instant arc fault
> is detected. It is easily reset from the battery location or anywhere you
> wire the reset circuit. By supplying the coil voltage until the controller
> takes over, the entire power system will restart; no trip to the roof. I
> built a reset control using a simple wireless relay with a key fob remote
> to perform the reset. Cost about $20.
>
> The Birdhouse requires human action, my idea does not but can be still be
> activated by a person. Of course the Birdhouse offers many other shutdown
> features for grid tie. But for a typical off grid installation, shutting
> down the PV array and battery means all power is off at the source. If
> there is a reason this will not work, I would like to know it. For a couple
> hundred dollars, it seems like a cost effective and desirable approach.
>
> Larry
>
>
> On Sep 24, 2015, at 8:51 PM, Gary Willett <Gary at IcarusSolarServices.com>
> wrote:
>
> Larry:
>
> The MidNite Solar 250A breakers used for battery bank disconnect, and the
> breakers in the "Bird House" controlled roof-top mounted disconnecting
> combiners, use a "shunt-trip" mechanism inside the circuit breaker. This
> requires a manual reset to restore the disconnected circuits. This can be
> inconvenient if the enclosure housing the shunt-trip breaker is not easily
> accessible (i.e. on a two story house with a 6:12 roof pitch.  Something to
> consider.
>
> Regards,
>
> Gary Willett PE
> Icarus Engineering
>
>
> On 9/24/15 7:26 PM, Starlight Solar Power Systems wrote:
>
> William, Ray,
>
> I asked Midnite about using the Aux circuit for control for ground or arc
> faults. They said this will (should) be added on the next firmware update.
> This means if an arc fault is detected, the Classic will shut down AND
> conductors leaving the array would be de-energized by switching off the HV
> relay. All automatically. A second relay could be connected to the battery
> for total system shutdown. Should be easy to build a circuit to re-energize
> everything after a fault.
>
> Wouldn't this automatic method be better than waiting for someone to throw
> a switch to shut things down? You would have to run the low voltage control
> wire and perhaps put the relays in an enclosure. A disconnect switch could
> be in series for manual shutdown. What am I missing?
>
> Larry
>
>
>
> On Sep 24, 2015, at 11:03 AM, Ray Walters < <ray at solarray.com>
> ray at solarray.com> wrote:
>
> The other option is Midnite Solar's remote controlled breakers or combiner
> boxes.  They make up to a 250 amp breaker, but I found on large battery
> systems that we need some thing larger. Colorado is now requiring Rapid
> Disconnect for the batteries as well, which is NOT the 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 Engineer303 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 a
> high voltage DC solenoid were placed at the PV array and the coil was
> controlled by an arc fault detector along with a means of manually
> disconnecting, would that not work to satisfy shut down requirements and
> safety concerns?
>
> We have been using 350A, 800 volt solenoids from Gigavac in our lithium
> battery system on both the positive and negative terminals (controlled by a
> CPU) to provide 100% disconnect if case of any battery fault.
>
> Larry
>
>
>
> On Sep 23, 2015, at 2:26 PM, William Miller <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
> customer insist the PV should be on the roof and pre-installed a 1-1/4” PVC
> conduit from his roof to a crawl space, in anticipation of a solar
> install.  This created real problems, because we all know we can’t pull PV
> source or output circuits in (or now, on)  the envelopes of habitable
> buildings.
>
> There was no practical way to replace the PVC.  We contrived a method to
> sleeve ¾” liquid-tight through the 1-1/4” PVC to the crawl space,
> continuing on with EMT.  This is the largest metallic conduit we could
> fit.  The distance was greater than 10 feet so we couldn’t use EMT.  Due to
> the conduit size restriction, we upgraded to Morningstar 600 volt charge
> controllers, allowing us to reduce conductor size.
>
> (As a sidebar, although the Morningstar is listed as a 600 volt charge
> controller, we have found no circumstance were we could take advantage of
> that high a voltage.  With the currently available high wattage modules, by
> the time we added enough in series to get to 600 volts, we were well beyond
> the wattage capabilities of the controller.  For sake of design
> considerations, I suggest one regard these units as ~300 volt charge
> controllers.)
>
> We now have plans for 300 volt PV feeders running down an interior wall
> and under the house, with no roof-top disconnecting means.  It is my
> understanding none are required.  I am not comfortable with this.  In this
> scenario, there is no safe way to replace either of the two Morningstar
> controllers. Should someone drill through or damage the EMT in the wall or
> under the floor, there would be no way to turn off the feeder.
>
> I don’t like putting HU361RBs on a roof.  They must remain vertical and so
> they stick up too high and are hard to provide mounting for.  Sola-deck
> units are another option, but they require integrating with shingles, not
> practical on this job or many others.  I finally settled on a DC-Sunvolt
> PV-X16A-4X-RG disconnect as a possible solution.  At $216 it is not out of
> range.  The unit will provide means to turn off the feeders for service.  I
> will report back on my impressions of the unit.
>
> To distill this scenario, I don’t believe the code requires a disconnect,
> but I feel morally obligated to install one.  I’d be interested in
> verification of the code interpretation and others response to similar
> situations.
>
> I found no other options for rooftop disconnecting means that would be
> small, reasonably priced and not present a high profile.  If there are
> products I don’t know about, I would be most grateful to receive your input.
>
> While researching the hardware I stumbled upon this article, linked
> below.  It seems to present a real dilemma, but I am not convinced.  Please
> remain skeptical as you read.  It appears all of the links direct you to
> the same source.
>
>
> https://www.linkedin.com/pulse/greatest-debacle-solar-pv-australias-rooftop-dc-isolator-lucas-sadler
>
> Thanks again to all of you for helpful advice and expertise.  I 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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