"In this scenario, there is no safe way to replace either of the two Morningstar controllers."
The BEST rooftop disconnect remains... a big thick tarp. Not totally practical in an emergency situation, but it is pretty fail safe. Unfortunately for emergency responders, that does not take care of the AC circuits in a microinverter or AC module system, but ideally the building main is shut down anyway, and the risk is the same as any other 240V equipment/appliance circuits. Jason Szumlanski On Wed, Sep 23, 2015 at 4:26 PM, William Miller <will...@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 > > > > > > [image: Gradient Cap_mini] > Lic 773985 > millersolar.com <http://www.millersolar.com/> > 805-438-5600 > > >
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