Brian: I agree 100%. Handling a tarp on a roof is impractical, ineffective and unreliable. Wind and slope are just two factors that increase danger and reduce reliability.
William > On Sep 24, 2015, at 9:12 AM, Brian Mehalic <br...@solarenergy.org> wrote: > > I disagree about tarps. We've tested fully covered arrays (and small ones at > that) and still had what would be considered lethal levels of current and > voltage, even when using heavy, reflective tarps. And it can be very > difficult to ensure they stay in place, plus it's impractical for larger > arrays. > > Brian > >> On Sep 24, 2015, at 6:31 AM, Jason Szumlanski >> <ja...@floridasolardesigngroup.com> wrote: >> >> "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 >>> >>> >>> >>> >>> >>> >>> Lic 773985 >>> millersolar.com >>> 805-438-5600 >>> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> List Address: RE-wrenches@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@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 >
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