Usually it is repairing work of others who miscalculate the required rating. When it gets really cold (that means 0ºF here), we start to get calls with blown fuses. We do have our fair share of unexplained blown string fuses, and I attribute most of those issues to extreme heat in enclosures that are highly exposed to the sun.
Jason Szumlansk i On Wed, Apr 30, 2014 at 11:21 AM, Drake < drake.chamber...@redwoodalliance.org> wrote: > Inverter ground fault fuses certainly do blow. What is causing your > string fuses to go? > > > At 10:17 AM 4/30/2014, you wrote: > > "​ > > An AC breaker is far more likely to trip than a DC string fuse" > > I completely disagree. We have never, not once, had to reset a tripped > inverter output circuit AC breaker that I know of, but have replaced many > dozens of DC string fuses and GFCI fuses in inverters, most of the time for > undiagnosed failures.​ There is a reason we keep a good supply of 1A, > 15A, and 20A Littlefuses in a drawer here. > > Jason Szumlanski > > >  > > > On Wed, Apr 30, 2014 at 9:56 AM, Drake <drake.chamber...@redwoodalliance.org> > wrote: > There are good reasons to want to put AC combiners under modules, but > some reasons not to want to. > ​​ > An AC breaker is far more likely to trip than a DC string fuse, due to the > surge availability. As a PV system is designed to last a minimum of 25 > years, the installer might not be the one to sort out problems decades down > the line. > > A strategy I prefer would be to use a SolaDeck as a junction box. Run > small wires to a convenient AC combiner location. > > > At 12:43 PM 4/29/2014, you wrote: > > Dave > > I agree, in the case of microinverters, you already have a main PV System > disconnect at the Load Panel to shut down the system that is readily > accesible. I would consider the disconnect on the roof as a supplemental > disconnect for the purposes of maintenance by authorized personal that only > needs to be accessible. > > Bill > > > On Tue, Apr 29, 2014 at 8:44 AM, Dave Click <davecl...@fsec.ucf.edu > > wrote: > I think 240.24(A)(4) allows the installation of the inverter OCPDs in the > SolaDeck hidden under a module. > 240.24 Location in or on Premises. > (A) Accessibility. Overcurrent devices shall be readily accessible and > shall be installed so that the center of the grip of the operating handle > of the switch or circuit breaker, when in its highest position, is not more > than 2.0 m (6 ft 7 in.) above the floor or working platform, unless one of > the following applies: > ... > (4) For overcurrent devices adjacent to utilization equipment that they > supply, access shall be permitted to be by portable means. > > And if panelboards / fused safety switches are allowed to have > screwed-down covers over the OCPDs, I'd think that installing a removable > module over these OCPDs would meet NEC. I guess an AHJ could argue that > this requires TWO covers be removed, unlike a panelboard or a switch. > DKC > > On 2014/4/29, 11:15, Jason Szumlanski wrote: > > 690.9(D) is not applicable to the original discussion because we were > talking about an Inverter output circuit, not a PV Source or Output circuit. > 690.34 may apply if you call a SolaDeck with breakers a junction box, but > I can see that being a stretch in the mind of many. > My and Ray's question about the screws on the SolaDeck cover itself > requiring a tool to render it accessible is still an issue if the breakers > themselves need to be "readily accessible," but that would also apply to a > Midnite MNPV, which also has a cover with a screw. > > Jason Szumlanski > > On 4/28/2014 5:57 PM, Bill Brooks wrote: > > Read 690.9(D) and 690.34. Not sure where this “hysteriaÂrun for the > border†sentiment is coming from. > >  > 690.9(D) Photovoltaic Source and Output Circuits. Listed PV > overcurrent devices shall be required to provide overcurrent > protection in PV source and output circuits. The overcurrent > devices shall be accessible but shall not be required to > be readily accessible. >  > 690.34 Access to Boxes. Junction, pull, and outlet boxes > located behind modules or panels shall be so installed that > the wiring contained in them can be rendered accessible > directly or by displacement of a module(s) or panel(s) secured > by removable fasteners and connected by a flexible > wiring system. >  > This is not a change. Please help me understand the concern. >  > Bill Brooks. >  >  > From: re-wrenches-boun...@lists.re-wrenches.org [ > <re-wrenches-boun...@lists.re-wrenches.org> > mailto:re-wrenches-boun...@lists.re-wrenches.org<re-wrenches-boun...@lists.re-wrenches.org>] > On Behalf Of Ray Walters > Sent: Monday, April 28, 2014 2:23 PM > To: RE-wrenches > Subject: Re: [RE-wrenches] (no subject) >  > Interesting so does "require a tool" include taking a screw off the cover > plate of the combiner box, too? > What a game changer. I'm going to Mexico for my next project; I'll > actually enjoy even more being the sole AHJ on the project. > > > > R.Ray > Walters > > > > CTO, Solarray, > Inc > > > > Nabcep Certified PV Installer, > > > > Licensed Master > Electrician > > > > Solar Design > Engineer > > > > 303 > 505-8760 <303%20505-8760> > > On 4/28/2014 2:52 PM, Michael Morningstar wrote: > > Readily accessible is now defined in the 2014 NEC. Installing OCPD’s > underneath a module is a major faux paux, and I can’t imagine any AHJ > thinking otherwise. Having to remove a module in order to reset a breaker, > what a drag. >  > "Capable of being reached quickly for operation, renewal or inspection > without requiring those concerned to use a tool, to climb over, remove > obstacle or other.†>  > Michael >  >  >  > > > On Apr 28, 2014, at 10:29 AM, William Miller <will...@millersolar.com > > wrote: > > > > You call it a solar panel, I call it a glass j-box cover plate. > William > Miller Solar > > > On Apr 28, 2014, at 9:21 AM, Jason Szumlanski <ja...@fafcosolar.com> > wrote: > If that is the interpretation, I don't see how the breakers are "readily > accessible" in a SolaDeck mounted anywhere, regardless of whether it is > under a module. It requires removal of four screws (using a tool) to > access the breakers inside the enclosure. It's all up to the AHJ. It has > not been an issue locally here. 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