HI Jason, My experience with fuses is that like breakers when you run them at or near their max rating they get hot and are prone to failure.
The added heat from environmental issues might be just enough to push it to failure. Given the good performance data from enphase you might be able to correlate production watts and ambient temperatures to find a pattern. Jay PS I haven’t researched enough to see if there are fuses rated for high heat and constant duty but that might be the answer if there are. > On Nov 19, 2020, at 3:25 PM, Jason Szumlanski > <ja...@floridasolardesigngroup.com> wrote: > > Very interesting, Jay. The Bussman curve I just looked up is very similar. > > If that is the sole issue then replacing the disconnect alone with an HD > version may not solve the problem. The better corrective action may be > increasing the fuse rating and the wire size accordingly. However, since this > is a 60A disconnect fused at 60A, that would require going to a 100A > disconnect. I suppose increasing one wire size to #4 and using 80A fuses in a > 100A disconnect may do the trick. > > Now I'm conflicted. I don't know for certain whether direct sunlight is the > primary issue since this happens on west walls under 18-inch eaves around > 1:30pm (an hour after solar noon). My issue could still be a faulty or poorly > designed switch. > > > > > > > On Thu, Nov 19, 2020 at 1:51 PM jay <jay.pe...@gmail.com > <mailto:jay.pe...@gmail.com>> wrote: > I looked up on the eaton site and found this information. Page 6, its a > temperature derate curve, which I think is your problem. > > In short, at 160F, for a slow blow fuse it is derated 20%. > At 176f its 25% derated. > > I couldn’t find any fuses that have a high temp rating. > > jay > > https://m.littelfuse.com/~/media/electrical/application-notes/powr-gard-technical-application-guide.pdf > > <https://mailtrack.io/trace/link/474b2c27b2bb1ff895f6a23e345df0a69acb9530?url=https%3A%2F%2Fm.littelfuse.com%2F~%2Fmedia%2Felectrical%2Fapplication-notes%2Fpowr-gard-technical-application-guide.pdf&userId=1613865&signature=bac567fe7daf0198> > > > >> On Nov 19, 2020, at 8:19 AM, Ken Schaal <k...@commonwealthsolar.com >> <mailto:k...@commonwealthsolar.com>> wrote: >> >> From my experience with reflective roofs galvanized quickly ages becoming >> less reflective! White is best aluminum paint next. >> Ken Schaal >> CommonWealth Solar >> >> On Thu, Nov 19, 2020, 9:17 AM frenergy <frene...@psln.com >> <mailto:frene...@psln.com>> wrote: >> This is a very timely discussion for us also as we have many >> Midnight MNPV6 discos in the sun. Though we're careful about tightening >> wire landings, using contact cleaner for the fuses and fuse holders, some >> installs seem to get hotter than others. We just started making a very >> simple sheet metal heat shield of sorts spaced away from the face of the >> disco for ventilation which keeps direct sun off the "face" of the disco. >> We don't paint this shield to give the galvanized surface a chance to >> reflect the IR. >> >> Its a retro which we've covered the cost for to prevent >> callbacks for blown (cooked?) fuses. I haven't done any before and after >> temp checks but I know from a long history of this kind of work that temps >> inside that disco will be substantially lower. They haven't been out in the >> field long enough to get any data. >> >> Bill >> >> Feather River Solar Electric >> Bill Battagin, Owner >> 4291 Nelson St. >> Taylorsville, CA 95983 >> 530.284.7849 >> CA Lic 874049 >> www.frenergy.net >> <https://mailtrack.io/trace/link/e207b30e79845ec63e96c341dfd15a38448beed2?url=http%3A%2F%2Fwww.frenergy.net%2F&userId=1613865&signature=67774b57601f832c> >> On 11/18/2020 5:13 PM, Ray wrote: >>> What is the brand and model of the disconnect? Temp ratings of the >>> terminals? I've definitely had fuse holders not make good contact with the >>> fuses and burn the fuses at one end, instead of in the middle. Have you >>> looked at it with a Thermal imaging camera when its operating to see if its >>> hot on one end of the fuse? >>> >>> Second, depending on the temperature it would be hitting inside the >>> enclosure in the sun, you could be exceeding the rating of the #6 >>> conductor. Assuming terminals rated at 75C, then from 310.16, a #6 is >>> rated 65 A, but derate for temperature of 114F inside the enclosure gets >>> you to .82 x 65 = 53.3, which is a bit less than the 54.45 that Dave just >>> calculated for continuous duty. >>> >>> What color is the disconnect painted? any chance of painting it white? >>> >>> Ray Walters >>> Remote Solar >>> 303 505-8760 >>> On 11/18/20 4:16 PM, Dave Tedeyan wrote: >>>> Jason, >>>> Bright sunny days, disconnect on the west side of house, maybe in the sun? >>>> 43.56A * 1.25 for continuous duty = 54.45A. If these disconnects are also >>>> baking in the sun, maybe the extra ambient heat is enough to push it over >>>> the edge? Just a thought. >>>> Cheers, >>>> Dave >>>> >>>> Dave Tedeyan, PE >>>> Senior Engineer | Taitem Engineering, PC >>>> >>>> 110 South Albany Street | Ithaca, NY 14850 >>>> o. 607.277.1118 x121 f. 607.277.2119 >>>> www.taitem.com >>>> <https://mailtrack.io/trace/link/efd4b878e42ee16e2448972912b6fb6479c555a5?url=http%3A%2F%2Fwww.taitem.com%2F&userId=1613865&signature=f6268c651176d2d9> >> >> > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > <mailto:RE-wrenches@lists.re-wrenches.org> > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > <https://mailtrack.io/trace/link/909d9292be62732c1591cf9d9797abfb06a5ca55?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=da0922ba13583903> > > There are two list archives for searching. 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