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 > On Nov 19, 2020, at 8:19 AM, Ken Schaal <[email protected]> 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 <[email protected] > <mailto:[email protected]>> 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 <http://www.frenergy.net/> > 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 <http://www.taitem.com/> > >
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