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
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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