[RE-wrenches] Enphase intermittent fuse trippjng

[jay]

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 <Ken at 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 <frenergy at psln.com <mailto:frenergy at 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 <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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