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Old 09-10-2016, 05:40 PM   #1
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Somewhat scary solar meltdown

...So I noticed that my house batteries weren't charging today......

I have 320W of solar on the roof wired in parallel, and run 10AWG wire from the panels to a Blue Sea fuse block (positive only) through a 25A fuse and on to the solar controller.

Here's what the fuse block looks like today:








......and here's the wire termination from the panels to the fuse block...




After an extensive post-meltdown forensic analysis (come on.....really??....), my conclusions are either:

I didn't tighten the fuse block terminal screw sufficiently and the contact resistance at the screw terminal created enough heat to melt the fuse block

or

The screw was sufficiently tight, but the thermal cycling of pumping 16A thru the terminal at high noon and cooling everything off at midnight slowly worked the screw loose.....increasing contact resistance at the screw enough to melt plastic.



...just happy my van didn't burst into flames.....
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Old 09-10-2016, 05:55 PM   #2
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You can make a lot of heat with 20 amps. It reminds me of my 30 amp 110 inlet plug meltdown. We were both lucky that there was no fire.
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Old 09-10-2016, 06:56 PM   #3
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No fuse between the controller and the distribution panel??

I'm a bit confused as to how a loose contact did this without some sort of short to ground. I'm not an electrical wiz though, but I got the basics. Seems like it had to arc to something right?? Almost looks like it arced to the top of that 25 amp blade fuse.

I was reading up on those blade fuses and they are not exactly quick acting. They can draw overcurrent for minutes at a time.

I am very glad your damage was minimal. Yikes!!

EDIT: I get it now, there was some current draw on the other side, loose connection turns into a resistance heater.

Yikes again.
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Old 09-10-2016, 07:06 PM   #4
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Greetings Boywonder, first, just want to say how I'm relieved something worse didn't happen. Second, that amount of amps is a lot to ask from a spade connector to handle. I would recommend a cable lug terminal for for anything north of 10 amps. If there is any consolation to this is you might have just found a point of high resistance that's been robing a chunk of your solar power.

-Eric
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Old 09-10-2016, 08:29 PM   #5
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Quote:
Originally Posted by ShuttlePilot View Post
Greetings Boywonder, first, just want to say how I'm relieved something worse didn't happen. Second, that amount of amps is a lot to ask from a spade connector to handle. I would recommend a cable lug terminal for for anything north of 10 amps. If there is any consolation to this is you might have just found a point of high resistance that's been robing a chunk of your solar power.

-Eric
ditto, also it looks like in effect your are terminating to the fuse on the fuse panel. This also increases heat in the area. Do you also have it fused at the controller?

-greg
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Old 09-10-2016, 09:59 PM   #6
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Yikes! Glad it wasn't worse!

I'm trying to remember how I did mine.. I think controller to battery is like 6 gauge through a big car stereo fuse, but I don't remember off the top of my head.
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Old 09-11-2016, 01:50 PM   #7
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ditto, also it looks like in effect your are terminating to the fuse on the fuse panel. This also increases heat in the area. Do you also have it fused at the controller?

-greg
....not sure what you mean by terminating to the fuse on the fuse panel....

The controller is about 2 feet away...this is the fuse from the panels....the fuse between the controller and house batteries is about 2 inches from the controller.....a different Blue Sea 6 circuit with ground buss.

.....thinking about using an in-line ATO fuse holder with butt-splices to eliminate the screw terminals.............
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Old 09-11-2016, 02:10 PM   #8
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Oh, so this is fuse between panels and controller.. I get it now, higher amps. I don't think I have a fuse... just straight from panels to controller, I think that's the way Blue Sky recommended. Is that bad?
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Old 09-11-2016, 02:28 PM   #9
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^ I'm wondering the same thing as I gather components for my upcoming solar install.
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Old 09-11-2016, 02:41 PM   #10
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I don't have a fuse there either. Wondering as well now.

At some point there was a very large batch of bad automotive blade fuses that went into circulation; they would cook rather than blow. Might be worth testing one of the others and replacing them all if it behaves that way.
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