Melted Breaker

[MambaJack]

My system has been running great for months.

I have a 60 amp 2 sided breaker (breaks both positive and negative) that connects to the 4 gauge wires coming out of my midnite solar 250 charge controller, onto the battery bank with 4 gauge wire also
Went to show the system to a guy i was camping with, and noticed a bad smell, along with a melted breaker.
I am trying to figure out what happened. The connectors on that breaker seemed pretty crappy when I installed them. is there a change the bouncing around of the back of the bus caused that negative wire to get loose and somehow arc from the breaker to it to cause the melted plastic maybe, or is could it be a faulty breaker?

Also, suggestions on what to replace with?
Thanks

[bob-n]

You'd have to be a really good diagnostician to figure out the root cause with certainty. But if I had to speculate, I'd guess that the connection was poor and simply got hot from the series resistance and high current.

My suggestion is to replace the breaker with a top-quality breaker, for example, a SquareD Qo breaker. Do an excellent job on all connections. If the panel is damaged, replace that as well. If in doubt, get an electrician to do it. Bad connections or incorrect connections could lead to fire and death. No joke.

Then, get a cheap non-contact thermometer and use it to check the temperature at all of the connections while running at high current, to make sure that you have it wired securely. Even better than a non-contact thermometer would be a thermal (IR) camera.

Also, get a clamp-on ampmeter and use it to make sure that all of the current levels are what you expect.

[SunEagle]

It could have been a bad breaker or the connections loosened up causing a higher resistance and more heat.

Oh getting a clamp on meter like bob-n suggested is also a good idea. For some reason more than 60amps may be going through that breaker which is designed to open due to short circuit and maybe not due to high amps over a period time.

[Mike90250]

Midnight sells good DC rated breakers. AC breakers are no good for solar.

Bad connection contacts will heat up and melt stuff, it happened to me in my pwr distribution panel, with a 6g DC line on a bus bar

[MambaJack]

Thanks so much guys. Didn't really like that breaker design anyhow. I also have one going into the charger controller from the panels, will be replacing it

[Mike90250]

forgot, here's a link to the midnight combiner

http://www.midnitesolar.com/productPhoto.php?product_ID=78&productCatName=Combiners&productCat_ID=9&sortOrder=4&act=p

and breakers that fit it ( $20 breaker, rated for switch duty)

http://www.midnitesolar.com/productPhoto.php?product_ID=183&productCatName=Combiners&productCat_ID=9&sortOrder=1&act=p

Solar DC rated fuse holders are $6, and fuses are $4 and you would still need a switch to turn things off with, so I really like the breakers

[bcroe]

A loose connection may have enough resistance to heat up, and the daily heat cycle
loosen it more, snowballs to a burned through connection. I burned out a couple
early on, went out at night and tightened everything a couple times a year. At first
things were not nearly as tight as I had done them. Half a decade later things seem
to have stabilized, no more hot spots or failures. good luck, Bruce Roe