Good wire gone bad

[Shockah]

Brings to mind the old saying "it happens to the best of us".

Glad to see it's ONLY a melted wire and nothing more serious.

[Mike90250]

Any short would have tripped a breaker somewhere. The midnight boxes are pretty smart that way. And since that's on the battery buss, a short would be more than spectacular. Till the 250A breaker blows.

#4 into a midnight buss bar, for a 6KW inverter, should have been OK. I'll call midnight and see what the valid range of wire is for the busses. But it sure did work like a heater! And it was coarse wire, not fine welding wire. So that should have been OK. And yep, the heat could have sized the setscrew into the tinned buss, and that's why it feels solid now. And the buss conducted enough heat to melt the insulation on the upper wire too. if it was loose 3 years ago, I'd have been getting the Battery Bus overvoltage warnings for a long time. Just started about 2 months ago. Could have been cold flow loosened the effective torque on the wire and it cascaded from there.

Anyone have any experience on the copper filled conductive grease ? Is it suitable for set screw terminals ?

[Sunking]

Crap they will not let all the pictures go.

DIY



Pro

[Sunking]

Is that all the way into the powered equipment, or is it also considered OK to crimp a ring terminal to a wire and attach that to a bolt?

That is a irreversible compression.

Here is the tool a DIY would use that cost him $10 at any Auto Parts or Electronic store.



Here is what a Aviation Mechanic or Professional Electrician might use. They are ratcheting and will not let go until you fully complete the crimp. It leaves a Die Mark with either a Letter, Number, Dots, or Symbol so an inspector can verify the correct tool is used. This one tool here made by T&B cost around $250 to $300.



And for wire over #6 AWG up to 750 MCM something like this that uses a hydraulic pump to deliver 15 tons of pressure. .

[ChrisOlson]

Then, when getting into the ePanel, to prep for the Midnight Controller for the new array, I saw the cause. And all the screws seem tight. Putting in new #4 wire (55A) and buss bar, and that should fix it up. Yow!

Looks identical to wind turbine wiring. Wind turbines can melt anything in sustained high wind.

That screw connection made a pretty nice resistance heater.

[inetdog]

They have to use irreversible compression connectors with calibrated and tested tools.

Is that all the way into the powered equipment, or is it also considered OK to crimp a ring terminal to a wire and attach that to a bolt?
I understand that a suitable connector will have very precisely engineered contact force and area, hopefully maintained through thermal cycling, but a bolt and locknut with Belleville washers should be pretty reliable too.
Those high current connector pairs can get really expensive really fast.

[Sunking]

I have also heard electricians say that once you have torqued down a screw like that on stranded wire, re-torquing it or removing and replacing the wire justifies cutting back the end of the wire so that you crush some fresh wire.

Well on ething every electrician will tell you is all mechanical connections will fail and the stats back that up. In addition a majority of all electrical fires are from poor connections. That is on ereasons utilities do not use mechanical connections. They either use thermal weld or reversible compression.

In addition the Air Craft industry prohibits mechanical electrical connectors. They have to use irreversible compression connectors with calibrated and tested tools.

[inetdog]

Wow indeed!

Just from the pictures, I would say that either the screw was not sufficiently torqued down or there were quite a few damaged strands in the wire where it came around the bend.

"Seemed tight" is the operative word here.
Once it has overheated like that, the screw could be binding rather than being fully tight.
I have also heard electricians say that once you have torqued down a screw like that on stranded wire, re-torquing it or removing and replacing the wire justifies cutting back the end of the wire so that you crush some fresh wire.

Also, did you confirm that the terminal is in fact rated for stranded wire in that size? I do not expect that it would not be, but worth a check.

[Sunking]

Somebody had a Short Circuit, or a poor connection and never new it. You got lucky it did not catch on fire. If it was from a short circuit you really need to look over your Over Current Protection scheme because something is wrong with it.

Just from looking at it and the location my guess is just a poor termination that heated up. Pretty classic burn pattern for poor connections.

[Mike90250]

Been getting high battery voltage alarms from the charge controller, and I went over all the battery interconnects and the terminals in the charge controller with an IR thermometer.

Then, when getting into the ePanel, to prep for the Midnight Controller for the new array, I saw the cause. And all the screws seem tight. Putting in new #4 wire (55A) and buss bar, and that should fix it up. Yow!

10259224_654873261252797_5715636728126544140_o.jpg

Photos here