DC DIN rail breaker up in smoke and now looking for replacement

I have been using MidniteSolar breakers as long as Midnight has been in business , I had never had a breaker failure. These are magnetic/hydraulic unlike the ones sold on amazon (thermal) A thermal breaker measures current by using a undersize peice in the circuit (internally) to measure the current resulting in higher breaker temperature.

Quality Industrial equiptment uses magnetic/hydraulic breakers for reliability

All of Midnight’s breakers are magnetic/hydraulic....the din rain ones are sourced from Circuit Breaker International and the panel mounts are Carlingswitch

I think your ferrule connection resulted in uneven contact area on the breaker terminal. I am surprised that a 10A load on a 30A device would overheat to that degree though.

Can you take a picture of the terminal-- a "wire's eye view"? (There wasn enough insulation to get a good sense of heating issues for me.)

Even the terminal screw is discolored from the heat.

One last look revealed something melted in the bottom of the connection. Not sure what it is.

I'd also recommend Midnite (which are built/rebranded from a major manufacturer, can't recall the name). Buying a no-named/obscure breaker off of Amazon is also really risky and would never do it. Would also point out that that is a polarized circuit breaker meaning if it is not connected properly it may also burn up/catch fire if the breaker is tripped under load.

rhino said:

I'd also recommend Midnite (which are built/rebranded from a major manufacturer, can't recall the name). Buying a no-named/obscure breaker off of Amazon is also really risky and would never do it. Would also point out that that is a polarized circuit breaker meaning if it is not connected properly it may also burn up/catch fire if the breaker is tripped under load.

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Well, I certainly didn’t get this far into the build and all the wiring just to mess up the polarity so that certainly wasn’t the issue. I’ve been sitting in the same spot for more than 30 days and haven’t moved a thing. I do appreciate your response though and could see that being an issue for a first time installer.
The breaker I purchase was the same one that another well known YouTuber recommended and has listed on his website. Not sure why he would recommend a no-named/obscure one if that’s what it really is.

Breaker seem to be chinese counterfeit/clone of Shneider Electric breaker.

Couple of options here:
A screw not torqued properly.
B proper torque but the thread is so bad that torque doesnt produce clamping.
C internal heating in the breaker (teardown photos of the breaker would help here)
D ferrule inserted on wrong side of the cage clamp. Seems stupid but I have seen this more than once. Even tightened by turning the screw counter-clockwise.

My first suspect would be chinese fake circuit breaker… after all it only needs to look like real circuit breaker.

How many amps do you think this takes before tripping:

rhino said:

I'd also recommend Midnite (which are built/rebranded from a major manufacturer, can't recall the name). Buying a no-named/obscure breaker off of Amazon is also really risky and would never do it. Would also point out that that is a polarized circuit breaker meaning if it is not connected properly it may also burn up/catch fire if the breaker is tripped under load.

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The Midnight din rail breakers are manufactured by Circuit Breaker International in South Africa. It is certified by CBI to 125 volts DC and recertified in the US to 150 volts DC by ETL (Electronic Testing Laboratories) to UL standards

These do have the CBI name on them and a sticker that attests to the Midnite re-certificatan to UL standards.

I have torn open quite a few Chinese circuit breakers and it’s scary, some have only a small guage wire as a fuse element....A fire waiting to happen

RandyP said:

How did you install the ferrule on each wire. Was it crimped to the wire ?

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400bird said:

don't see any indentation/deformation from the screw terminal getting tightened onto the ferule

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I don’t know everything and I’m looking at pictures on my phone but that shows every sign of a bad connection creating heat, oxidizing, getting worse, then finally arcing to failure. I’m thinking it was bad between ferrule and SCC but it’s possible the ferrule crimp was insufficient- can’t tell from the pic. I’m just betting on the ferrule not fitting well from what I see.

RVLiFe said:

Are these any good?

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I have seen three of them, never taken one apart. But the chaitaxi brand appear to be properly constructed and weigh a tad more than the cheapos I wouldn’t install.
My solar strings won’t ever be over 5.x amps with this camper setup however. The strings maxed at ~94VDC last winter. I used a 63A version as a battery disconnect last winter without any heat and ~44A charging with 2ga wires- and again no warmth/heating any time I checked. So it’s empirical that chaitaxi is ok but we don’t know what future shipments might bring. If I order more I’ll examine them quite closely and advise you to do the same.

Shimmy said:

am surprised that a 10A load on a 30A device would overheat to that degree though

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I have seen automotive consoles where phone charger cords contacted something metal and melted and/or ignited stuff. 2.1A. So I’m not in any way surprised other than surprised it wasn’t worse.

I have used bare-crimp butt connectors as ferrules (probs not a good idea- do not duplicate) leaving one end empty of wires and crushed them into a terminal connector on an Epever SCC. I tightened them, removed, reinstalled, retightened them three or four times to convince myself they wouldn’t loosen. They never got warm never mind hot. But with the tiny screws on Epever terminal inputs (and they don’t have parts) I didn’t like it; a hard ‘proper’ ferrule would require at least as much or more torque on the screw and I wouldn’t like that either. The MPPSolar aio has nice terminal connectors imho

Maybe OPs case is different but I was convinced I got as good a connection on bare wires inserted into the connector- but I also oversized these wires so I actually had to pinch them a tad square to even insert them into the connector on the SCC. Perhaps crimping a fat short (6ga or whatever the largest gauge that will barely fit the SCC terminal connectors) onto the solar wires and connecting those instead?

I am not going to use these ferrules in the replacement breaker.
I just made a new end with a short piece of the same wire I had laying around. Put on a new ferrule and tightened it down on the old breaker using one of the good connection points. I cranked it down as hard as I could using a large screwdriver. I’m pretty sure it was tightened down well over 10 foot pounds at the very least.
I was able to pull the wire completely out of the ferrule using some significant force but still, it came cleanly out. This should not have happened and didn’t give me a good assessment of the crimper I used so I certainly do not recommend using an inexpensive crimper. Actually, it’s going in the garbage.
I retested with bare wire and I can not pull it out by hand to save my life.
I realize that this was probably an extreme test and one that these connections would never actually be subject to since everything is tied down and secure but it still gave me great pause.
Mostly, I wanted to see how much I could crank the screws down before I broke anything. The answer to that is as hard as you can.
Lesson learned here and I’ll be taking the rest of the ferrules off. Not because I don’t trust the ferrules but because I don’t trust the crimper that was used.

Thanks everyone for the recommendations and enlightening me about the dangers of cheap breakers. I’m going to purchase a high quality crimper and revisit this test to see what happens.

Might make an interesting video for @Will Prowse to review using cheap crimpers and tools instead of quality ones. I think he would have a lot of people buying off his affiliate links. I know I would.

Edit: Just ran the test four more times and twice the ferrule came off the wire and twice the ferrule came out of the connector along with the wire. I could not pull a bare wire out of the connector unless I used a vise. And even then, the wire was flattened leaving much more surface area for contact then what using a ferrule provides.

My ferrules all came from FerrulesDirect.com. I've had no problems with my ferrules. They are not thin walled, they seem to crimp well. I test every crimp with a tug on it like my life depends on it. I do leave a small amount of wire sticking out the end of the ferrule, but maybe not as much as RVLife is showing in his pictures.

I have a hex crimper that came from FerrulesDirect.com also. It produces some very nice crimps. I initially regretted purchasing it since it was so expensive. But I have a few device terminals that need a round crimp and what this tool produces works great. A square crimp probably would not work in these terminals.

For the larger wire (6 gauge) I use a "square" crimping die and ratcheting crimper from eclipsetools.com. The crimps are more rectangular than square. The result is only as good as the operator. Not enough force and you get a crimp where the wire pulls out easily. However, if you're using a ferrule that isn't quite right for the wire gauge the result can be the same no matter how much effort you put into the crimp.

All my wires going into and out of the circuit breakers (on DIN rail) are secured with strain relief to ensure there is no movement of the wire in any direction. I have similar double pole circuit breakers that RVLife is posting pictures of (C65H-DC), but a different brand. Two years in, they're working well. However, if I have any doubts about them, I'll be switching to Midnite Solar breakers. I have a couple of the single pole Midnite Solar breakers on DIN rail that I'm using as OCP/Switch for 12 volt DC heaters. The polarized nature of the breakers is a challenge. Half the time I don't know if I have it wired the right way and end up finding the installation guide on their website.

What is the incentive to use ferrules on these connections? I know there are times when they are needed (namely fine stranded wire with a screw terminal), but in general they just add another contact surface and increase resistance. I hadn't thought of them as also being an additional point of failure as well.

Shimmy said:

What is the incentive to use ferrules on these connections? I know there are times when they are needed (namely fine stranded wire with a screw terminal), but in general they just add another contact surface and increase resistance. I hadn't thought of them as also being an additional point of failure as well.

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Insulated ferrules make the termination a little more resistant to wear and tear from vibration in a mobile environment.
The stranded copper gets less stress as the "boot lace" connects the terminal to the wire insulation.

In both stationary and mobile applications it also pretty much eliminates the chance for a stray wire strand shorting to an adjacent terminal.

After removing all the ferrules and connecting everything together again using the bare wire, I couldn’t be happier!

Previously, I used to get a pretty big drift between what the victron SCC stated as battery voltage and what the SmartShunt said the battery voltage was. Many times my battery would sit at 13.4v at 80% battery capacity and the SCC would go into absorption mode because the SCC saw the battery voltage jump up to over 13.8 volts while charging. Now, they are both reading battery voltage within .04v of each other instead of .4v or more at times.
I would never had expected it being the ferrules and/or a bad connection causing this.
Wish I would have known about all this previously but I’m glad I got it sorted.
On another note, at least the breaker that I purchased did it’s job and terminated the connection when it detected the poor connection. At the very least it did it’s job so actually, I wouldn’t hesitate to order a new one of the same kind. I haven’t done so yet but I’m still considering all the options on a quality one and so far the Midnight ones are the favored ones.

use of ferrules is mandated in canada and some european nations.

RandyP said:

use of ferrules is mandated in canada and some european nations.

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This is why I would like to see someone actually do a high quality test on them and look at voltage drift, surface area loss, material conductivity as well as different quality of crimpers and crimps that should be done. Many opinions out there but facts are facts. Trust the science right?

tomy2 said:

when I tightened the wires, the plastic body split at the seam.

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Just hearing that makes me want to stay away from it. Far away.

John Frum said:

Insulated ferrules make the termination a little more resistant to wear and tear from vibration in a mobile environment.
The stranded copper gets less stress as the "boot lace" connects the terminal to the wire insulation.

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Isn't that more of a call for strain relief than trying to treat the terminal as a structural connection?

RandyP said:

use of ferrules is mandated in canada and some european nations.

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In what applications though-- I get fine-strand wire with set-screw terminals needing a ferrule (ideally a pigtail though), but struggle to understand why you would use one for a compression plate design. I also understand the logic of tinning the tip of a wire to keep the strands together, or using any number of different crimp lugs for controls.

Most terminals rely on some level of deformation to provide adequate contact area, and a ferrule makes that harder to do.

RVLiFe said:

Just hearing that makes me want to stay away from it. Far away.

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Yes, I guess I answered my own question, maybe just wanted some collaboration, thanks. What did you use as a replacement?

tomy2 said:

Yes, I guess I answered my own question, maybe just wanted some collaboration, thanks. What did you use as a replacement?

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Haven’t bought anything yet. Temporarily hard wired to SCC with no shutoff. Still waiting for other opinions on here other than midnight solar. Has to be more than one option right? Seriously even thinking of going back to what I had. After all, it did terminate the connection and didn’t cause a fire. As a test, I set the screw as hard as I could on the defective unit and it held up great.
This breaker was also recommended by others and knowing now how it performed, I’d have no problem buying it again knowing that it was most likely my ferrule or loose connection that cause the issue.

2P 250V Low Voltage DC Miniature Circuit Breaker for Solar Panels Grid System din Rail Mount C65H-DC (32A)

Correctly installing copper wires into terminals involves several retightening. I do not use ferrules on my system and have never had a connection failure......BUT.....I have found the screw terminals will be loose in less than 20 minutes due to the fact that pure copper wire does compress over time. I always go back and retighten all screw connections at least after the first hour of operation, and again after a very hot spell producing high power. Im running 40-60 amps from each combiner into each charge controller.

I cannot even remember just how many system failures that I have found in high power electrical systems, way too many to count.

Lots of years in the electrical industry has taught me to look at first inspections for loose connections in system failures.