12V circuit breakers in series?

[happy2rv]

I was putting a battery disconnect on my trailer this afternoon and noticed this:


Click For Full-Size Image

I'm not sure what the point of having two circuit breakers in series like this is, especially since the first one connected to the battery (the one at the bottom of the photo) appears to be shorted out. They appear to be the same size breakers. :h

This came from the factory like this unless the dealer did something before delivery. I'm the original owner and it hasn't been in the shop for any type of electrical work since I've owned it. Am I missing something?

[BFL13]

You need some red tape to wrap around that white wire, so there will be no confusion later if you have to replace things.

[beemerphile1]

Not in series, mine is similar. The 50a is the main breaker and the 30a is for the slide. A jumper ties them together.

[BB_TX]

My 5er has two auto reset circuit breakers like that. Battery wire goes to one with a jumper to the other. Each breaker feeds its own circuits. A smaller wire also comes off the battery jumper wire, but has an inline fuse for protection of that circuit.

[time2roll]

happy2rv wrote:
I don't believe these are meant to be the primary fuses. I think they are more of a safety than anything.

Have you seen what often happens to these self resetting circuit breakers when they continue to cycle?
Again I assume they are self resetting. I would replace if they are.

[happy2rv]

I was finally able to see current ratings on them and the first is a 50A, the second is a 30A. So that makes a little more sense.

time2roll wrote:
My first concern would be the smaller white wire connected direct to the larger red wires.
Second concern is that these self resetting breakers are even used at all. I would replace with Bussmann Hi-Amp.

I don't believe these are meant to be the primary fuses. I think they are more of a safety than anything. Most of the wires feed things with fuses inline. For instance, the tongue jack has a fuse in the line before it gets to the motor. The load center obviously has fuses for each circuit that it feeds. I'm not too sure about the other smaller wires. I'm sure one of them feeds the electric brakes. There are probably fuses in those lines as well, buried somewhere in the depths of the underbelly or hidden in a cabinet somewhere. This is one area where the RV industry does and extremely poor job. I don't think any two RVs that come off the same assembly line are wired exactly the same. The wires go here and there whichever way they decide to run them that day and they hide things like fuses, taps, and splitters in the strangest places. I had the surround trim off of the bathroom fan a couple of weeks ago because I wanted to run a separate wall switch for the fan and I found the TV cables splitter tucked up in the ceiling beside the bathroom vent. That's exactly where I would have looked for it, NOT.

The "mystery" white wire runs to a home type metal electrical junction box screwed to the side of the trailer that holds a bunch of wire junctions. This is where the 7-way tow cable hooks up, so I'm sure the white wire is among other things, the charge cable from the 7-way. I didn't have time to sort out the what else it feeds, but it's tied to junction of at least 4-5 wires. It would make more sense to me for them to have put an actual weather sealed load center here with fuses and labeling like they do under the hood of all cars. I suppose it would have cost more, but it seems like that would be farm more reliable than the crimp connectors they used.

dougrainer wrote:
It is miswired...

Doug, thanks. That makes a lot more sense to me than the way it's wired. I'm assuming the white wire which, as stated above, I'm pretty sure is the charge wire from the 7-way among other functions should move with the red wire to the top post of the bottom breaker.

[MEXICOWANDERER]

The shift-end bell had rung.

Gotta little rushed on the common red + feeder battery wire.


Que sera sera

[wnjj]

time2roll wrote:
Unless all wire connections, sizes and ratings are given this is just a guess.
My first concern would be the smaller white wire connected direct to the larger red wires.
Second concern is that these self resetting breakers are even used at all. I would replace with Bussmann Hi-Amp.

Maybe the white wire goes to the breakaway switch? You want it wired as electrically close to the battery as practical to minimize the chance of it failing.

[time2roll]

Unless all wire connections, sizes and ratings are given this is just a guess.
My first concern would be the smaller white wire connected direct to the larger red wires.
Second concern is that these self resetting breakers are even used at all. I would replace with Bussmann Hi-Amp.

[dougrainer]

It is miswired. It happens. The large Red that loops from the bottom breaker lug. THAT wire should be on the very bottom with the other large red wire. You then remove the Upper breaker LARGE red wire and put it on the now empty post of the bottom breaker. This will distribute the load and protection correctly. Doug

[happy2rv]

I verified that the red wire coming into the first breaker at the bottom of the picture is the power from the batteries. The red wire in going from the top breaker is the load center inside the RV. The black wire at the top is my electric tongue jack.

The white wire is definitely not a ground wire. I haven't traced down everything it powers yet, it goes to a junction box on the trailer frame. I also haven't traced the white with blue stripe.

I don't see a rating on the breakers, but they appear to be identical.

[wa8yxm]

The breaker with just 2 wires is a "MAIN" same as the MAIN on your 120 volt panel. the breaker with several wires hooked to each lug is a "Branch" there are other branch breakers hooked to one of the lugs.

[cavie]

Not is series. Red wire is hot to battery. I don't think the white wire belongs there.

[BB_TX]

happy2rv wrote:
...

BB_TX wrote:
Curious why you think the one is “shorted out”. If the breakers are good you will have +12 vdc on both posts at all times except when they trip.

If you look at the full size picture, it's clearer. The ring terminal on the upper post of the bottom breaker is touching the bottom post.

Ahh. I missed that. That bypasses that breaker. If it came new like that then it would not surprise me if they were also wired wrong.

[happy2rv]

BFL13 wrote:
Not in series. Looks ok except the mystery white wire in with the reds at the lower terminal of the upper CB. White is usually neg.

As far as I can tell, there is no concept of color code in the RV industry. At least they used red and black for the main battery cables. Every interior wire I've seen has been white, occasionally with a stripe.