30amp Chassis Mount Fuse

[AlexPeterson]

I've begun doing a number of electrical mods on our new 2500RL, which I will write up in a separate thread in the coming days. However, I'm curious about this. There is this 30amp fuse bolted to the chassis. A few things come off on the battery side of the fuse, but the #8 wire, which presumably goes to the power center/converter via the battery "disconnect" switch, is on the fused side of this. It would seem to limit (when not on shore power) the current used by the power center to only 30amps, which doesn't make sense to me. What am I missing? I know I do not have all of these correctly identified, but...

howson I have studied your post #7 in this thread also, thanks.



The chassis mount fuse:

[howson]

AlexPeterson

First--a minor terminology clarification. The device in the pictures is a self-resetting circuit breaker (SRCB), not a fuse. Should the SRCB open you'll hear it go "snap!". Once it cools power will be restored automatically without any intervention on your part. If the overcurrent condition persists, the breaker will again open (and you'll hear the "SNAP!" again). The cycle will repeat until the breaker fails or the overcurrent condition is eliminated.

On the gold (input) side of the SRCB I agree with the labeling as shown in your pics. The devices connected (tongue jack, breakaway, etc) are not protected by the breaker. The breaker's post is used as a convenient connection point.

On the output (silver) side of the breaker it can get a bit confusing because power can flow in (to) the battery or out (from) the battery via the SRCB.

Consider the black 7-pin power connector. That wire sends power from the truck to the battery (a "trickle" charge) while towing. At least in my Ford, reverse current flow (from the trailer to the truck) is not allowed (probably a diode circuit or relay) when the truck is not powered on and the 7-pin is connected between the two vehicles. The point is the wire has no affect on the 30A available to the trailer while camping.

The red solar wire and how current flows can be a bit confusing. Consider a situation where you're not connected to shore power. If that wire is connected to a solar controller, at night (or when there's no generation of solar power aka "PV") there is a very small amount of current flowing from the battery to the controller. If PV is being generated and the battery can accept the charge, current is flowing to the battery from the controller through the breaker.

This is also true for the wire that connects to the Power Distribution Panel (PDP). If the trailer is connected to shore power, excess power not being consumed by 12v components will result in current flowing from the converter to the battery (if it will accept a charge). If the trailer is not connected to shore power, current will flow from the battery to the PDP for lights and all the other 12v components powered from that central location.

I'm getting deep in the weeds and may have already lost some readers (sorry!). The bottom line is at any given time power could be flowing to or from the battery via some of the wires on the silver side of the breaker.

To specifically address your concern, with the exception of the 50A SRCB on the hydraulic system of the larger GD units (that needed an 80A breaker) I do not know of an issue where the breaker provided by GD didn't provide the protection or power to the camper required at it's given rating.

Also--if my .02 means anything(!), kudos for tracking down and labeling the wires on your trailer. At some point in the future there will be a problem and because you're taking the time to figure out the wiring now fixing the future issue will be a lot easier.

Howard

[AlexPeterson]

howson Thanks for the very thoughtful reply! I did learn it was a CB after I posted... I will need to reconfigure things somewhat as central to this project is installing two 100a-hr lithium batteries which can take a lot more charge than the 30a that the SRCB will tolerate. Situation: Let's say nothing in the camper drawing notable power save for maybe the frig (12v compressor). Batteries low, plug into shore power, bright sunlight, newly upgraded converter now capable of 50a (on lithium setting). As configured from factory, this won't work as the 30a breaker may be overloaded. I'll need to ponder a bit... I'd like to insert the (non-inverter) battery lines right back into where they were, but this size breaker make that seem problematic.

Not for now, but I will be redoing that mess under the trailer in the next year or so before it turns to copper oxide. I'd like to bring them all up into the storage area, but first I want to finish the battery/inverter/transfer/DCDC project.

FWIW, I'm not intimidated by any wiring - I worked many summers as an electrician, and also did a little re-wiring a few years ago on a different vehicle:



And, after a little taming, but still not finished:

[ncitro]

AlexPeterson Sounds like you are on the right track. I eliminated the SRCBs in my fifth wheel (and my father in laws bumper pull trailer) and replaced them with a fuse panel. Not as easy to reset as the SRCB, but much easier to add additional circuits and keep track of the wiring. I tied my chargers (100A Solar Controller, 40A Renogy DC to DC, and 100A backup converter) to high current buss bars (250A) and then from there to the batteries. The Victron MultiPlus I tied directly to the batteries. All of these were located in close proximity to the batteries to limit voltage drop. Here is a photo, this is before I cleaned up the wiring, and before I added two more batteries. You can see the fuse panel in the bottom right.

This is the fuse panel I used:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

You will have to watch some of the larger loads, I think I had a couple 50A SRCB, so I fused those separately outside the panel to stay within its ratings. If your biggest is 30A you should be okay.

[AlexPeterson]

ncitro Neil, the fuse panel is a great idea. Turns out I have a great spot for an 8 circuit one rated 100a. Then the only stuff which will remain down under (for now...) will be the 7 pin cord termination. Project scope creep...

[ncitro]

I understand that problem deeply. Good luck!

[Jlawles2]

You could split out the various circuits like they do on the larger units. On our 303 there is a bus bar with multiple circuit breakers on it.

Nice job on that small wiring mess converting it to a nice looking layout.

[AlexPeterson]

Update: I could not stand those hot connections under the trailer waiting to corrode, so I did bring them up inside the storage area. More to come on this project, but here's an updated annotated picture of what those wires under the trailer were:

[AlexPeterson]

Final update on identification of these wires, in case it is of help to someone.

[Yoda]

Final update on identification of these wires, in case it is of help to someone.

Alex I asked in the other thread about the black and yellow wires that are connected to the chassis bolt. Do you know where they come from? Normally the negative return wires are white. The black wire is a mystery as they are usually hot (positive) along with most colored wires?

ON edit Does the black have a white stripe? Even so it's usually hot elsewhere.

Just asking
Thanks
Keith

[AlexPeterson]

Keith - I'll do a little digging tomorrow and take some pictures as I can, given I've bundled everything up already. But, those wires are exactly what were on those locations, minus one red and one black which went to the battery, which were already removed at this photo's taking.

I'm 90% sure (and can be 100% tomorrow) that the black wire is the solar ground. The little fringe on the black wire is red, from the tear away residue (it was joined/paired/whatever they call it to the red wire).

Alex

[acoleman43]

Project scope creep...

lol...so true...