Putting POWER to the trailer.

[Dirtytires]

I need some advise on performing this operation. I am melting wires and fuses left and right.

Setup:

I have one deep cell Marine battery.
I have attached to the trailer a fusepanel.

I keep burining wires when I wire the lights up?

Do I need to have a fuse between the battery and the fusebox?

Current Configuration:

I have one battery grounded to the trailer..
I have the positive wire from the battery lead to the fused junction box.
I have the box grounded to the frame of the trailer as well.

When I place the tester light on the wires from another tiedown in the box it does not have power.
When I place the tester light on the power feed it works. So how do I isolate the wires . Isnt that
what the fuse box is used for? I keep blowing fuses and burning the "test " light.

The goal is to have a few interior (led lights,and a water pump, ) powered by the battery.

Thanks,

Craig

 

[dwh]

The purpose of a fuse, is to protect the wire by melting before the wire does. Every circuit should be protected by a fuse. The fuse normally goes in the "hot" wire, so that when the fuse burns, the entire "circuit" (hot wire (+) / load / return wire (-)) goes dead.


There should be a hot wire from the battery to the fuse block - that wire should be protected by a fuse or breaker.

There should be hot wires coming out of the fuse block to feed various loads - each hot wire protected by a fuse in the fuse block.

There should be return wires from the loads, to the negative terminal on the battery. These do not normally need fuses, since they are protected by the fuse in the hot wire of the circuit.


Often, the return wires are omitted and rather than running them all the way back to the battery negative, they are connected to the vehicle frame, which is then connected to the battery negative. That way, the frame serves as the return wire for the circuit. This is poor practice, but it generally does work, and it's cheaper and easier than running a bunch of separate return wires, which is why vehicle manufacturers do it all the time.


Since the purpose of a fuse is to melt before the wire does, the fuse MUST ALWAYS be rated a bit less than the wire. So, say for #12 wire, which is rated at 20a, you would normally use a 20a fuse. The reason you can get away with that, is that the 20a rating of #12 wire is conservative - #12 can actually handle a bit more than 20a, so if the fuse burns at 20a, the wire won't be to the melting point yet.


The most common reason that wires melt, is that the fuse is rated higher than the wire. This makes the wire melt but not the fuse. The wire is protecting the fuse, which is backwards.


From what you describe, I would guess either that A) you've got something wired seriously wrong, or B) that you've got loads which are greater than the wire can handle, AND oversized fuses that don't protect the wire. I.e., a 10a rated wire, protected by a 15a fuse and more than 10a of load being fed by the wire.


A little 12v tester with a lamp in it, should not burn the lamp unless your wiring is screwed up so that when you use the tester, the tester becomes part of the circuit (and the filament in the lamp now becomes a fuse).


Of course, all of what you describe could also be caused by extremely crappy grounding - like...oh...using the frame or chassis as the power return path...

 

[Dirtytires]

I guess I need to get a breaker or fuse for the battery side. What size of fuse would I put in there? Would a 20 amp fuse be okay to place in the battery side?

Thanks for the helps.


Craig

 

[dwh]

The fuse must be the right size to protect the wire. To figure out what size fuse you need - you need to know what size the wire is, and what amperage it is rated to handle.

Then you know what size fuse you need to protect that particular wire.

If you are melting the wire from the battery to the fuse block - then you probably need a bigger wire. AND the right size fuse for the new wire.

 

[kevint]

Could you post a photograph of what you mean when you say you have the box grounded to the frame of the trailer.

Are you saying that simply by placing the test light on the fuse block and it blows a fuse and the light?

 

[Dirtytires]

the test light is just an old turn signal bulb. not an amp meter..
The fused box is grounded to the trailer. Along with the battery.
For the battery I used the same ground as the Military used when they had
the engne and ballasts grounded.

 

[Backroad Explorer]

Craig have you recently painted the trailer? If so try putting an external star washer between the frame connection and the cable end. It will bite through the paint to metal.

Hope this helps.

P.S. Why did'nt you run the ground straight to the battery along with the positive?

 

[sapper]

Also how many lights are you putting on one wire/switch and what is the wattage?

Here is how I wired up every vehicle I have ever done with lights but in your case you will need a fuse panel. I am very fond of the Blue Sea panels myself as I find them perfect for my needs.


I also use relays for each pair of lights I install to reduce the current through the switch.

 

[Dirtytires]

Craig have you recently painted the trailer? If so try putting an external star washer between the frame connection and the cable end. It will bite through the paint to metal.

Hope this helps.

P.S. Why did'nt you run the ground straight to the battery along with the positive?

Negative on the paint. As far as running the ground straight to the battery not sure why..lol

 

[Backroad Explorer]

Just curious,
I've always run pos. & neg. to the battery for all my accessory Fuse Panels same for radios C.B. or Ham.
I just don't trust the frame as a ground path.

 

[kevint]

Does the fuse blow as soon as you plug it in? Is the only load you have put on the system the test light?

 

[Dirtytires]

Sorry if this seems snarky or condescending,

If you are melting stuff as you say, Obviously something you are doing is SEVERELY wrong.
Maybe its best left to someone having more electrical expertise.
Without a picture or drawing and just based on your descriptions its real hard to understand what you are doing.

Anyway from your description, My first thought is something to do with your statement "I have the box grounded to the frame of the trailer as well."
This seems odd as typically an old-school automotive fusebox would have nothing grounded to it. (Of course its mounting screws maybe attached to a grounded surface is ok. But nothing of an electrical nature would usually be grounded)

The positive from the source(battery in this case) Comes into the fusebox. The only other connections out of the fusebox are the positive wires going out to the various circuits of lights etc.

And yes, You should have a fuse (or circuitbreaker) between the positive of the battery and where the battery connects on the fusebox.

Thanks for the reply. I understand what you are saying. Will work on getting some pictures.

 

[dwh]

Just curious,
I've always run pos. & neg. to the battery for all my accessory Fuse Panels same for radios C.B. or Ham.
I just don't trust the frame as a ground path.

It's not just about the frame being a crappy ground path. Sometimes it is, sometimes it isn't.

The other issue, is that the greater the distance (separation) between the supply wire and the return wire - the greater the inductance and the greater the chance of radio interference and/or noise. Best from an inductance point of view is when the two wires are physically twisted around each other - but as long as they are right together side by side, that's usually pretty good.

Using the frame for the return path, creates a lot more separation.

 

[Dirtytires]

The battery where it is grounded to the trailer.

The battery.

The fuse panel.

Fuse box Ground. I think this is the problem?

 

[Dirtytires]

I will put a 30 amp fuse on the battery, positive ; then continue down the line
and connect the battery positive to the fuse box.

Do I need to remove the ground wire that I put on the fuse box?
Then from the fuse box I can connect the water pump,radio,and the water pump.
Does this sound correct?