Fuse Box Wiring?

[LinearLynn]

hello! I am about to wire up all of our solar toys! I have one hang up though. I have the the blue sea systems marine fuse box, I know I need 4awg wire but everytime I go to Home Depot to get it they spin the rack and 4 looks too thin.... any tips? Or where I could order it?

[TimC]

Question...

What gauge wire are you using from battery to fuse box? 4AWG? 4AWG is capable of pulling 85 amps. That's A LOT for a teardrop trailer. Just trying to understand why you are using 4awg.

Can you describe your solar system as far as panel wattage, charge controller amperage, battery bank size and voltage (assuming 12v).

[LinearLynn]

I was going to use 4awg with plans to place the fuse box very near the battery.

[jgizzi]

I am not sure that I understand what you mean by "they spin the rack" nor am I sure that you mean 4 awg cable. That would be huge for our needs in a teardrop. 14 sounds more reasonable. Also note that you will want to use stranded wire rather than solid.

[tony.latham]

Are you sure you are looking at 4 AWG??? That stuff should look fat. If it's a bulk spool, there should be a label on the side.

I use 12 AWG from the battery to the fuse box. That allows me to pull 20 amps and I'll never come close to that kind of load. My 130 watt solar system uses 14 AWG.



I'm with Jim, by the way... spin the rack?

Tony

[TimC]

As Jim states, 14 awg will handle 15amps. Unless you have a very unusual teardrop electrical system you are way over gauging.

I have 200 watts of panels going to a 30amp charge controller and rarely see 10 amps of production going to the battery. From the battery I have 14awg going eight feet to my fuse panel via a kill switch. It is fused with a 15a fuse at the battery to protect the wire.

Go with 12awg if you have a normal teardrop load. I used 14awg OFC copper wire (OFC = Oxygen Free Copper - true copper with extra flexible sheathing. CCA copper is copper clad aluminum or similar).

[LinearLynn]

Ok. Thank you for all of your feedback! We have a 6.5x12 cargo trailer that we are going to be living out of come Jan 2022. We have a build journal but I'm not sure how to link it in this post.

Here is my solar diagram draft #3. I know I may be oversizing a couple things but I want the potential to add another solar panel/battery eventually without rewiring the whole system. To start, we'll only have 12 v power, but I picked up that inverter extremely cheap and would like to wire it up too. I've listed the wire sizes & fuse sizes I have. The only one I'm not sure of is the gauge from battery to fuse box. I am (obviously) a beginner! So open to any opinions/advice y'all have.

At Home Depot they have a huge wall of wiring they press a button and it spins around and around to find what wire size you need - that's what I'm referring to.




Thanks!!

[LinearLynn]

Oo that photo came out very blurry. Let's try this one

[cwaet]

While not as convenient as Home Depot, I found that PKYS had almost all of the wiring, breakers, switches, etc that I needed for my build for cheaper than I could find the same elsewhere (West Marine has the same stuff I think) and I could buy large size wire by the foot. I got the lugs, heat shrink tubing, etc from Grainger. Just wired the trailer all up this weekend and was really happy with the quality. I used 6 AWG from bus bar to DC fuse box as I had some extra from the charger/converter, and then Ancor duplex 14/2 to most of the various items (lights, DC USB outlets, etc) with a few runs of 12/2 to others (fans, water pump). Hope that helps!

[tony.latham]

Three things jump out at me.

1. A 40 amp breaker protecting a 10 AWG wire from your panel. It should be a 30 amp breaker. But why that heavy of wire? You'll actually get about 6 amps from your single panel at solar noon, not the 7.9.

2. The wires from your controller. The positive is 10 AWG and the negative is 4 AWG. They should be the same and 4 AWG is gross overkill. 12 AWG for both is fine.

3. A 40 amp breaker on a 10 AWG wire (again).

Make sure add a battery meter such as the AiLi.

Tony

[LinearLynn]

Three things jump out at me.

1. A 40 amp breaker protecting a 10 AWG wire from your panel. It should be a 30 amp breaker. But why that heavy of wire? You'll actually get about 6 amps from your single panel at solar noon, not the 7.9.

2. The wires from your controller. The positive is 10 AWG and the negative is 4 AWG. They should be the same and 4 AWG is gross overkill. 12 AWG for both is fine.

3. A 40 amp breaker on a 10 AWG wire (again).

Make sure add a battery meter such as the AiLi.

Tony

1. Got it, I'll switch to 30a, you're right & I understand.
2. It is the same 10awg, my chart is just sloppy. Good to know about 12, cheaper and easier to work with, I'll make the adjustment!
3. I already hane a battery monitor & shunt in there. Though it isn't that brand.

Thanks for taking the time to read my post!

[Pmullen503]

It's bad practice to over-fuse any wire or device. Putting too large a fuse on a line means the device or wiring you have is protecting the fuse not the other way around.

Size your fuses so it's the weakest link in the system. That way the fuse protects the wiring and the device.

[featherliteCT1]

That is a big inverter.

A 1000W inverter is capable of drawing over 80 Ah out of the battery. If the inverter is 6 feet away from the battery, you would need 4awg wire to handle those 80Ah, per the Blue Sea wire size calculator linked below.

http://circuitwizard.bluesea.com
Note that you need to input the combined total length of both the negative and positive wires into the calculator.

Both the positive and negative wires from the battery would need to be sized to the inverter. Also, the shunt would need to be sized to draw that much current, because that much current would be flowing through the shunt.

The fuse for the battery would need to be sized appropriately at 125% of the expected maximum current draw.

An electric coffee pot could easily draw 80 DC Ah.
If you wanted to power a device with an AC motor, like a small 120V refrigerator, the current draw could be three times the rated Ah.

In any event, your inverter current draws will determine the size of the wires feeding the inverter, the size of the shunt and the size of the fuse at the battery.

As others rightly pointed out, all the other wires would need smaller fuses matched to the applicable wire size, with each fuse sized appropriately at 125% of the expected maximum current draw.