DC 12v "main" panel and "sub" panel?

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DC 12v "main" panel and "sub" panel?

Postby nrhmaine » Fri Jan 27, 2023 1:03 pm

It'll be a long time until I'm putting in electrical panels, but I need to have my wiring planned out so that I can do the rough wiring in the ceiling soon.

My battery and main distribution will be in a tongue box, and originally I planned to run all 12v circuits from there, through the ceiling, and out to the various switches and fixtures in the trailer.

Today it occurred to me that it would shorten all the wire runs, and decrease the number of wires going from tongue box to camper if I had a separate distribution panel in the camper.

So, does it make sense for me to have basically a main and sub panel arrangement for my 12v distribution? There would be an ATC fuse block in the tongue box, serving a couple nearby circuits. One of those circuits would be a 20A circuit with 10ga wire going into the cabin to supply another fuse block inside the camper. Branch circuits would come off that cabin fuse block (fused down to 5a mostly) and using 16ga wire to feed lights, receptacles, etc.

So, any thoughts on the two options?
Plan A: Run every circuit from the fuse block in the tongue box
Plan B: Supply a second fuse block in the cabin from the tongue box main block, and run most cabin circuits from the second in-cabin fuse block.

Thanks for your input!
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Re: DC 12v "main" panel and "sub" panel?

Postby tony.latham » Fri Jan 27, 2023 3:18 pm

That's probably the way I'd do it --a separate fuse box in the cabin and distribute from there.

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Re: DC 12v "main" panel and "sub" panel?

Postby kmack67.km » Fri Jan 27, 2023 4:14 pm

I would go for option B as well (a separate distribution panel/block in the main cabin). While you are about it, I would also consider running a conduit or two, from convenient places in the front and back of the trailer before you finish the ceiling,.... to make adding future circuits easier.

Best regards,
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Re: DC 12v "main" panel and "sub" panel?

Postby nrhmaine » Fri Jan 27, 2023 5:34 pm

Great, just making sure that what makes sense to me isn’t misguided. Sounds like I’m on the right track.

For the main wiring bundles, I plan to run them in black polyethylene water supply pipe up through the spars (bendable, smooth interior, thin walled). I’ll run individual conductor pairs to lights etc without conduit. It’s my compromise between some amount of serviceability down the road, and not going completely nuts by trying to provide 100% access and fish-able chases.


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Re: DC 12v "main" panel and "sub" panel?

Postby tony.latham » Fri Jan 27, 2023 8:03 pm

I plan to run them in black polyethylene water supply pipe up through the spars (bendable, smooth interior, thin walled).


I think putting your wiring inside poly pipe is as necessary as running conduit inside a closed house wall.

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:thinking:

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Re: DC 12v "main" panel and "sub" panel?

Postby nrhmaine » Fri Jan 27, 2023 10:06 pm

My only reason for pipe would be to provide a way to replace a wire, or add one down the road. It seems unlikely that it would be necessary (wires don’t really wear out) but if I miss something in my plan, or nick a conductor during sheathing, I worry I’d be really stuck trying to service a buried wiring run.

Do you think it’s unnecessary because later service is so unlikely? Or because you have another way of maintaining serviceability?


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Re: DC 12v "main" panel and "sub" panel?

Postby tony.latham » Fri Jan 27, 2023 11:22 pm

Do you think it’s unnecessary because later service is so unlikely?


I do. Ensure you've got USB outlets where you'll stash your phones at night. I wire in a double 12 Volt outlet at the back of he cabin that I'll stick a USB adapter in for whatever comes up (drone, dog collars, or USB-C for my computer). One switched light in the cabin and one in the galley. Wall switches aren't needed in a tiny cabin. And a USB outlet in the galley is a good idea.

If you're concerned about future needs, run the wire now, and don't fuse it.

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Re: DC 12v "main" panel and "sub" panel?

Postby Squigie » Fri Jan 27, 2023 11:39 pm

Sub-panel is not a bad idea.
"Conduit" is also not a bad idea.

I don't think either is this particular fuse block, but I have two "Blue Sea" fuse blocks in the parts box for wiring.
https://smile.amazon.com/Blue-Sea-Systems-Blade-Block/dp/B001P6FTHC/

I like breaking out chassis wiring from cabin wiring on things like this.
Having the "cabin" sub-panel only handle things inside the box means I can make the main panel handle "everything" closer to the battery. -Like a house breaker box being within reach of the main breaker.
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Re: DC 12v "main" panel and "sub" panel?

Postby tony.latham » Sat Jan 28, 2023 12:07 am

"Conduit" is also not a bad idea.


The issue I see is that it will eat 5/8" or so into the spars.

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Re: DC 12v "main" panel and "sub" panel?

Postby nrhmaine » Sat Jan 28, 2023 7:21 am

I’d plan to drill through the spars so that strength isn’t compromised


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