Electrical Questions of the 12V variety - Fiberglass RV

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Old 01-03-2008, 01:43 PM   #1
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Fused Switch Block

The above link looks interesting. But I'm challenged in the wiring department, so I'm asking for help here. Would this item, work as a all-in-one connection box for the 12v system in the PP? If I have this figured out correctly, which I probably don't, I could use this to hook everything up to switches in a central location. Like so::

Lights and such >> fused switch panel >> battery >> solar controller >> solar panel(s).

I think, if I understand what I'm reading in the RV electrical book I bought, I can also have local switches at the light sources. So I could have the central box near the door and still be able to turn things on and off elsewhere.

Would the fuses at the switch box be enough or would I also need fuses elsewhere?
If I also want to separately wire a power inverter to the battery, do I need some sort of junction box? Or would I just have two sets of connector wires going to the battery?

My local community college is having intro to electrical repairs and plumbing repair in continuing ed this spring. I'm planning on taking both of the classes. So hopefully, I won't remain utter clueless forever.

Thanks for your thoughts on this. I hope to start order parts and pieces soon.

Plotting my next adventures...
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Old 01-03-2008, 02:59 PM   #2
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It appears that each switch has its own 10amp fuse and I also suspect that the switch might light up when the circuit is on. Yes, you can install another switch at the source where you want to turn the item on/off.

The fuse on the panel will protect the length of wire from the switch to the source however; you might want to install an inline fuse that protects the master +Battery Buss. That is the wire that runs to the switch panel from the battery. You will only run 1 wire to the battery and it will connect all panel + sides and you should have an inline fuse right before it connects to the panel.

It will be larger than 10A and the copper wire size from the panel to the battery should be rather big such as 12G, 10G or 8Gauge. (The bigger the better and the lower the number the larger the wire)

I have found that House Wiring, stranded copper, single conductor (Where there is only 1 wire) is far more durable than vehicle wiring. Vehicle wiring has a softer covering and the auto manufactures will wrap a loom or tape type of material over it in the bundle to give it more protection. The single conductor house wiring has a really tough layer with another clear layer over that.

Should you wish, send me an email with your information and I will send you samples of the different wires and you can make an informed decision.

Remember: You will need to run a 2nd wire to the fixture and you can run it from the fixture to the frame, you will not have to run it all the way back to the panel as long as you connect the negative () side of the battery to the frame.

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Old 01-03-2008, 09:07 PM   #3
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I actually used a similar unit when I rebuilt my Compact Jr. Mine was a 4-circuit unit, which I used to power strategically located 12 volt (cigarette lighter type) outlets. You can see it in the upper left of the 2nd photo.

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2 circuits had 2 outlets per switch, and 2 circuits had 1 outlet per switch.

The yellow fixtures are actually Flashlights I bought at WalMart. Mine came with 12 volt cords that could be used instead of batteries. The Lighting outlets were mounted in electrical boxes high over the front window and rear entry door. 4 "Flashlights" set on fluorescent bulbs lit the whole trailer. (One was located in my "privacy room" where I had the porta-potty.) I used the incandescent bulbs in the flashlights pointing down as reading spotlights.

One switched outlet was for my Igloo Thermoelectric Cooler. The last switched outlet was "just in case" and I never actually used it.
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Old 01-04-2008, 10:48 AM   #4
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I used a very similar four switch in my Scamp redo. We control all the 12v lighting from the dinette side of the overhead cabinet so if the kids are reading at night and fall asleep we can shut their lights out without having to get out of bed. All the 12V lighting also has a local switch as well.

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Old 01-04-2008, 06:06 PM   #5
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You can use the fused switchbox you show as others have said. I have used some variety of them in each of the rigs I have had and they are very convenient.
I also use a master battery cut-off switch and a large main fuse ahead of the box.

Then you can run circuits to the loads/lights/outlets and either let them be switched by the box or provide extra swithes if more convenient. It does seem a little much though in a tiny trailer that you would need more switches but that also depends on just how many switched loads you need.

On the other hand......you do not want to use ordinary solid conductor house wiring and you will want to run both a hot and ground wire to each load. Luckily twin conducter wiring is both available and inexpensive.

I don't want to sound too obnoxious is disagreeing here but there are definite reasons why automotive and marine wiring is stranded and not solid. Also different insulation types have widely different qualities than seems obvious from just using them. There are wires that are correct for mobile and marine use and ordinary Romex is not one of them. It is also very stiff and can be difficult to work with.

Regarding the grounds issue,our trailers more than others must rely on ground wiring to insure complete and safe grounding as there is often no clear path to a common ground just thru the trailer metal. In fiberglass trailers there is just not a common bonding to the frame as there is in other rigs. Also having been around the Playpac,it seems to have less going there than most. Most trailer lighting and electrical issues seem to arise as a direct result of poor/improper grounding.

It is no more difficult or expensive to do it right but it can really be an expensive problem not to.

All of the wiring and hardware to do this are available in the area and I use a wholesale place in the Westport area and the prices are even cery good.

I am working on my trailers over the weekend and am always happy to help.

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Old 01-04-2008, 08:07 PM   #6
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You guys are so great. Thank you for the comments. I feel much better, knowing I'm on the right track.

Ed. I will give you a call this weekend. I haven't got the trailer back from Camper Exchange yet. They are doing the 120v work, as I really wasn't up to attempting that. I think I can figure out the 12 volt stuff tho'


Plotting my next adventures...
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Old 01-04-2008, 10:00 PM   #7
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I would be more inclined to use an ATC fuse-style block with the now-common automotive blades fuses, like maybe the one of the ones on this page.

I would be inclined to stay away from single-conductor house wiring simply because it is more difficult to work with on these DC terminals. If I want larger sized wires, I use house-hold multi-stranded cable.

BTW, there are 12VDC automotive/marine wiring cables make that not only have the stranded conductors but also have multiple, tough sheathing for protection, but it likely won't be found at Home Depot or NAPA.

Take a glance at the Scamp Owner's manual's wiring diagram for some typical RV wiring.

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