I have questions about wiring 12 volt LED light fixtures in fiberglass motorhome

[magentawave]

I'm rebuilding a Toyota Sunrader motorhome that I gutted and plan to live in and travel off the grid. The Sunrader is the motorhome with the fiberglass shell.

I plan on running 2 six volt batteries initially and probably expand to 4 later.

I need to run the wires for all the interior led light fixtures and have a few questions, please...

1) I already have a couple rolls of 14 gauge wire. Should I NOT use 14 gauge and buy 12 gauge wire instead?

2) Should I run ALL the wires in that black flex tubing (wire loom) everywhere - or just the areas where the wires go to the exterior of the vehicle?

3) Would you run the positive wire from each fixture to the battery so there's about 6 positive wires - or would you connect the hot wire from each light to a single positive wire that goes to the battery?

4) This is a fiberglass shell so the ground wire from the led light fixtures will have to ground to the steel frame. So I have the same question (sort of) as before... would you run each negative wire separately to ground to the frame - or would you connect each negative wire to a single main ground wire that would ground to the frame?

5) And IF its better to connect to a single main wire - how would you connect them? Use one of those "T" connectors or solder to the single main wire and wrap with electrical tape?

I'm a newbie at this stuff so thanks very much!

 

[javajoe79]

Personally I would run 1 long leg to power them all and T off of that leg to each light. Use bare butt crimps and cover with hear shrink. Use sealed heat shrink outside. Same process for ground. 14 seems sufficient for LEDs but I would go off of what they require power wise and choose the wire gauge accordingly. Use wire loom for all of it IMO

Another option is to run a heavier gauge up to junction blocks for power and ground, then power and ground each light off of the junction blocks.

 

[dwh]

I'm rebuilding a Toyota Sunrader motorhome that I gutted and plan to live in and travel off the grid. The Sunrader is the motorhome with the fiberglass shell.

I plan on running 2 six volt batteries initially and probably expand to 4 later.

I need to run the wires for all the interior led light fixtures and have a few questions, please...

1) I already have a couple rolls of 14 gauge wire. Should I NOT use 14 gauge and buy 12 gauge wire instead?

#14 is normally rated for 15 amps and you'll need a 15a fuse to protect it. You gonna have more than 15a of LEDs? If so, split it up into two circuits.

2) Should I run ALL the wires in that black flex tubing (wire loom) everywhere - or just the areas where the wires go to the exterior of the vehicle?

I wouldn't bother unless I was worried about abrasion chewing up the insulation.

3) Would you run the positive wire from each fixture to the battery so there's about 6 positive wires - or would you connect the hot wire from each light to a single positive wire that goes to the battery?

See answer #1. Run a pair, one positive, one negative. Tap off as needed to feed light fixtures.

Just like in a house.

4) This is a fiberglass shell so the ground wire from the led light fixtures will have to ground to the steel frame. So I have the same question (sort of) as before... would you run each negative wire separately to ground to the frame - or would you connect each negative wire to a single main ground wire that would ground to the frame?

Screw the frame. Just run the pos/neg pair back to the fusebox at the battery.

5) And IF its better to connect to a single main wire - how would you connect them? Use one of those "T" connectors or solder to the single main wire and wrap with electrical tape?

Quality crimp connectors mashed with a quality crimping tool, wrapped with heatshrink. Heatshrink is cheap and so is a heatgun. Anything else will eventually vibrate, loosen up and act goofy. Might take some years, but it'll happen.

And for Frick's sake, do the crimps properly:

I'm a newbie at this stuff so thanks very much!

FNG!

 

[Sabre]

I would really have a Google at some basic automotive or marine wiring how-to tutorials. You'll be miles ahead if you can avoid some of the common mistakes that well-intentioned folks make.

A couple of quick suggestions:

1. Run a heavier gauge wire pair (+ and - both) from the battery to a fuse block that's back in the motor home. Google a Blue Seas or similar fuse block to see what I mean. Run your circuits from this fuse block rather than all the way back to the battery.
2. Don't rely on the metal frame as a ground; use wire.
3. Connectors: forget wire wrapping and/or black electrician's tape. Do NOT connect wires that way you might in a home AC circuit. Get a decent crimping tool and crimp on ring connectors sized properly for the wire gauge. For end-to-end splices (or even taps into a run of wire), use Posi-Tap/Posi-Lock connectors or similar.

Spend some time reading through threads in the "Power Systems" subforum. There are a lot of good pictures and diagrams there, and a lot of knowledgeable suggestions that folks have made in guiding others.

 

[dwh]

1. Run a heavier gauge wire pair (+ and - both) from the battery to a fuse block that's back in the motor home.

I sort of doubt that he's gonna have two (later four) six volt batteries under the hood of his Toyota.

Do NOT connect wires that way you might in a home AC circuit.

I never said to use wirenuts and tape. I said use crimp connectors and heatshrink.

But the wiring *scheme* is exactly the same as a house. I.e., multiple fixtures, wired in parallel, fed by a single set of branch circuit feeder wires protected by a single fuse (or breaker).

 

[Nomad1]

Be Warned LED's are not the end all I have tried them over the last 5 years and have at least half fail and half of that start fires from overheating fuses be damned be aware of the fact that LED lights get hot very hot with some I have gone back to standered lighting just for peace of mind....

 

[Sabre]

...I never said to use wirenuts and tape. I said use crimp connectors and heatshrink....

No, you certainly didn't and I didn't direct my comments to you. His notion of wrapping wires together (even if soldered) sounds extremely naive. Vehicle wiring doesn't have to be complicated, but there are right ways and wrong ways to approach it. We've all seen some horrifying things out there. I bought a used Triumph motorcycle a number of years ago that had accessory lighting wired with regular household zip wire (lamp cord). The connections were just twisted together and taped, and the previous owner didn't know why the lights weren't working.

 

[javajoe79]

No, you certainly didn't and I didn't direct my comments to you. His notion of wrapping wires together (even if soldered) sounds extremely naive. Vehicle wiring doesn't have to be complicated, but there are right ways and wrong ways to approach it. We've all seen some horrifying things out there. I bought a used Triumph motorcycle a number of years ago that had accessory lighting wired with regular household zip wire (lamp cord). The connections were just twisted together and taped, and the previous owner didn't know why the lights weren't working.

I rebuilt an entire car once that had previously won a pro level race. It was a World Challenge Corvette. Many of the wire connections were twisted together, zip tied to lock the twist, then taped. It was hilarious going through that car. The guy who built it is still highly regarded in the Corvette community

 

[calicamper]

Quality led fixtures are a big deal. Lots of cheap chinese junk out there. 12volt basic leds run a low risk of fire. But any led with a step down transformer be wary of the quality.
Leds are polarity specific. I ended up using a neg bar for all the neg connections. Most led fixtures seem to be in the 1-1.5 amp draw so base your amp needs vs wire powering x number of lights etc.

Fuse every feed!
Its not to bad kinda fun to mess with actually. Quality fixtures might cost more but are worth it in the long run.

 

[IdaSHO]

Be Warned LED's are not the end all I have tried them over the last 5 years and have at least half fail and half of that start fires from overheating fuses be damned be aware of the fact that LED lights get hot very hot with some I have gone back to standered lighting just for peace of mind....

While I have never seen such a failure, I always over-wire and fuse for the load because of such possibilities.

Lighting in our custom camper is on 1amp fuses.


But again, never have I seen such a failure.

Nomad, the failures youve had, are they LED fixtures or LED bulbs in traditional fixtures?

 

[magentawave]

Thanks for the input everyone!

Besides the led interior lights described below, I will also have two or three DC plugins to charge my phone, ipod, ipad and run my Macbook Pro 17 laptop (and wiring for a DC fridge later too). For the 6 volt batteries, the plan is to have a steel bracket made that's welded to the frame behind the differential, similar to this: https://www.vanspecialties.com/gallery_van/yota-4x4/ Having said that I would have two to 4 6 volt batteries, there's an extra battery tray under the hood so I think I'll start with one 12 volt deep cycle battery there for now.

So here's a few more questions, please:

A) Someone asked if I would run more than 15 amps of LED lights. I'm not sure yet, but here's the information I found... Each led light fixture has two clusters of 21 tiny led's = 42 total and when you turn it on all 42 led lights go on. On the back of the fixture it says: DC 12 volt 2x2.3 watts 2x240Lm 3200K. Since there are two clusters of 21 leds in each light fixture, does "2x2.3 watts" mean that each fixture is actually 4.6 watts total?

B) I read somewhere that 12 watts = 1 amp. I doubt I would ever run more than two lights at one time, but let's say I had all six turned on (extremely unlikely!)... that means if each light is 2.3 watts then that would be 1.15 amps (2.3 watts x 6 lights = 13.8 watts divided by 12 watts = 1.15 amps). Correct? Or 2.3 amps if each light is 4.6 watts (4.6 watts x 6 lights = 27.6 watts divided by 12 watts = 2.3 amps). Correct? So whether each led light fixture is 2.3 watts or 4.6 watts, is 14 gauge wire still okay to run from each light to the positive and negative T's?

C) Based on the worst case scenario of each light being 4.6 watts with all 6 on at the same time (2.3 amps), what size should the fuse at the fuse block be? And does the size of the fuse change based on whether I use 12 gauge or 14 gauge wire?

D) Should the positive and negative T wires be heavier than 14 gauge? If so, what size?

E) If I solder the light wires and heat shrink them the T's, how do you protect the space where the heat shrink on the light fixture wire T's into the heat shrink on the main positive and negative wire?

Thanks again.

 

[dwh]

A) Right. 2 x 2.3= 4.6.

B) Provided the specs on the LEDs are correct, you are doing the math mostly right. But you have to account for volts.

Watts divided by amps equals volts
Watts divided by volts equals amps
Amps times volts equals watts

Now assume your battery is at full charge voltage of 12.8v. So...

6 x 4.6 watts = 27.6 watts
27.6 watts / 12.8 volts = 2.1 amps

But as your battery drains and voltage goes down, to feed the same watts, the amps goes up.

27.6 watts / 10.5 volts = 2.6 amps

C) The fuse is there to protect the wire by melting before the wire does. So to protect wire rated at 15a, you use a fuse rated at 15a. Doesn't matter if you have 2a of load on the wire or 15a, you use a 15a fuse. You could use use a smaller fuse, but there is no reason to.

D) If you are feeding 2a of load with wire rated for 15a, you are already way oversize on the wire. So no, you don't need heavier. Besides, it's poor practice to change wire size in the middle of a run. Use #14 wire - rated at 15a and protected by a 15a fuse - for the whole run, end to end, fusebox to fixture.

[Edit: Should have said, "fusebox to fixture, to the next fixture, and the next, etc."]

E) Don't solder. Use crimp-on plugs to connect the fixture wires to the #14 so you can unplug and replace the fixtures when they crap out, without having to monkey with the main wiring.

 

[dwh]

You will use parallel wiring...

(And will have a fusebox at the end, not a transformer.)

 

[javajoe79]

To answer E more specifically.....

It sounds like you are envisioning an actual T junction. What you actually do is cut the main wire, slide on a piece of heat shrink, strips both ends then crimp them back together along with another leg of wire to feed each light then slide the shrink wrap over the junction and shrink it. Some people like the self vulcanizing electrical tape. It works well for inside the camper but I prefer using heat shrink with the sealant inside for inside and outside use.

Here are the butt connectors

http://www.wiringproducts.com/22-10-gauge-non-insulated-butt-splices

here is the sealed heat shrink

http://www.wiringproducts.com/dual-wall-heat-shrink-with-adhesive

 

[javajoe79]

Dont forget the tried & true Vampire Connector.
They work well, otherwise the RV & trailer business would never use them in abundance.
You dont even need tools, just ********** them between a couple stones.

I hate those things but they do work