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Old 10-07-2021, 09:12 AM   #1
Mini-Skoolie
 
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Duplex vs. single strand marine grade wiring

Quick question for the Skoolie brain trust. I'll be finishing the "deconstruction phase" soon and next phase will be framing & wiring. I see most people running single strand 12V wire, even with return to ground wire loops. The question is why? Wouldn't the same wire type/gauge in a duplex housing be way easier? Not to mention the protection the sheathing itself provides. Seems like a no brainer to me, but since I don't see other's using it there must be a reason. Enlighten me.

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Old 10-07-2021, 09:34 AM   #2
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Originally Posted by ddwbeagles View Post
Quick question for the Skoolie brain trust. I'll be finishing the "deconstruction phase" soon and next phase will be framing & wiring. I see most people running single strand 12V wire, even with return to ground wire loops. The question is why? Wouldn't the same wire type/gauge in a duplex housing be way easier? Not to mention the protection the sheathing itself provides. Seems like a no brainer to me, but since I don't see other's using it there must be a reason. Enlighten me.

Itís usually easy to find single conductor wire, I think thatís probably most of it. Certainly for me it was. I think dual conductor wire would make for a cleaner installation and work fine however. Could be cost related too.

14/2 romex like people use in houses (because itís solid core, single strand) probably shouldnít be used for DC and most of the other multi conductor wire that I find locally is small gauge stuff for sprinklers and things, or SJ or SO but I feel like that stuff is a lot more expensive (and takes up more space) than thhn that I used.

Best part of skoolie life is that you decide!
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Old 10-07-2021, 09:50 AM   #3
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Originally Posted by ddwbeagles View Post
Quick question for the Skoolie brain trust. I'll be finishing the "deconstruction phase" soon and next phase will be framing & wiring. I see most people running single strand 12V wire, even with return to ground wire loops. The question is why? Wouldn't the same wire type/gauge in a duplex housing be way easier? Not to mention the protection the sheathing itself provides. Seems like a no brainer to me, but since I don't see other's using it there must be a reason. Enlighten me.


(Duplex wire?)
Are you asking about tin & talcum coated two conductor wire for marine applications?
Expensive. No bare ground wire.

Provides what additional protection?

Whatever you choose should be inside of conduit OR approved to be secured free-air (exposed or concealed).
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Old 10-07-2021, 09:53 AM   #4
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Clarification. Single strand was a poor choice of wording. I should of said individual thhn stranded wires of each color verses that same wire (marine grade, thhn, in a duplex housing). It's actually cheaper per 1k' spool in that configuration. $.228 (x2 for red And black) p/ft individual wire vs. $. 38 for same wire in duplex sleeve. (14g prices listed BTW)
But you answered the question that there were no real drawbacks going that route.

Thanks
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Old 10-07-2021, 09:55 AM   #5
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DeMac - Yes, that is the style. No ground? It's a two wire set up right? Red is power lead, black is neutral or ground. You lost me there.

And good Lord the pic you posted is outrageously expensive!!!
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Old 10-07-2021, 10:23 AM   #6
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DeMac - Yes, that is the style. No ground? It's a two wire set up right? Red is power lead, black is neutral or ground. You lost me there.

And good Lord the pic you posted is outrageously expensive!!!

Two conductors, really. Copper, jacketed separately. No color requirement for conducting electricity. Two hots ok, too (switch-loop). Conduction, +/= requires only Copper. (Fe, AL, Ag, etc)

Only one Earth, however. So, one ground on this planet. Bare conductors ought to be used for grounding, only. Not conducting. (So, no bare grounding wire.)

12v, two conductors is perfect
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Old 10-07-2021, 10:28 AM   #7
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I bought two boxes of class 3 speaker wire. On is 14/2 and the other is 12/2. It's perfect for LED lighting. Black & red in a white plastic jacket. I use this stuff on 70 volt sou d systems and cl3 is OK to run in walls
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Old 10-07-2021, 12:09 PM   #8
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If I could do over, I'd use the sheathed duplex It would avoid having to fuss with conduit or worry about chafing.
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Old 10-07-2021, 12:39 PM   #9
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Do you mean romex? If not, I have no idea what duplex wire is. Is it just a fancy word for 2 stranded thhn wires in a jacket?

I used romex stranded 12/2 w/ground to wire up the air conditioner. It's ran in the walls without conduit next to the bus wires ran to the back.

I was told not to run solid wire, as the solid wire will have a greater chance of work hardening in a mobile environment, becoming brittle, and then breaking.
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Old 10-07-2021, 12:44 PM   #10
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Do you mean romex? If not, I have no idea what duplex wire is. Is it just a fancy word for 2 stranded thhn wires in a jacket?

I used romex stranded 12/2 w/ground to wire up the air conditioner. It's ran in the walls without conduit next to the bus wires ran to the back.

I was told not to run solid wire, as the solid wire will have a greater chance of work hardening in a mobile environment, becoming brittle, and then breaking.
Yes, I believe duplex the name for a sheathed, two wire conductor. Solid wire in homes, stranded in marine and mobile applications. I think Romex is a brand name, like Kleenex.
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Old 10-07-2021, 02:59 PM   #11
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Originally Posted by Booyah45828 View Post
Do you mean romex? If not, I have no idea what duplex wire is. Is it just a fancy word for 2 stranded thhn wires in a jacket?

I used romex stranded 12/2 w/ground to wire up the air conditioner. It's ran in the walls without conduit next to the bus wires ran to the back.

I was told not to run solid wire, as the solid wire will have a greater chance of work hardening in a mobile environment, becoming brittle, and then breaking.
I didn't know they made stranded romex. I use stranded M/C at work, 12-2 & 12-3 because it's easier to work with and I'm usually alone. I'm planning on using that on my bus
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Old 10-07-2021, 03:06 PM   #12
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As mentioned, I think the more frequent use of single conductor automotive primary wire is just that it's more easily available than 2-conductor jacketed automotive wire (GPT rated and such). I believe this to be because it's common in autos and RVs to use the chassis as a negative (usually) and to ground things locally, so you don't always need the second conductor unless you're doing home-run grounds. So, the GPT type wire is normally sold in single conductor rolls.

As far as 120V circuits go, the RVIA has approved "Romex" solid wire for quite a few years now and we've worked on old conversions with solid wire...and I've not seen any evidence of work hardening or failure in those.
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Old 10-07-2021, 06:40 PM   #13
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Marine rated UL1426 105C wire is the way to go, especially for any exposed to the elements

Pacer is an excellent brand and often cheaper than Ancor.

http://www.bestboatwire.com/custom-cables

is a good source
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Old 10-07-2021, 07:40 PM   #14
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This is the low voltage wire I mentioned. It comes in a variety of different sizes and is perfect for LED lighting and other 12 volt loads. With the ground included, you can use any dimmer and also not worry about some phantom ground screw somewhere in your ceiling coming loose. Driving lights, porch lights, diesel heaters....I'm a solder and shrink tube guy but good quality crimp connectors would be fine.


https://www.amazon.com/dp/B095187HLD...ing=UTF8&psc=1
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Old 10-07-2021, 08:50 PM   #15
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Pacer

Quote:
Originally Posted by john61ct View Post
Marine rated UL1426 105C wire is the way to go, especially for any exposed to the elements

Pacer is an excellent brand and often cheaper than Ancor.

http://www.bestboatwire.com/custom-cables

is a good source
Yes, I agree with John. Pacer (FL made, I believe) has good stuff, not speaker wire. It is rated for AC & DC, up to 600v. Nasty environments, sump pumps, diesel transfer, chicken poo... $0.85/ft (@250') the screenshot is from thier website. Idk, however, how thier factory direct retail compares to the resellers' prices.
https://www.pacergroup.net/duplex-cable-12-awg/
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Old 10-08-2021, 08:04 AM   #16
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I didn't know they made stranded romex. I use stranded M/C at work, 12-2 & 12-3 because it's easier to work with and I'm usually alone. I'm planning on using that on my bus
Couldn't tell ya where it came from. Was laying in the attic. I thought it was good at the time because it was 12/2 stranded and the ground was insulated vs bare like in normal romex. Probably not "romex" brand, but duplex wire, or is it triplex with the 3 wires?

Regardless, it doesn't matter, as it's been installed for over 5 years and isn't about to be removed.
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Old 10-08-2021, 08:05 AM   #17
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Originally Posted by rossvtaylor View Post
As far as 120V circuits go, the RVIA has approved "Romex" solid wire for quite a few years now and we've worked on old conversions with solid wire...and I've not seen any evidence of work hardening or failure in those.
Well that's good news I guess. Probably stick with the stranded as it's way easier to pull and lay, but it's nice to know solid wire won't fail in a mobile situation.
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Old 10-08-2021, 10:10 AM   #18
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Originally Posted by Booyah45828 View Post
Couldn't tell ya where it came from. Was laying in the attic. I thought it was good at the time because it was 12/2 stranded and the ground was insulated vs bare like in normal romex. Probably not "romex" brand, but duplex wire, or is it triplex with the 3 wires?

Regardless, it doesn't matter, as it's been installed for over 5 years and isn't about to be removed.
Probably just cable if some type. 3C 12AWG, the class rating is what's important. I probably would have used it too. The "speaker" wire I mentioned earlier has some people dismissing it on name alone. It's rated for 150 vac, at an amperage determined by gauge. Standard THHN is good to 600 volt. I'm using it for 12 vdc and in all honesty, it's overkill. Over on Facebook someone asked about torquing wire connections. I mentioned I have a torque screwdriver and only torque circuit breakers when the specs require it (main lugs entirely different). Now everybody with a 30 amp motor home is bying a torque screwdriver.
Common sense and the ability to think outside the box are key to these projects
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Old 10-08-2021, 11:29 AM   #19
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Don’t tell DeMac, but I used 12 gauge extension cord for my 12 volt wiring ;)
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Old 10-08-2021, 12:52 PM   #20
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Don’t tell DeMac, but I used 12 gauge extension cord for my 12 volt wiring ;)
Ha.

I know not.
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