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8ga wire...copper vs aluminum????


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I’m planning on using 25’ of #8ga wire to attach my remote , 120w/12v solar panel to my solar controller which is located at my battery box.

aluminum wire is lighter and less expensive. Any disadvantage to aluminum over copper? Any loss difference?

RoyB

South of Boston

2021 Dodge 2500 - 6.4L

Forest River 19RR Toy Hauler

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Aluminum has very good conductivity but less conductivity. You will find voltage loss charts for both copper and aluminum. Copper loses less voltage. It may not matter for you, but just look at the numbers and be aware. Also when you join aluminum and copper wires together it causes a chemical reaction and deterioration over time so use ox guard or similar product on any union.

 

Dave and Lana Hasper

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More care must be taken to install aluminum wire to avoid fire hazards. Intermittent heating and cooling from conduction cycles can cause connections to become loose with aluminum wire and possibly spark. Larger gauge aluminum wires are required to conduct the same loads as copper - so if space is a concern when routing, copper wins. 

Rob

2012 F350 CC LB DRW 6.7
2020 Solitude 310GK-R, MORryde IS, disc brakes, solar, DP windows
Full-time since 8/2015

 

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  rb, good question, here's my take:  I'm old enough to remember all the horror stories and fires caused by the improper or non maintained use of aluminum conductors way back in the day even though that was typically higher voltage and higher current residential applications. During my years as a power distribution engineer typically one place I saw it specified might have been from the Utility transformer to the service entrance (where properly installed by trained utility company professionals) but NEVER inside a home thereafter.

 Some of the reasons it was less favored by myself and other professionals was:

  It can be more brittle,,,,,,,,,, Typically less flexible,,,,,,,,,,,,Typically doesn't withstand frequent bending as well as fine copper,,,,,,,,,,,,,,,,Requires the use of anti oxidant in certain connectors,,,,,,,,,,,Some connectors are NOT approved for aluminum,,,,,,,May require more connection maintenance,,,,,,Being higher in resistance requires larger wire gauge for the same current,,,,,,,,,,,Doesn't mate well with dis similar metal such as copper (battery action and corrosion potential).

NOTE I'm NOT saying aluminum doesn't "work" and for sure its lighter, IM ONLY SAYING BASED ON MY TRAINING AND EXPERIENCE I WOULD NEVERRRRRRRRRRRRRRR use it in an RV application (even if any codes allowed it Yeah Right lol). I prefer fine stranded copper conductors as they are more flexible and can withstand RV road vibration and even Marine Grade if one chooses. However for the "good side"

PS in your earlier post where 8 Gauge wire was discussed, I was thinking Copper. If you were to use aluminum and 8 Gauge in copper was actually necessary ??? that would have to be increased BUT I STILL DONT LIKE IT for all the reasons cited above. FWIW USE FINE STRANDED COPPER IS MY ADVICE. On the "good side" however if the RV has an external plug and you're ONLY using aluminum for the exterior run from panel to the plug, its not near as hazardous or unsafe or as critical as all that I described above and sure would  "work" YOUR MONEY YOUR RV YOUR CHOICE      

Best wishes

John T  Long retired n rusty EE but still believe this to be true. Consult trained professionals where fire or life safety is an issue.

Edited by oldjohnt
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1 hour ago, rbertalotto said:

Thanks, I ordered 25’of pure copper welding wire #8.

but for my own edification.....how about copper coated aluminum stranded wire?

1) That 8 Gauge pure copper welding wire should work fine at the distance and current you're dealing with CONGRATULATIONS

2) I would prefer copper coated aluminum over aluminum only given the proper use and circumstances but it (aluminum core) can still have some (even if less) of the problems I spoke of above.

   John T  

  

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1 hour ago, rbertalotto said:

Thanks, I ordered 25’of pure copper welding wire #8.

but for my own edification.....how about copper coated aluminum stranded wire?

I find best price on welding cable  is at welding supplies. Just pickuped some #4 today for .885 per foot

2003 Teton Grand Freedom towed with 2006 Freightliner Century 120 across the beautiful USA welding pipe.https://photos.app.goo.gl/O32ZjgzSzgK7LAyt1

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I have found welding cable to have poorer quality insulation. I'm sure some are better than others. Marine grade seems to be consistently high quality, plus has tinned plated wire strands for corrosion protection. 50 feet of 8 awg is 42.50 with shipping at Genuine Dealz . com for a few $ more they will make to your length with proper crimped lugs. I would not use marine or welding cable exposed on roof.

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17 hours ago, rbertalotto said:

Thanks, I ordered 25’of pure copper welding wire #8.

but for my own edification.....how about copper coated aluminum stranded wire?

Most welding cable is no UL listed.  Without a UL there's no way of knowing what the % of copper is.  The UL must be printed on the wire. 

The UL for welding cable is UL1276 ....FYI...UL1276 welding cable is not NEC approved for fixed of portable applications

Tinned coated marine wire is UL1426.

Wire for the solar installations is UL4730

 

 

 

 

 

 

 

 

 

 

2011 Cameo 34SB3

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 What can make matters worse and maybe even more confusing is I've owned RV's for 49 years and in many (not saying all) typical cases if you go to an RV dealer to buy wire and start throwing UL terms and ratings and questions to them unfortunately you may get the "Deer in the Headlights" look LOL. 

    If I was using wire that was all outside and ran from a portable solar panel to a plug on the side/exterior of an RV, at the very MINIMUM (in addition to more specs where applicable) Id want it rated for outdoor use with suitable ultraviolet protection, fine stranded copper with good vibration resistance and flexibility with a good insulation and jacket, and, of course, sufficient ampacity so as to limit line voltage drop. I'm not familiar with all the UL or any NEC or RVIA or any other ratings or codes required for wire strictly OUTSIDE an RV from a solar panel to an external plug ?????????? The Solar providers can probably answer that better than an RV dealer. I've purchased my Solar equipment from Solar rather then RV suppliers as they seem to be more knowledgeable in that regard.  For sure rooftop solar panel wiring exposed to so much sunlight must be high quality and rated for ultraviolet !!!!   Id say such use (Outside wire from solar panel to external RV plug) would be different from pure RV INTERIOR  or Marine applications.

 Do your research and homework and consult trained professionals when selecting components and wiring DUH

 John T 

Edited by oldjohnt
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I had a set of jumpers made from welding cable. The insulation split and had to be repaired many times. I'm sure there are better grades of welding cable, but I don't know how to pick the better ones. All I'm saying is marine grade made in usa is the best choice for me. I do know that it will be the best quality. GDZ delivers in one or two days from ordering. Solar panel leads, with MC4 ends, is from Windy Nation solar supply.

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  FWIW Over many years I have experienced the same satisfaction as Glenn above when it comes to "welding cable". While a past used equipment dealer and farmer I came across a ton of welding cable and it generally speaking had good quality tough high abrasive resistant jacket/insulation as it got dragged down gravel or blacktop driveways up over and around all sorts of sharp steel or machinery and sharp bends plus often sat outside on a welding truck exposed to sun rain wind snow n drastic temperature changes grrrrrrrrrrrrrr it better be tough and good quality to withstand all that lol

 Of course, there are different grades and brands and quality, some maybe poor some maybe excellent, some cheap some expensive, but I may have lucked out as that which I came across happen to be great quality and endurability while some others may have  observed poor quality...….That comes as no surprise to me as there are a ton of manufacturers and grades out there.

 Unfortunately absent deep research I don't know how to tell what types or brands or specs or codes or ratings are good or bad for any specific application, so I wouldn't make any recommendations in the dark. DO YOUR HOMEWORK

 As far as any "Solar" wiring rating (UL or NEC or RVIA etc) a panel is a DC energy source such as a battery or charger etc etc so if a person were choosing so called  "Marine Grade"  or some sort of so called "Solar Grade" one thing I see as critical is the environment so if the wire is ran on an RV rooftop exposed to sun, rain and temp changes and regardless if the energy source were a charger or solar panel you need good ultraviolet protection as well as other element protection including flexibility and vibration resistance.

 Marine Grade, Solar Rated, Welding Cable, UL, NEC, RVIA, may all have a role in decision making. Do your research and make your choice that's best for YOU...……….

   Best wishes yall, very fun and interesting thread for us sparkies at least lol

 John T

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Ok, so marine grade cable makes sense in the environment our RVs are subjected to....

Most marine grade cable is tinned copper. It it really “tin” or is it solder?

does this coating have an negative effect as it pertains to voltage loss?

RoyB

South of Boston

2021 Dodge 2500 - 6.4L

Forest River 19RR Toy Hauler

Roofnest Falcon Rooftop Tent

www.rvbprecision.com

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15 minutes ago, noteven said:

Don’t the little electrons “flow” down the outside of the wire kinda? Therefore many strands are better for low voltage pressures? 

Or did I read false news somewhere?

Generally agreed upon. 

ETA: Also helps with flexibility. 

Edited by Darryl&Rita

I have been wrong before, I'll probably be wrong again. 

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1 hour ago, noteven said:

Don’t the little electrons “flow” down the outside of the wire kinda? Therefore many strands are better for low voltage pressures? 

Or did I read false news somewhere?

I believe that this is correct only for A/C current at high voltages. For our DC systems in the 12V - 48V range there is no so-called "skin effect".  However, lots of small wires does make for good flexibility, so there is that...

Mark & Teri

2021 Grand Designs Imagine 2500RL, 2019 Ford F-350

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Found this...

alternating current produces alternating magnetic flux inside and around the conductor. ... this effect is more at the center of conductor. so electrons tend to flow through surface. In DC there will not be any alternating magnetic field and so no Skin effect is not observed”

RoyB

South of Boston

2021 Dodge 2500 - 6.4L

Forest River 19RR Toy Hauler

Roofnest Falcon Rooftop Tent

www.rvbprecision.com

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  rb, as I best recall (NO Warranty) the so called "skin effect" was only of major concern when talking high frequency and NOT in DC circuits. You're only talking about a 25 ft DC run OUTSIDE an RV FROM a portable energy source TO an external Outlet/Plug (or other connection method) at (if 17 Vmp at 120 watts) 7 Amps DC max, so I think 40 Amp rated wire (such as #8 Copper or other 40 Amp rated equivalent) be it some sort of so called "Marine Grade",  be it some sort of so called "Solar Rated" or be it some sort of so called "Welding Cable" will  "WORK" satisfactory. NOTE, I'm NOT saying the grades or ratings or any UL or NEC or RVIA approved wire (to the extent any such exist or are even applicable) shouldn't be considered and its best to reduce line voltage drop as much as one can, I'm ONLY saying ANY of such conductors approved for exterior and wet locations with ultraviolet protection and 40 Amp rated is a decent choice and I wouldn't loose much sleep overthinking or worrying too much beyond that.

CONGRATULATIONS you ask good questions and are doing research so you should end up with a good product. 

John T

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