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Old 02-05-2024, 09:50 AM   #1
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See this question a lot.

Seems like every thread I see involving PV charging or inverter chargers the question of wire size comes up.

Being a marine engineer for most of my adult life I would like to encourage everyone to actually do the math in this. Wire size matters! Electrical faults are the number one cause of fires and it needs to be respected and wire sizing is a top overlooked failure point.

I have attached a link for your reading pleasure. This article relates to marine applications but the rules and guidance are the same.

https://www.bluesea.com/support/articles/Circuit_Protection/1437/Part_1%3A_Choosing_the_Correct_Wire_Size_for_a_DC_ Circuit

One last note. Never use solid wire like Romex in a mobile application. It will weaken and break over time from flexing from road vibration. Use fine stranded wire that is designed for the job.

Thanks for reading
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Old 02-05-2024, 10:01 AM   #2
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Thank you for your contribution to educating the forum on electrical matters. It seems electrical discussions is where the most misinformation appears in this forum. Too many people think they understand electricity but they don’t, and their suggestions can lead to dangerous situations.
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Old 02-05-2024, 03:46 PM   #3
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One last note. Never use solid wire like Romex in a mobile application. It will weaken and break over time from flexing from road vibration. Use fine stranded wire that is designed for the job.
Thanks for reading
So does this mean I should replace the factory installed yellow Romex running rampant throughout my motorhome 15 years ago?
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Old 02-05-2024, 05:26 PM   #4
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So does this mean I should replace the factory installed yellow Romex running rampant throughout my motorhome 15 years ago?

Good point. Standard factory installed 120 volt wiring in my motorhome is all solid conductor copper.
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Old 02-05-2024, 07:04 PM   #5
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Quote:
Originally Posted by bubbles View Post
So does this mean I should replace the factory installed yellow Romex running rampant throughout my motorhome 15 years ago?
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Originally Posted by BehindBars View Post
Good point. Standard factory installed 120 volt wiring in my motorhome is all solid conductor copper.
Not only motorhomes, my 2022 5th wheel has plenty throughout as did all our previous R/Vs.
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Old 02-05-2024, 07:22 PM   #6
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AC solid 120v wire .... won't arc as bad if it broke.
higher voltage 120v = less amps needed...
modern wire insulation and switches etc can easily deal with 120v arcs



Crappy extension cords ... often abused and mishandled are the real culprits in the AC world ......... keep them in good condition and away from water.

-----------------------------------------------------------------------

Modern DC high loads @12v for inverters or large battery banks
can be hard to extinguish the arc once it gets started... hence the need for bulky switches and breakers.



don't try the two wires on the tongue test saying.... "It's just 12v"
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Old 02-05-2024, 07:42 PM   #7
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Not only motorhomes, my 2022 5th wheel has plenty throughout as did all our previous R/Vs.
I digress. The Rv industry is about “20 years behind the marine industry which is 10 years behind the automotive industry and the Rv industry has no real published standards

This pulled from the standard electrical code.

Poor flexibility: While solid wire is less expensive to manufacture than stranded wire, it cannot be used in environments where the cable has to be flexed. The conductor and insulation will break if they are repeatedly moved.

The Rv industry will do anything to save a dime. If you have a choice, which you do, choose fine stranded wire.
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Old 02-05-2024, 07:58 PM   #8
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I digress. The Rv industry is about “20 years behind the marine industry which is 10 years behind the automotive industry and the Rv industry has no real published standards
This pulled from the standard electrical code.
Poor flexibility: While solid wire is less expensive to manufacture than stranded wire, it cannot be used in environments where the cable has to be flexed. The conductor and insulation will break if they are repeatedly moved.
The Rv industry will do anything to save a dime. If you have a choice, which you do, choose fine stranded wire.
I think your use of the terminology "mobile application" period is misleading. Mobile applications where flexing will take place is surely to cause issues but in motorhome's and such flexing of Romex wire typically does not take place. At least in my motorhome.
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