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Open Roads Forum  >  Tech Issues

 > What gauge wire do I use

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Sam Spade

North Central Florida

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Posted: 07/11/19 05:35am Link  |  Quote  |  Print  |  Notify Moderator

Campin LI wrote:

GordonThree wrote:

6/3 or heavier for the future.
Thanks. I was thinking 8, thinking 6 is a bit overkill. Why 6? Does 6 fit in a 30 amp breaker?


Good thought about the breaker.

You should be able to do a quick "test" for fit at the hardware store before you actually buy anything.

I was thinking that the "for the future" comment was aimed mostly at the very real possibility that you might "upgrade" your RV in the future to one that needs 50 amp service, which has two 120 V 50 amp legs, which would require a heavier wire.


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Chum lee

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Posted: 07/11/19 02:34pm Link  |  Quote  |  Print  |  Notify Moderator

I like to think of wire gauge like this. (from an engineers perspective)

With a 30 amp 120 volt circuit and a 200' run:

If you want the system to work reliably at least 80% of the time use 12 gauge copper wire. (chance of fire exists)

If you want the system to work reliably 90% of the time or more use 10 gauge copper wire. (chance of fire exists but is quite low)

If you want the system to work reliably 95% of the time or more use 8 gauge copper wire.

If you want the system to work reliably more than 99% of the time use 6 gauge copper wire.

If you want someone to come and steal your copper wire, use 4 gauge.

You don't get to decide when the system fails to work reliably. You do get to decide the chances of how reliable it will be if/when it works. It's kind of like the weather. Even if there is a 100% chance of rain, . . . it's still just a chance.

Chum lee

DFord

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Posted: 07/11/19 02:49pm Link  |  Quote  |  Print  |  Notify Moderator

Chum lee wrote:

I like to think of wire gauge like this. (from an engineers perspective)

With a 30 amp 120 volt circuit and a 200' run:

If you want the system to work reliably at least 80% of the time use 12 gauge copper wire. (chance of fire exists)

If you want the system to work reliably 90% of the time or more use 10 gauge copper wire. (chance of fire exists but is quite low)

If you want the system to work reliably 95% of the time or more use 8 gauge copper wire.

If you want the system to work reliably more than 99% of the time use 6 gauge copper wire.

If you want someone to come and steal your copper wire, use 4 gauge.

You don't get to decide when the system fails to work reliably. You do get to decide the chances of how reliable it will be if/when it works. It's kind of like the weather. Even if there is a 100% chance of rain, . . . it's still just a chance.

Chum lee


What are the odds for failure over an extended period? Say it's a hot day and A/C runs all day putting a heavy load on those wires. The heat builds up over time as the load increases and the chance of a failure do also. Using the proper size wire minimizes that risk potential. Where's the economy if you install a wire that's too small and burns up, then need to do the whole job over again with a larger size wire?


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MEXICOWANDERER

las peƱas, michoacan, mexico

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Posted: 07/11/19 03:06pm Link  |  Quote  |  Print  |  Notify Moderator

If you want CHEAPER use COPPER PLATED aluminum wire and SOLDER the terminals. Avoid NoOx chemicals and prep with D100 antioxidant cleaner then smear with silicone grease.

"Ah bah off-spec gaso-leen twenty fahv cents a gallon cheapah. So what is an occasional hoal in a piston?"

Replace a roof air and a couple of converters. Focus on the hundred dollars or so you saved when you bought the wyah. Redneck logic.

Ah caint be overdran Ah still got check left, logic.

Mr. Chum Lee, take a gander at a high head pressure re-start with even 200' eight gauge wire. What is your voltage? It'll have you squeezing your buns tighter than you'd ever expect.

Gotta nearby oak tree branch and a come-along you can drive out from under?

Electricity is mean it has no sense of kindness.

Boomerweps

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Posted: 07/11/19 08:38pm Link  |  Quote  |  Print  |  Notify Moderator

I ran 12AWG about 195' from the circuit breaker box to the TT. With just the Air Conditioner running and D.C. Converter, voltage was 103.7. 112.5 at the TT inlet without the AC on. At house, voltage was 125vac. Forget 12AWG supplying several TT items at the same time.
Parked at another place at home, 90' of 12AWG with AC & converter only, voltage dropped to 107.7.
All measured using a Kill-a-watt meter.
In your case, go with 6awg if you can afford it. 8awg minimum. Actually, strongly consider a closer storage site to the power source. Less voltage drop, shorter length of wire making thicker gauges more affordable.


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JimK-NY

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Posted: 07/11/19 09:26pm Link  |  Quote  |  Print  |  Notify Moderator

This is not rocket science. Any wire gauge calculator will answer the question. For a 30 amp circuit 200 feet you will need 6 gauge to maintain 5% or less voltage drop.

Cummins12V98

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Posted: 07/12/19 08:24am Link  |  Quote  |  Print  |  Notify Moderator

GordonThree wrote:

6/3 or heavier for the future.


Future what? If going that size there needs to be 4 wires to go 50A 240V. If so 6/3-8/1 or 6/4 will get you 50A.

For that distance and ONLY 30A I would run 3 wire #8, shorter distance #10 is fine.


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Cummins12V98

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Posted: 07/12/19 08:27am Link  |  Quote  |  Print  |  Notify Moderator

"If you want someone to come and steal your copper wire, use 4 gauge."

I think he mentioned underground wire.

Chum lee

Albuquerque, NM

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Posted: 07/12/19 12:10pm Link  |  Quote  |  Print  |  Notify Moderator

DFord wrote:

Chum lee wrote:

I like to think of wire gauge like this. (from an engineers perspective)

With a 30 amp 120 volt circuit and a 200' run:

If you want the system to work reliably at least 80% of the time use 12 gauge copper wire. (chance of fire exists)

If you want the system to work reliably 90% of the time or more use 10 gauge copper wire. (chance of fire exists but is quite low)

If you want the system to work reliably 95% of the time or more use 8 gauge copper wire.

If you want the system to work reliably more than 99% of the time use 6 gauge copper wire.

If you want someone to come and steal your copper wire, use 4 gauge.

You don't get to decide when the system fails to work reliably. You do get to decide the chances of how reliable it will be if/when it works. It's kind of like the weather. Even if there is a 100% chance of rain, . . . it's still just a chance.

Chum lee


What are the odds for failure over an extended period? Say it's a hot day and A/C runs all day putting a heavy load on those wires. The heat builds up over time as the load increases and the chance of a failure do also. Using the proper size wire minimizes that risk potential. Where's the economy if you install a wire that's too small and burns up, then need to do the whole job over again with a larger size wire?


That's EXACTLY my point. How reliable do you want your system to be? Odds are just odds. In this example, nobody can predict how an individual user will load the system.

To the OP's question, MY answer is:

"If you want the system to work reliably more than 99% of the time use 6 gauge copper wire.

Whatever bean counter rational anybody decides to use is up to them. If you like fires and damaged equipment, then ignore the codes and go with 12 gauge wire. Don't like fires? Then spend some money on wire and buy some safety factor. How much safety factor do you want? That's up to you and your budget. It's not that hard. Do you feel lucky?

MEX: This is my advice for a very general example. In any case where SPECIFIC DEDICATED LOADS are well defined, the above WOULD NOT necessarily be my advice.

Chum lee

Chum lee

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Posted: 07/12/19 12:31pm Link  |  Quote  |  Print  |  Notify Moderator

Cummins12V98 wrote:

"If you want someone to come and steal your copper wire, use 4 gauge."

I think he mentioned underground wire.


You need to get out more. At $2.30/lb. (currently), 3 - #4 copper wires add up fast. (a rhetorical question) What makes you think that if something is buried in conduit, (even directly) it's safe from theft? It happens all the time, nice long runs make it even more appealing.

Chum lee

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