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Old 02-27-2011, 12:12 PM   #1
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Recommended 110V Wire Gauge

Ready to install 30A Marinco type power inlet and am not sure of which gauge of wire to use from the inlet to the breaker. Have planned on the yellow 12 ga Romex from breaker to AC, fridge, micro, water heater, outlets, etc. Is 12 OK or should it be 10 ga as the power cord is?
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Old 02-27-2011, 12:16 PM   #2
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Ready to install 30A Marinco type power inlet and am not sure of which gauge of wire to use from the inlet to the breaker. Have planned on the yellow 12 ga Romex from breaker to AC, fridge, micro, water heater, outlets, etc. Is 12 OK or should it be 10 ga as the power cord is?
When in doubt, using the larger sized wire, is always the best choice. It costs a few cwnt more, but if you consider what you would have to do, to replace it, then that few cents, becomes next to nothing.

If you really want to make sure, use 8 gauge. Hurts nothing.

Andy 11.1k
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Old 02-27-2011, 12:21 PM   #3
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I used 10 G from the outlet to the breaker box. I believe that 10 G is necessary for the 30A circuit. I used 12 G everywhere else in the Liner.

Bill

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Ready to install 30A Marinco type power inlet and am not sure of which gauge of wire to use from the inlet to the breaker. Have planned on the yellow 12 ga Romex from breaker to AC, fridge, micro, water heater, outlets, etc. Is 12 OK or should it be 10 ga as the power cord is?
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Old 02-27-2011, 12:26 PM   #4
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Thanks Bill,

Guess I'll head out to get some more wire, I already had the 12 gauge.

Michael
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Old 02-27-2011, 01:32 PM   #5
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Andy,

I agree.

Thanks
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Old 02-27-2011, 01:50 PM   #6
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The smaller the wire size number, the smaller the voltage drop over a given length of wire ---- and this especially important when you are using 12v D.C. as in a trailer. I x R = Voltage Drop, so ---- the smaller the R, the better off you are.
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Old 02-27-2011, 03:10 PM   #7
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For 110 VAC copper wiring:

10 gauge minimum for 30 amp.
12 gauge minimum for 20 amp.
14 gauge minimum for 15 amp.

Standard building code / rv code stuff.

Chris
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Old 02-28-2011, 12:29 PM   #8
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Ready to install 30A Marinco type power inlet and am not sure of which gauge of wire to use from the inlet to the breaker. Have planned on the yellow 12 ga Romex from breaker to AC, fridge, micro, water heater, outlets, etc. Is 12 OK or should it be 10 ga as the power cord is?
Posters upthread are correct that 10 gauge is the minimum gauge, by code.

Depending on the distance from the breaker box to the outlet, you may need a larger size to avoid excessive voltage drop. The NEC says you're supposed to use large enough wire to keep the voltage drop to 1% at the actual current drawn by the load, which is pretty conservative. By their rules you're limited to a 20' run from the breaker box to the outlet at 10 gauge, around 30' at 8 gauge, and 50' at 6 gauge. (all based on 24 amps which is supposed to be the maximum design load for a 30 amp circuit). But in practice people don't use such large wire sizes, and you can maybe triple those distances before the voltage drop starts to get out of hand. In most campgrounds in the real world we see 10% voltage drop routinely when everyone is running their air conditioner.
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Old 02-28-2011, 12:35 PM   #9
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buy nice not twice

silverhoot--i did the same thing with the marinco outlet and went with the 30 amp compatible wire to my converter. then i used the same wire to run through the walls up to my 12 volt vent fan--just in case whoever inherits the trailer may want to put in ac a long time from now. bigger is better--just harder to work with. But it's nice knowing your wire's not going to fry. do it once. cheers ted
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Old 02-28-2011, 09:57 PM   #10
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Exactly right. 30 amp = 10 gauge wire, 20 amp = 12 gauge wire, 15 amp = 14 gauge wire by National Electric Code. To prevent insulation from melting off during overloads or short circuits, breakers must be sized per wire they protect. 30 amp breaker = 10 gauge wire, 20 amp breaker = 12 gauge wire, 15 amp breaker = 14 gauge wire. Insulation melting off the electrical condutor is the primary cause of electrical fires. That is the whole reason for properly sizing wire and breakers, to prevent fire!
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Old 02-28-2011, 10:04 PM   #11
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silverhoot--i did the same thing with the marinco outlet and went with the 30 amp compatible wire to my converter. then i used the same wire to run through the walls up to my 12 volt vent fan--just in case whoever inherits the trailer may want to put in ac a long time from now. bigger is better--just harder to work with. But it's nice knowing your wire's not going to fry. do it once. cheers ted
And by the way.............

If you want to do a really PRO job.......... throw away the solid core Romex and use 105*C stranded marine cable. Much easier to work with and will not have a chance to work harden and potentially break from road vibrations!

I NEVER use solid copper in any RV electrical or solar installation or repair. When the wire gauge gets above 8AWG, I use Grade K welding cable. More expensive....YES.........but oh so supple and easy to route around corners and into junction boxes.................and rated to 225*F to boot!!!
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Old 02-28-2011, 10:18 PM   #12
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And by the way.............

If you want to do a really PRO job.......... throw away the solid core Romex and use 105*C stranded marine cable. Much easier to work with and will not have a chance to work harden and potentially break from road vibrations!

I NEVER use solid copper in any RV electrical or solar installation or repair. When the wire gauge gets above 8AWG, I use Grade K welding cable. More expensive....YES.........but oh so supple and easy to route around corners and into junction boxes.................and rated to 225*F to boot!!!

This is some good information. You had me at supple......
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Old 02-28-2011, 10:23 PM   #13
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This is some good information. You had me at supple......
Remember, this is a G-RATED site!!
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Old 02-28-2011, 10:42 PM   #14
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GREAT info!

Quote:
Originally Posted by lewster View Post
And by the way.............

If you want to do a really PRO job.......... throw away the solid core Romex and use 105*C stranded marine cable. Much easier to work with and will not have a chance to work harden and potentially break from road vibrations!

I NEVER use solid copper in any RV electrical or solar installation or repair. When the wire gauge gets above 8AWG, I use Grade K welding cable. More expensive....YES.........but oh so supple and easy to route around corners and into junction boxes.................and rated to 225*F to boot!!!

Thanks Lewster, I used marine grade for all trailer to tow vehicle hookup, basically all my 12V wire will be marine grade stranded but already have the Romex so will probably use that for the 110v. What I removed was aluminum and it still worked.
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