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Old 02-11-2016, 09:24 PM   #1
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Opelika , Alabama
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Newbie to RV power setup

I'm familiar with 120v power in homes and offices. I'm familiar with circuit breakers and load calculations and even with manual switches to switch from power company power to generator power. But with an RV and 12V, I don't know how it's supposed to be setup. There seems to be a mix of AC and DC appliances. How should I begin thinking about this? Will all power come from my batteries, whether it's straight 12V or inverted to AC? Does 12V come from the batteries and AC from shoreline?

I'm gutting my Airstream 34 footer and rewiring it and I just need a little guidance on how I should go about thinking about power.


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Old 02-11-2016, 10:03 PM   #2
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The 12V Side of Life is a great intro to RV systems and devices. It's basic but a good foundation. There's a part II also.

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Old 02-11-2016, 11:04 PM   #3
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2015 28' International
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I've been learning the basics of my 2015 system and this is my understanding.

When you're on 120v shore power your ac comes from shore power and your 12v dv comes from the converter which is also charging your batteries.

When you're on batteries your 12v comes from the batteries and your ac comes from the inverter. The inverter does not power all ac plugs in the AS - the receptacles are separate from the ones that run on shore power and fewer in number.

The AS manuals online have both 12v and 120v wiring diagrams.
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Old 02-12-2016, 05:56 AM   #4
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Think of the trailer wiring as three separate systems, AC, DC, and Umbilical cord items.

Starting with the U-cord. All items on that are powered by the tow vehicle, except that the line that is intended to charge the trailer batteries from TV power while on the road can supply 12 v. power. It's not much different than the system you'd have on a utility trailer.

The trailer is wired so that you can camp with no exterior source of power, for a while, using only the onboard batteries. The DC system, with associated fuse panel makes that possible. You'll find lights, fans, furnace, etc. on this system. As I said above, the trailer batteries receive a charge from the TV's alternator when towing. This is usually insufficient to really keep the batteries charged. The primary source of battery charging is from a transformer/rectifier, called a converter, that is powered from the trailer's AC wiring. The converter also provides power to the DC lights and appliances while AC power is connected.

The AC system is usually a 30 amp 120 v. "house current" type. Some larger trailers are wired with a 50 amp system that gets 120 v. power from both legs of the power company's line. (There is a difference in wiring the neutral at the panel that someone more knowledgable than I should explain.) This system powers the converter as well as heavier loads that would be impractical on battery power. With AC power connected, you get air conditioning, microwave oven (although maybe not both at the same time) and outlets to plug in television sets, hair dryers, whatever. Load management is necessary to stay within the amperage available.

Some trailers have an inverter installed that will enable the use of small AC appliances when the trailer is not connected to shore power, for those who just cannot live without television.

Best of luck with your trailer. I hope this rough overview has helped.
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Old 02-12-2016, 07:29 AM   #5
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when you say rewire what are you intending to change? There aren't many reasons to rewire a trailer unless external damage, nice or fire, have happened.

You may be adding something, more lights or additional ac outlet for something new a second air conditioner, but that addition should not warrant "rewiring" only additional wiring
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Old 02-12-2016, 08:01 AM   #6
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If you are adding significant solar, larger battery bank and 2000+ watt inverter/charger, then yes, "extensive rewiring" will allow you to energize your entire trailer when off-grid.

With the new lithium/hybrid inverter technology, you can also run a roof A/C strictly from the battery-inverter combination or all day with a single 2000 watt generator. 😄

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Old 02-12-2016, 01:36 PM   #7
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Yes, it can be confusing. I'd recommend you find and attend an RV Boot Camp. The Escapees RV Club runs an EXCELLENT Boot Camp (others groups offer Boot Camps too). With the Escapees, you and about 200 other "newbies" will, over a weekend, learn about ALL the systems found on a modern RV. Mistakes made with RVs are often expensive and, sometimes dangerous. After completing RV Boot Camp, you will be a safer, more knowledgeable RVer. You can attend a Boot Camp even if you don't yet have an RV. Doing so will help make you a smarter RV buyer.
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Old 02-12-2016, 06:23 PM   #8
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The AC system is usually a 30 amp 120 v. "house current" type. Some larger trailers are wired with a 50 amp system that gets 120 v. power from both legs of the power company's line. (There is a difference in wiring the neutral at the panel that someone more knowledgable than I should explain.)

I think MIMIANDREWS is talking about 220 volts AC. The current in AMPS is related to the SIZE of the wire (gauge). The voltage is a function of 1 leg of the supply from the power company (black wire in HOUSE wiring) and neutral (white wire in house wiring) to get 110VAC. To get 220 VAC then BOTH legs of the supply (110VAC + 110VAC) added together gets you to 220VAC.

To up the size of a circuit breaker or fuses (CURRENT limiting devices) then the wire size would need to be upped (SMALLER guage number) to accommodate the extra amperage.

Hopefully I am not stepping on anyones toes, but I wanted to be sure everyone was clear on the voltage/amps stuff. BTW, the amps vs wire gauge holds true for 12vdc also. More current (larger fuse) bigger wire.
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Old 02-12-2016, 08:00 PM   #9
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Newbie to RV power setup

12 volt stuff is 12 volt, 120 volt stuff is 120 volt.

Your trailer uses a converter/charger to make 120 volt into 12 volt with your battery wired in a the circuit in parallel.

Trailers also use inverters to make 12 volt to 120 volt, but your trailer would not have had an inverter in stock form.

Brevi tempore!

The fact that I am opinionated does not presuppose that I am wrong......

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