Wiring primer for newbie?

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Jan 29, 2007
I want to add electrical to my trailer.  Currently it has no lighting, etc. If I wanted to add 12v lighting, A/C, 120v outlets, an external port for either shore power or my generator to plug in, is there a primer for how to do all of this?  I am assuming I would need a couple 6v batteries in series, and an inverter?  I am not electrician, perhaps I need a pro.. Any guidance?

John From Detroit

Well-known member
Apr 12, 2005
Davison Michigan
120 volt wireing is the same as a house, There are several "Self help" books which you can get at Lowes, Home Depot, or many hardware stores which will assist you there.  There are very few differences in RV wiring.

1: You need some kind of "inlet" this may be a pre-wired cord with a plug on one end and just wires on the other end or it may be a special "inlet"  I suggest the cord, much cheaper.

2: NEVER,  and I mean NEVER bond the neutral to ground on a trailer unless you have no choice (this is common in house wiring) Neutral is the white wire, Ground is either green or bare wire.

12 volt wiring is very much like 120 volt wire only you tend to use less expensive wire (single insulated instead of romex) no reason you can not use romex for 12 volt save one.. I would hate to confuse the two wires later on.  Remember a single lamp on a 12 volt line can easily draw 1-2 amps (Equivlent of 100-200 watt 120 volt lamps) so use heavy enough wire

I also suggest a good power converter to charge your batteries.  Progressive Dynamic Intella-power with charge wizard is one of the best converter/chargers made.  NOTE: one of the best, not the only one, others are as good, none better.  This unit can run sensitive radios with the batteries disconnected (Don't forget a disconnect, I like the knife switch type)

And mine does not boil batteries dry either.

Batteries.  You want true DEEP CYCLE, not marine or starting batteries,  If you use flooded wet cells most folks have Golf Cart batteries (in pairs) these are six volts but six+six = twelve so it works  Treat each pair wired in series as one 12 volt battery.

Others use AGM batteries  The above listed converter is NOT the best for AGM batteries (It will over charge them and shorten their life)

Finally you need to decide if you want to run 120 volt stuff off batteries.. For example I run communications hardware (Sat-modem) and television stuff off a Xantrex Prosine 2.0  This unit is hooked to a bank of AGM batteries in my coach (Which are all used by it and nothing else) the Xantrex is a true sine wave (Very kind to the down stream hardware) I do suggest true sine wave.  IT also has a charger in it which can be set for AGM batteries, and is among the best for that type of battery.

Should you do this,  Neutral will be bonded to ground in your inverter and possibly your charger, This is not dangerous, it simply means you can not plug into a GFCI outlet at a camp ground.

Finally there are the distribution boxes (Breaker/Fuse boxes) for RV's Progressive Dynamics and others make good ones  at the 12 volt level the PD fuse panel has LED's to tell you which fuse is blown, Very nice.

At the 120 volt you can get 3 or 4 kinds of boxes.

1: 30 amp, no inverter
2: 30 amp with inverter
3: 50 amp no inverter
4: 50 amp with inverter

I would get the 50 amp panel even if you don't put in 50 amp service,  But then I'd put in 50 amp service too  The reason is you may wish to upgrade to 50 later

50 amp panels are 240 volt They have 2 main breakers and 2 power busses 30 amps are 120 volt.  All the stuff in your trailer is 120 volt but as with your house the 50 amp panel is 120-0-120  The "With inverter" option gives you an additional "Inverter" buss.  This makes it very easy to add the inverter.  If you don't get an inverter right away just leave this section of the panel empty.

Gary RV_Wizard

Site Team
Feb 2, 2005
At our Silver Springs FL home
John gave you a pretty good summary.

You don't need an inverter unless you want to be able to run 120VAC stuff without being plugged to shore power or running the generator.  You will need more batteries if you plan on using an inverter to any significant degree.

You need to make some kind of estimate of your power needs (intended usage) to figure out how many circuits and where to place them, a well as the total shore power and genset load. This will determine the generator size and shore power sizing (20 amp, 30 amp, 50 amp, etc).

If you haven't done any electrical work before this is a fairly complex first project. The self help books would get you through it, ut a friend with some expereince would be even more help!
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