Wiring cargo trailer conversion for 110 volts

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byrd

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Sep 13, 2017
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I am converting a 7X116 cargo trailer to a camper and want to wire it for 110 volts, where can I get some insight?
 
If you could find a rv salvage yard or an old camper that has been water damaged badly, you might be able to score the disconnect, cord, panel ect out of it. Possibly the fridge and furnace as well. Do you plan on having electric power only, or a mix of 12 volt. I would suggest some 12 volt led lights for sure even if you have regular a\c lights. The fridge and furnace if you are having one, will need 12 volt unless they are the very old style that you have to light manually. Being 116 ft long might create some driving problems lol.
 
Insight? Wire it just like an RV. If running a generator plug shore cord into genny or bolt genny down and add a transfer switch. If your generator is remote start it's even nicer and you both stay inside instead of forcing DW to go out and start it all the time.
 
Sorry about the typo, it's 16' not 116, LOL.  I should have explained a little better.  I want mostly all 110V, I do have a couple of 12V LED's planned and will install a small inverter/charging unit, which I have to I have not done yet.  This trailer has avery small 12V battery hooked into the trailer wiring to run the two led's, but I need to upgrade to a larger battery and a small charging unit.  I am using a Mr. Heater propane unit for my heat and an on demand propane water heater.  My other appliances are common 110V.  My concern is that I am wired safely and properly to use Service connects at RV Parks.  I'm installing a small breaker panel with two 15A circuits and two 20A circuits, 10gauge service coming in wired for 30A main 110V.
 
Sounds like you're doing it right, but make your electrical panel a little larger and install a 30 amp main breaker, not just the branch circuits. You don't want to rely on the park's breaker interrupting the power, especially if you use an adapter to plug into a 50 amp outlet.

The main breaker can be on the same row as the branch circuits, it doesn't have to be separate.  Just connect the hot side of the shore power cord to the terminal on the breaker, so power flows through it to the other breakers.

Your panel also needs separate ground and neutral busses, as they are not bonded (connected together) in an RV panel.

One clarification, though.  Combination inverter/chargers are usually available only in large, whole house units.  For what you describe, you want a converter that changes 120 volt shore or generator power to 12 volts DC, then a separate inverter to change the 12 volt battery power to 120 volts AC.

For a converter, look at the Progressive Dynamics 9100/9200 series.

The inverter can be anything from an inexpensive ($30 - 50) modified sine wave inverter on up to a whole house sized unit.

Small pure sine wave inverters are coming down in price, these will avoid the hums and buzzes you sometimes get from modified sine wave power.

There are a couple of ways to wire an inverter.  One is to make it large enough to power the entire trailer, and either install a transfer switch ahead of the electrical panel to select either shore or inverter power, or simply plug the trailer's electrical cord into the inverter when you're not connected to shore power. 

Usually the shore power cord is hard wired to the electrical panel and has a small compartment with a 4"x4" entry door where it is stored.  You stuff the cord into the compartment, if you mount an electrical outlet in there connected to the inverter you just plug the shore power cord into it and you have inverter power throughout the trailer.  Just make sure the inverter power doesn't feed the converter or you'll create a power wasting loop where one device is turning 120 volts into 12 volts while the other is doing the opposite.

Another option is to connect some outlets just to the inverter.  This means the inverter has to be on whenever you want to use the outlets, but the converter/charger makes up for that drain when you're plugged into electricity.  This has the advantage of creating a UPS, filtering out AC dropouts and surges from the inverter outlets.
 
QZ said:
Dont bond it.

In case you don't know what he means, is don't attach the neutral bar to ground. You must keep that neutral bar from touching the box, assuming the box is metal, and don't install the green bonding screw. You must use a separate ground bar, and you can't mix neutrals and grounds on those bars.
 
Make sure you read paragraph 567.7.

https://www.gpo.gov/fdsys/pkg/CFR-2011-title49-vol6/xml/CFR-2011-title49-vol6-part567.xml
 
Forum Staff,
Thanks for the insight!  I am trying to make this as simple, safe and inexpensive as possible.  I have already roughed in a breaker panel without a main.  I guess I'll just go get a 30A disconnect and use it for the main.  I don't want to be elaborate at all with any 12V supply.  I just wanted to wire this thing up basic so that if I'm at a park or friends house, whatever I can power some appliances and lights.  I have a full size solar generator to use when I'm not around any live power, (large enough for appliances, etc.) I'm not a rookie but I'm not well versed in inverters/chargers, so maybe I need to just skip it for simplicity and cost.  As you can probably tell I'm searching for some more answers.  Is there anywhere I could get a basic wiring diagram or some kind of a layout.  I'm perfectly willing to pay for advice I just don't know where to solicit the advice.  I will continue to use this trailer for work purposes as well as camping, I'm just kind of trying to figure out how to pull it all together.  I already have all of my lighting and basic recepticals wired in with 14gauge back to the breaker panel and I have wired in 2 20A circuits for microwave, AC and anything that would draw more current with 12Gauge wire back to the breaker panel.

Thanks to the retired Navy Aircraft Mechanic for that insight also.  I'm an "Old Salt" too, CVA 67, USS John F. Kennedy, Aviation Electronics Tech, 70 to 74.  Is there anything else I should be aware of for conversion requirements with regard to the Dept. of Transport?

Jay H.
 
Your expectations for what you can run on external power seem unrealistic. If at "a friend's house", you are probably plugging to a 15A/120v or maybe 20A/120v outlet, and modest campsites are likely to be either 15A or 30A @ 120v. 50A/240v campsites are typically the larger and pricier ones and found in more upscale parks. Not sure what your plans are for the RV, though.

You mentioned a 30A supply for a water heater alone. The water heaters in RVs are usually propane/electric combos and when on electric only they draw 1440 watts (12.5A). A 30A water heater sounds like a residential unit and may even be 30A/240v. An RV a/c unit draws another 1400 or so watts, and microwaves are in the same ball park, depending on size. You need to step back and think about how many appliances and convenience circuits you will have and which runs need to be able to run simultaneously. Then develop a power plan to provide that. I suspect you will find it is quite limited unless you plan for 50A/240v service, but that rules out most friends houses and the more casual RV campsites.
 
Gary,
Thanks for the reply!  I may have mistakenly said, "electric" water heater but I'm actually using an on demand propane heater.  I'm being realistic with myself on power usage.  In other words I know that a typical plug in at a friends or camp site will require me to be cautious about how many items I energize at once, my main draw will be a microwave or a self contained room AC unit.  I think most 30A hook ups will handle those ok.  I have some low wattage florecent light fixtures and a small fridge everything else is propane.  Just trying to get insight from folks like yourself to be as practical and thorough as possible.

Jay H.
 
If you are having a water heater, I am assuming you have a water tank and therefore a pump of some type. A 12 volt rv pump would be the most practical. I have a residential on demand propane water heater in my house, and it requires 120 volts to operate the exhaust fan. Im no expert, but I think it requires a certain flow rate before it will kick on. Im not sure if a 12 volt pump would provide the proper flow rate. Maybe it will. In my mind, your best bet is to wire it just like an rv, with several batteries that run 12 volt lights, an rv combo fridge, and a rv combo water heater. Might as well throw in the rv furnace. lol. Thats why I suggested finding a wrecked trailer. Lots of them around. Might save money salvaging all the parts you need. The older units have furnaces, water heaters,and fridges that you have to light manually, but dont require any 12 volt to operate. Otherwise, just wire up a panel, and run plugs like a house. You will only be able to operate if plugged into 120 volts, but maybe thats all you want. Good luck on your project.
 
I do agre 116 feet is a tad long are you sure you meant to type that (You would need permits to move it).

Now, to answer your questions:
Two ways you can wire a trailer  120 volt only for RV's is a 30 amp box. You can get one at any RV dealer. this is a SUB PANEL with a main breaker (most sub panels do not use main breakers but.. Thaqt said they are optional even on standard sub panels

White wire to the white bus. Green/Bare to the Green/Bare bus.. NOTE The two bus bars are NOT connected as they are in a MAIN box. that is the major difference between a SUB/RV panel and a MAIN panel.. White to the MAIN (master) Circuit breaker.  Limited number of branch breakers on a 30 amp box.

Or you can wire it for 50 amp 240 volt and on a trailer that big.. RECOMMENDED>

Different sub panel. you have either 2 blacks or a black and red. .White same as above, Green likewise, black or black and red one to EACH of the TWO main breakers..

Otherwise you are wiring a house. same as a house,  Just the breaker box is different.

NOW: In addition. MOST RV's (is this a "Parked" trailer or is it intended to be Mobile, RV's are Mobile)

Most RV's also have a 12 volt system.  This powers lights, water pump, furnace, control power to Fridge, Water heater, Air conditioners and most other stuff with the exception of the microwave and televisions  and of course your 120 volt wall outlets.

Finally, any outlet in a place that can get wet

Bathroom,, Kitchen counter,, Over the dining table,, Patio (outside) MUST be GFCI protected.. Usually that is one GFCI, usually in the master bath or half bath (but not always) and the rest of them "Chain" off that GFCI.. Mine was in the half bath, (Still is) but I just added a 2nd (End of kitchen counter) on a brand new circuit along with a chained outlet (right beside it) for better power in kitchen, it is labeled KITCH-2 (Kitchen circuit 2) 

Oh and the wire.. Most RV's for most outlets use 14 ga wires and "Quick box" I do not recommend those at all.  oh 14 ga is ok for 15 amps. but the quick box is junk

The one I added is 12ga bent around screws on the GFCI not punched down (Quick box) or poked in a hole (Most 15 amp outlets offer that option, including my GFCI)  12 ga.. Well ( though tit was a 15/20 GFCI (it's not) but I like it better, less voltage drop.. Bent around a screw means it can carry the FULL load, 15 amp breaker on one end, outlets on the other, standard Dual wall box.

WORKS GREAT once I pushed the RESET on the GFCI.
 
I may have mistakenly said, "electric" water heater but I'm actually using an on demand propane heater.

Actually the mistake was mine - I have you confused with another member doing a somewhat similar re-wiring project.

30A power quickly gets slim when you start running a/c or microwave. Ditto for hair dryers, toasters, and coffee-makers, most any thing that heats or cools. You will be fine as long as you know the amps or watts such appliances draw and stay aware of which ones are turned on at any one time. 30A = 3600 watts, and you can actually use only 80% of that for longer periods (more than about 30 minutes). If you try to run at 25A-30A for much more than that, you will find that the 30A plug and outlet get quite hot and soon shows signs of burned blades or wire connections.

You will want a battery and a 12v converter/charger to provide basic 12v power, even when connected to shore power.  It's a simple device that operates in parallel with the battery. You can get a combined 120v/12v power center that includes everything you need. The Progressive Dynamic PD4135 would probably be ideal for your needs.

http://www.bestconverter.com/PD-4135-35-Amp-Power-Center_p_612.html#.Wb04DtFrwdU
 
If you havent already bought a main disconnect AND you have a couple of spare circuits in your panel you could install a 30A breaker and connect your cord set to the load terminals of that breaker. (If you are going 50A, you would then install 2 pole 50A breaker and do the same.  You would put the 2 feed wires to the load side of breaker, green to ground and white to neutral bar).
Hope this helps
 
Progressive EMS doesn't fit with inexpensive. Something to look at.

https://progressiveindustries.myshopify.com/products/ems-hw30c-pid

 
Lou Schneider said:
One clarification, though.  Combination inverter/chargers are usually available only in large, whole house units.  For what you describe, you want a converter that changes 120 volt shore or generator power to 12 volts DC, then a separate inverter to change the 12 volt battery power to 120 volts AC.

Not up to date.  There are dozens of different inverter/chargers available for mobile use.  Xantrex makes the most desired ones. I use one in my commercial semi truck for my personal AC needs in the sleeper compartment and to charge batts when hooked up to shore power.  A true sine wave Xantrex Freedom XC 2000w inverter / 85 amp charger can be had for ballpark $500 in many online outlets.  Auto switching when shore power or gen set hooked up.  Panel where user can select the type of battery being charged so the multi phase aspects of the unit are tailored to the batteries being used including temperature compensating, limit the number of amps of incoming power used to charge the batts so the charger is not scavenging all the incoming power for the batts, when on shore power / gen set the IC passes thru AC power, etc.  The Freedom XC 2000 is a killer value package unit.

No need for both inverter and converter.  That is sooo old school.  The best way is one unit for everything, all user defined operation and controlled. 
 

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