I'm in the process of setting a RV in my back yard. The run is 150 ft long and will be buried. The RV is a 30 Amp, 120 V System. Will be running TV, PC, Refrigerator, Microwave, Toaster, Lights and Washing machine, of course not all at the same time! Planning to use PVC Schedule 80. Ground very soft and sandy. What size wire should I use? All 3 of them? PVC size? How deep?
For the full 30A load, the least expensive option that doesn't involve a direct bury cable would be to pull an aluminum 2/2/4 direct bury URD/USE triplex cable through 1" Schedule 80 PVC conduit, although it'll be a very tight fit (234mm^2 used out of 236mm^2 available). If you wish to go with Ed's 24A number, I'd use a 6/2 W/G UF cable instead -- NM has no business being run in outdoor conduits! While you could run individual 4 or 6AWG copper THHN/THWNs in the conduit, that'd be a bit costlier than the UF or URD cable, especially for 4AWG.
(If you use the URD/USE cable -- the 2 AWG wires are the hot and neutral, while the 4 AWG wire is the grounding conductor.)
I used 24 amps as the max load and came up with. #6 Copper conductor will limit the voltage drop to 2.66% or less when supplying 24.0 amps for 150 feet on a 120 volt system. 24 amps is 80% of the feeder. southwire voltage drop calculator is a handy tool to check voltage drop without having to do the calculations your self. 3% is the maximum voltage drop. THWN copper #6 (3 conductors) can be used with 3/4" PVC schedule 80 per table 9C in the 2014 NEC. I will use slightly larger conduit with PVC if there are more than 2 90's or pull soap on the wire for long runs this makes the pull easier. If you believe the load will be closer to 30A #4 copper would be needed and 1" schedule 80 PVC conduit this would have a 2.16% voltage drop.
I would use #8/2 (three wires: black-hot, white-neutral and bare-ground) gauge wire into your electrical box (connected to a 30A breaker) and out to a convenient exterior receptacle close to where you will be parking the RV (similar to what you might see in an RV park)
Here is an example of the wire (you will need to go to your local Home Depot/Lowes/etc. to get the custom length that you need to run all the way from your RV to the electrical box):
I would surround this wire with 3/4" or 1" (I would go with 1" to make it easier to pull) PVC Schedule 80.
I would bury it below the frost line if at all possible. Here is a chart to give you an idea of your local frost line:
You might want to rent a walk-behind trencher to make this burying process easier; something like this:
At the location where you will be bringing up the wire to an exterior receptacle (I would build a solid little post with some treated wood to protect and mount the exterior box):
Depending on the power connection that comes with your RV, you would then connect it to your exterior receptacle with a simple RV power cord, like this:
Depending on your area (the more rural your area and the friendlier your neighbors, the easier it should be to DIY), you might want to consult an electrician and your local inspector's office