Need to wire an RV over a long stretch of ground

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  #1  
Old 07-27-14, 01:03 AM
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Question Need to wire an RV over a long stretch of ground

Hello Everyone!
Names' Wayne, I am coming here seeking [hopefully certified professional] help with an electrical project we have going. I am very familiar with running electrical through the house, but I have never done a long distance outside run.

We need to run power to an RV that is going to be 300 feet away from our main panel. We cannot move the RV any closer, no way no how.

It of course runs off 120v and needs a consistent 30 amps. There are 3 bends (5 if you count the vertical 90's to get to the panels) on the path the wire needs to be laid. My main panel already has one sub panel running off it and it is a Square D QO. (don't worry, the system is not over-taxed)

I have come to 2 conclusions on how to do this, I am hoping to get confirmation that I have the right idea or that I am off. I hope a professional can point me in the right direction if I'm all screwed up.

Given the Length I did calculations for voltage drop and came to the conductor sizes listed below

Option A: Run the Entire length via 120v to an RV receptacle.
~30 Amp 120 breaker
~2 AWG copper stranded (Hot and Neutral)
~4 AWG copper solid (Ground)
~2" Electrical PVC Schedule 40 (buried 18")
~30 Amp 120v RV receptacle With Outdoor Box

Or

Option B: Run a 240v line to a new Sub-Panel and then do a very short 120v 10/2 run to the receptacle. (< 10')

~60 Amp 240 breaker
~2 AWG Copper Stranded (2 Hots and a Neutral)
~4 AWG Copper Solid (ground)
~2" Electrical PVC schedule 40 (buried 18")
~Another 4 AWG Copper solid to buried ground stake
~Sub Panel- Outdoor Rated (70Amp)

Then from the sub panel run:

~30 Amp 120v breaker
~10/2 Copper solid (with ground)
~Either 3/4" Electrical PVC sch40 or Liquid Tight Flex Tube
~30 Amp RV receptacle (with outdoor box)

---Questions---

Do I have the right idea here? If no- what would you suggest?

If Yes;

Is Option A even Viable? (I'm just curious)

Option B seems like the best choice to me and only slightly more expensive to do. running the 60Amp panel seems like less of a chance of having problems with the voltage drop.

Is there any reason I would want to run a larger breaker? I don't see us ever needing more electrical / power out there.

Are my calculations for wire gauge correct? I should use THHN wire correct; or are there other choices?

I want to make sure it has ample power, but if I there are any cost saving avenues, I'd love to save the $$$.

------
Thank You all Very Much for the help! I really appreciate it and just want to do this right. I am very confident in my ability to do this correctly, But I wanted to double check with some more experienced people before I got started to make sure I am pointed in the right direction. I am sure some of you will tell me to just hire an electrician, but with the cost of the project, we cannot afford that (& I take a lot of pride in learning how to do things correctly).

~Sincerely - The Wayne
 
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  #2  
Old 07-27-14, 04:34 AM
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Personally, I would run some #2 URD (direct burial) to a small sub panel protected with a 60 amp breaker (smallest breaker #2 would fit) then, run your 30 amp RV receptacle from that.

Nothing wrong with running aluminum. You can get 2224 aluminum URD for just over $1/ft.
 
  #3  
Old 07-27-14, 05:05 AM
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Running 240 volts to the RV will not help the voltage drop as the RV is only a 120 volt load. However, if I was going to do it I would also install a 4 wire feed just to have the availability 240 volts and it would double your available load with no added voltage drop.

I would agree with Wirenut. #2 aluminum would keep your voltage drop to less then 5% and the direct burial would be easier to install. If you are sure there will never be anything else by the RV a 120 volt, 3 wire feed would be fine.
 
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Old 07-27-14, 08:00 AM
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Thanks for the prompt replies guys.

I was in no way planning on putting 240 to the RV, that would just blow it up internally. But it sounds so far like the agreed method is a 240 line to a sub panel and then down step to the 120 RV line.

I have never used aluminum, but when I did the calculations via aluminum line resistance I came up with that I would need to use a larger 1/0 line rather than the #2.
-Also I am in the swamps outside of New Orleans where the weather is harsh, humidity is insane. My understanding is that aluminum is more prone to oxidation, this concerns me. I've seen the humidity and weather destroy just about everything out here (tools rust inside the garage)d

I am aiming for a voltage drop of no higher than 3%. Am I mistaken with this, I've read 3% on the main, 5% on a feeder / branch. I thought this would be considered a main because of the new panel.

Lastly, no matter what I am gonna run conduit because I simply dont want to risk that wire ever being broken, its not that much more expensive.
Is there any reason I wouldn't want to run conduit?
 

Last edited by Wayne Ballou; 07-27-14 at 08:21 AM.
  #5  
Old 07-27-14, 08:38 AM
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Is there any reason I wouldn't want to run conduit?
It is not code prohibited but it is hard to pull, especially with the number of bends.

If you are sure you want only 120v you could use aluminum single conductor such as XHHW-2. #1 or #2 would give an acceptable voltage drop, specially if no large motors. If you use adequate size conduit you could always pull a fourth wire later. Ground could be #6.

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Calculator at: electrician2.com voltage drop calculator
 
  #6  
Old 07-27-14, 08:48 AM
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I was in no way planning on putting 240 to the RV, that would just blow it up internally.
You misunderstood. What I am saying is that since the RV load is a single 120 volt circuit there is no benefit of running a 240 volt circuit because the load would only be on one hot. Unless you think it would be handy to have the extra capacity.

The Code informational note for voltage drop says that feeders and branch circuits should be limited to 3% each and 5% for a combination of both feeders and branch circuits. There is no not for "main". You are running a feeder if you plan to have an overcurrent device at the end of the run, otherwise it is a branch circuit. Note, that this is only an informational note and not a requirement of the Code. Aluminum if fine if it is properly installed.

Is there any reason I wouldn't want to run conduit?
Yes, because a 300' pull in PVC conduit will be quite difficult. Wire is not to be installed until the raceway is complete, you should not push it in 10' at a time. Plus, you have too many bends so you will need a junction box some place to limit the bends to no more then 360 degrees total. if you don't want it to get hit then bury it deeper then the 24" requirement.
 
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Old 07-27-14, 10:13 AM
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Thank you for your answers (I will continually repeat this); And your patience with helping me understand how this needs to be done. I am sure I am asking (and going to continue to) some questions which are making you raise eyebrows and say to yourself that I need to hire a professional (again not possible)... I appreciate you helping me understand what is necessary to make this happen correctly.

You misunderstood. What I am saying is that since the RV load is a single 120 volt circuit there is no benefit of running a 240 volt circuit because the load would only be on one hot.
Thank you for clearing this up, So you are saying I could run the sub panel with only one leg of power to it and it would operate as a 120v sub panel; no difference in voltage drop? Doing it this way is the only reason for the sub panel at the end of the run to have an over current device in place?

You are running a feeder if you plan to have an overcurrent device at the end of the run, otherwise it is a branch circuit.
Now I am curious if I would even want / need the sub panel [a feeder, then branch- to RV off it] or if I should just run it as one long branch to a receptacle...

Yes, because a 300' pull in PVC conduit will be quite difficult. Wire is not to be installed until the raceway is complete, you should not push it in 10' at a time.
I was planning on doing it the 10' at a time method- errrr and well not as much "Push it" but more pull the wire strait, sleeve the conduit onto it and then move the conduit down the length of the wire very carefully to avoid any scuffing / catching. Another Idea I had was to use a pull line and do it 10 feet at a time, but only have the pull line go out through each 10' section, then move up [pull] the wire after I connect each 10' piece. I was planning on using the spigot/bell conduit that sleeves over itself. Can you explain to me why either of these are bad ideas? (I assume this is an idiots question, sorry)

Plus, you have too many bends so you will need a junction box some place to limit the bends to no more then 360 degrees total.if you don't want it to get hit then bury it deeper then the 24" requirement.
What is the effect of going over 360* bend?
By junction box do you mean a box where I come in and wire nut or connect one line to another, or are we talking another sub panel (overcurrent device)?
How would that create less disruption than a bend itself? Is there more wiring in the box itself than just connecting one wire to the next, that I am unaware of? Or is it just the connection of the two lines to each other?
I will throw together a quick drawing of the run implied for feedback on that.

if you don't want it to get hit then bury it deeper then the 24" requirement.
I am out in the boonies and this line will never be inspected to code requirement [part of the reason I very much want to do it correctly.] I am not worried about a violation of code, but more proper function of the line.
 
  #8  
Old 07-27-14, 10:33 AM
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Push it" but more pull the wire strait, sleeve the conduit onto it and then move the conduit down the length of the wire very carefully to avoid any scuffing / catching.
The conduit must be completely assembled and solvent cement dry before cable or wire is pulled in to prevent the cement from damaging the insulation on the cable or wire.
What is the effect of going over 360* bend?
Code violation.
Is there more wiring in the box itself than just connecting one wire to the next, that I am unaware of? Or is it just the connection of the two lines to each other?
Just connections but the box must meet requirements for above ground use are if buried special water proof connectors must be used in an electrical hand hole box flush with the ground.
So you are saying I could run the sub panel with only one leg of power to it and it would operate as a 120v sub panel
Not how I read it. If you ran as 120 no need for the box so I think he meant to run a 120/240 sub panel for future proofing.... but wait for him to clarify.
 
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Old 07-27-14, 10:39 AM
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What is the effect of going over 360* bend?

Code violation.
In addition to being a code violation, with over 360 degrees in bends you cannot pull the wire.
 
  #10  
Old 07-27-14, 11:18 AM
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I love you guys.

I hope you don't think I am a total idiot because I am learning a lot here and genuinely interested. As a DIY warrior, I actually plan on getting into school this year for electrical- I currently do animal rescue for a living and love it; but it doesn't always pay the bills. I can't take on an apprenticeship currently because of conflicting hours, so I am looking locally for technical schools where I can go to class at night to learn everything and open new doors of opportunity for work in my future.


What is the effect of going over 360* bend?
Code violation.
In addition to being a code violation, with over 360 degrees in bends you cannot pull the wire.
My question to this is would it effect the performance of the line or just violate code? (may sound like an idiot here again) I am not too worried about violating code, I just want it to work properly and safely. (then I probably answered my own statement that it is unsafe to work outside code permits)

but more pull the wire strait, sleeve the conduit onto it and then move the conduit down the length of the wire very carefully to avoid any scuffing / catching.
The conduit must be completely assembled and solvent cement dry before cable or wire is pulled in to prevent the cement from damaging the insulation on the cable or wire.
Could I do this slowly via the other method I had mentioned allowing each 10' section to be glued and dry with only the pull string pulled through it, after it dries then move 10 feet up, wash rinse repeat?
or would it be better at this point to use a different conduit and compression fittings?
[Stupid question Now: how important is it to have it solvent welded? is this to keep it water tight beneath the surface?]
 
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Old 07-27-14, 11:21 AM
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I came into the thread late but I don't see any mention of quantity of bends listed. You should limit yourself to one bend (90) at each end.

I've been pulling large wire underground all week. You can use a vacuum and a small plastic bag to pull your pullstring into the conduit when done. After the string is in you can pull a rope in.

You've got a good pull there. Make sure you have wire pulling compound to help with the job.
 
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Old 07-27-14, 11:25 AM
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Here is a wiring diagram I just threw together to depict the way it had been planned:

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If you want a good laugh now, The 'Red Run' was originally dreamt up by a co-worker who feels he has all the electrical knowledge to tackle this project, "NO PROBLEM" he says.
He was planning on doing it with a 30amp break, 10/2 w/ground direct burial, to a normal house outlet (15amp rated, I checked), then use the adapter from the RV plug to a house outlet.

When I told him I thought his idea was messed, he re-assured me how confident he was this would work correctly.

I am sure glad I don't trust him. I drew up the new run in my head (blue line) and it does come to a full 360*; Can you do that? Does it have to be less than 360* or can it be equal to?

--- If my wiring idea of how to do this is messed too, what would one recommend? if a junction box is needed, where would be the best placement to do so?
 
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Old 07-27-14, 11:35 AM
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At your house, you can use LB's as pull points. They break up the continuous 360d.

[ATTACH=CONFIG]35418[/ATTACH]
 
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Old 07-27-14, 11:44 AM
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At your house, you can use LB's as pull points. They break up the continuous 360d.
Ahh! So I can use these as "small junction boxes" and just wire nut my lines together inside them?

*edit- I have never spliced/connected 2 gauge... I'm assuming I need to use lugs of some sort, is this even possible in one of these LB's?*
 
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Old 07-27-14, 11:51 AM
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No.... they are pulling points. A place where you can pull the wire in two different directions. You can substitute the LB with a plastic junction box and then splice in there. You can buy the boxes with or without knockouts. I usually drill my own.

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  #16  
Old 07-27-14, 01:36 PM
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Inside your house run SER to a junction box outside, transition to pipe or direct burial.

Keep in mind also, this voltage drop calculator doesn't mean you would need to run #2 the whole way. You could always run, for example, #2 200', set a junction box and run the remaining 100 ft in #4 or whatever.

Just the wire can't be smaller than your OCPD.
 
  #17  
Old 07-27-14, 07:16 PM
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Okay I am learning again now-
so the 360 rule is so the pull can actually be done, Not because of voltage loss or danger to the line, right?
- Meaning when you talk about using LB's as pull points, it's simply breaking the pull from one long pull into smaller length multiple pulls which are less degrees of pull?

Thus meaning, I mis-understood and the entire 300 can all be one- Non-spliced cable.
--(that's what i thought you guys meant by you can't have over 360- that I had to literally splice the cable and it didn't make sense to me when I first thought of it)--

So- If I do the wiring the way I drew it with the Blue line, I can use LB's going up into the attic and back out, to make the house wiring super easy- then do the big long pull that will only be effectively 180* of bend. Correct?

I understand the rest correctly and I am going to try and do it as you all recommended lay the conduit and glue- then after it dries do the 'Big Pull'

Follow up dumb question is- Can I run the wire through the attic free of the 2" conduit, like I would a romex line? I don't see why not...

After redoing the calculations, I am leaning on the aluminum conductor, because of it's much cheaper price & all four wires come sleeved together. This is given it can hold up in this swamp humidity and severe weather... Anyone wanna chip in on that one? I am probably being over cautious.
 
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Old 07-27-14, 07:38 PM
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Can I run the wire through the attic free of the 2" conduit, like I would a romex line? I don't see why not...
Separate individual conductors must be in conduit and cannot be run open like a NM cable (romex). That was why the suggestion was made to use a junction box in the attic to transition to an SER cable that can be run open through the attic and on to the panel. SER cable would have 3 insulated conductors and 1 bare ground conductor.
 
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Old 07-27-14, 07:52 PM
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USE Schedule 40 Long Radius Sweeps......30 OR 36 IN. RADIUS........TO TURN UP AT EACH END....IT WILL HELP A LOT ON THE WIRE PULLING....USE THE PVC PIPE CLEANER AND LOTS OF GLUE ......... HAVE YOU LOOKED AT THE 4 WIRE 100 AMP TRAILER SERVICE AT LOWES...........USE LOTS OF WIRE LUBE 1 OR 2 GAL.LUBE IS CHEEP....STOPING HALF WAY IS NOT GOOD
 
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Old 07-28-14, 07:03 AM
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Nothing wrong with running aluminum. You can get 2224 aluminum URD for just over $1/ft.
This is probably the best suggestion for a beginner who has never pulled wire in conduit before because this product is to be direct buried without conduit. There is no way I'd recommend you attempt a 300 foot wire pull on your first attempt. The 2-2-2-4 suggested above is commonly called mobile home feeder and is direct burial rated, this is what I would suggest too.

http://www.southwire.com/ProductCata...prodcatsheet15

Some box stores stock this product, but the ones who don't can show you how to order it from their website, cut to the length you want. If you decide to go ahead with the 300 feet of conduit, do not attempt to pull this product in the conduit. The twist of the conductors is great for keeping the conductors manageable for direct burial, but it also makes pulling in conduit much more difficult even for a pro with specialized pulling equipment.
 
  #21  
Old 07-28-14, 08:42 AM
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That is what I am thinking Joe,

After much reading, pricing, etc I have decided to go with the 2224 URD line- to run it up, through the attic, down the opposite side of the building and then the long strait run underground.

My big concern is still the conduit. The ground out here is really hard to dig out (even with a ditch witch)- I don't know if I can get deeper than 16" in some areas might only be able to get 12" deep. It is constantly flooded. Vehicles & heavy trucks drive over the area when I am going to be laying the line all day long. I am really worried about the line being damaged if buried without a conduit sleeve.

Can somebody offer a little more newbie advice on this? am I worrying too much or should I sleeve it in conduit? I could run a much larger conduit than necessary for the line if that makes it easier to pull...
I just really don't want to have the line damaged and have to re-do this project down the line.

I am doing my final stages of planning and I'm going to go get supplies in the next few days.

Thanks guys!
 
  #22  
Old 07-28-14, 10:15 AM
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I have decided to go with the 2224 URD line- to run it up, through the attic, down the opposite side of the building
Not all URD is rated for use in a building. Probably easier anyway to use 6-3* NM-b (Romex) in the house and then transition to the URD in a junction box.

*Yes 6-3 not 2-3. The voltage drop won't be large enough in the house run to need larger and it will be easier to work with.
 
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Old 07-28-14, 06:42 PM
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The ground out here is really hard to dig out (even with a ditch witch)- I don't know if I can get deeper than 16" in some areas might only be able to get 12" deep. It is constantly flooded. Vehicles & heavy trucks drive over the area when I am going to be laying the line all day long. I am really worried about the line being damaged if buried without a conduit sleeve.
Under normal circumstances, direct burial wire needs 24 inches of cover and conduit needs 18 inches of cover. How hard is the dirt or is it full of rock? The flooding isn't an issue, but heavy truck traffic is. Are there specific roads or driveways where these trucks travel? PVC conduit won't protect the URD from heavy trucks driving over it unless it is very deep. IF there are specific roads, you need galvanized heavywall sleeves under these roadways and they should maybe be as deep as 30 to 36 inches in those areas. An alternative to galvanized heavywall sleeves might by HDPE conduit sleeves in those areas, but they would still need to be deep.
 
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