# 30 amp shorepower instillation



## watcher (Sep 4, 2006)

Buddy of mine wants to install a 30 amp outlet/box for shorepower for his RV and I need some advice on what size wire to use.

Some info. I know the length of the run effects the size of the wire but don't know how far the outlet/box will be from the breaker box. I know he currently parks it not to far from the house so I'm guessing it'll be under 50 feet.

He currently doesn't plan to have anyone 'living' in the RV while its on the power he just wants to be able to run the AC and frig for a while to cool things down before they take a trip. BUT I know he has family visit from time to time so I have REALLY suggesting he sizes the wire to be able to handle a full load.

Now with that said my research suggest that 10/2 copper wire would be OK out to 75 feet or so. Longer than that and move up to 8/2. Does that sound right to ya'll?


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## farminghandyman (Mar 4, 2005)

#10 if it is close #8 if any distance and would be better,

I would consider running a set up with 240 volt, 4 wire, ground, neutral and two hots,

~~~~~~~~~~~~~~~~~~~~~

I have a RV box in a few places and I have used the 240 @50 amps, and I have breakered two 120 volt as well and there is room in my box for the RV 30 amp receptacle as well, the number of times before my portable welder did I drag out the welder to the box to weld up some thing I could not get in the shop,

this box here is similar to how I am set up, http://www.pplmotorhomes.com/parts/rv-power-cords/multi-outlet-power-box.htm
OR
http://www.homedepot.com/p/GE-100-A...it-Protected-Receptacles-GE1LU532SS/203393689


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## Harry Chickpea (Dec 19, 2008)

#10 solid copper s/b fine. The part that takes a beating is the plug and socket. Using a no-ox paste can help a little.


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## wharton (Oct 9, 2011)

Harry Chickpea said:


> #10 solid copper s/b fine. The part that takes a beating is the plug and socket. Using a no-ox paste can help a little.


 
Harry is correct. BTW, there are some "voltage drop calculators" on the net that do a great job of selling bigger gauge wire than you need. On a branch circuit like this, generally you need to be heading past 150' to see appreciable voltage drop on a normally sized wire. 

Another thing to consider here, as a general comment to all who have an interest in this topic...... A 30AMP RV supply is 30Amps at 120 VOLTS. The RV world is full of tales of woe from folks that had handymen, "electricians" and DIYers who did things like making an extension cord, or adapter to plug the RV into the home's dryer outlet, or assumed that the RV receptacle needs 240 volts, since it looks just like an old style dryer receptacle. On a 30 amp RV, sending 240 volts into the rig generally ends up running a few grand in repairs to the fridge, microwave, HWH, furnace etc..... So, it can be an expensive assumption. 

It's always a good idea to have a breaker at the receptacle to shut it off, before plugging and unplugging the cord. Plug ends really arc, and get burned otherwise. Newer campground power pedestals are now equipped with with warning labels advising that the breaker be shut off when connecting and disconnecting, and citing the code requirement to do so.


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## watcher (Sep 4, 2006)

Thanks for the info. I'll have to talk to him about what kind of box he bought i.e. with or w/o a breaker. I'll suggest he use one with a breaker.


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## notthereyet (Nov 17, 2011)

Would also recommend sinking a ground rod at the connection point and make sure it's bonded to the house ground. When (not IF) a strike occurs, you want it to hit the ground ASAP.


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## wharton (Oct 9, 2011)

notthereyet said:


> Would also recommend sinking a ground rod at the connection point and make sure it's bonded to the house ground. When (not IF) a strike occurs, you want it to hit the ground ASAP.


 Not a bad idea, unless you ignore the highlighted part in red. A driven rod at the end of a branch circuit can be helpful, harmless, or a safety issue depending on whether or not it's properly bonded to the receptacle, the enclosure, and the ground wire of the circuit.


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## watcher (Sep 4, 2006)

wharton said:


> Not a bad idea, unless you ignore the highlighted part in red. A driven rod at the end of a branch circuit can be helpful, harmless, or a safety issue depending on whether or not it's properly bonded to the receptacle, the enclosure, and the ground wire of the circuit.


Safety is very important here so. . . We put a ground rod at the box then do we run the ground from the house to the rod then to the box or do we run the ground to the box then run a second wire to the rod. My thinking would be to put the rod inline with the ground from the house. Sort of like a second ground rod for the main breaker box while acting as a direct ground for the RV box.


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## wharton (Oct 9, 2011)

There is no reason that an additional ground rod has to be driven, or is required, and it would be quite unusual. If you do install one, the wire attached to the ground rod needs to connect to the receptacle, the metal box that the receptacle is installed in, and the ground wire of the circuit that started in the main electrical panel.


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## notthereyet (Nov 17, 2011)

I'm not an electrician, nor do I play one on TV or the 'net, but I've been working with electricity in various forms for nearly 25 years and like to think I have a pretty good understanding of it.

Wharton's post inspired me to look around, and indeed, I can't seem to find any bit of code that requires additional grounding, but there is a reason for the recommendation. That reason is lightning, which will always follow the path of least resistance and does not discriminate.

For $11.28 at Lowe's, adding an additional ground is a pretty cheap way to help protect your lives and your property.

IMO, if you're putting in shore power for an RV, I would start with a double pole 50a breaker at the main, a 4-conductor #8 (25') or #6 (50') or even #4 (100'), and ending at a service panel with an additional ground rod. Now you have safe shore power for newer and older coaches, as well as a 20a convenience outlet.











If you want Internet, consider using a pair of media converters and a bit of fiber rather than extending Cat5 Ethernet. If you must use Ethernet, use shielded cable, shielded connectors, and make sure it's bonded to ground at both ends.

If you want to extend your phone line, again use shielded cable and make sure it's bonded to ground at both ends. At the house, be sure to connect it in at the Telco Demarcation box. Your local telco should be willing to come out to make sure that it's connected properly.

Yeah, all this is probably overkill, but you could always run around and try to disconnect everything before lightning strikes. Assuming, that is, that you can predict when and where it will hit.


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## Harry Chickpea (Dec 19, 2008)

If you want to extend your phone line, again use shielded cable and make sure it's bonded to ground at both ends.

Nope. Common error. Shields for audio level signals get grounded only at *one *point. Otherwise they become conduits for stray currents and induce noise. One expression for a part of the issue is known as "ground loop."  It was one of the most common things my dad and I had to correct in P.A. and other audio systems.

The OP situation is within 100' of the electric entrance (grounds from tele and cable/internet should also be bonded to the ground there). There is no real need to go overboard at that short a distance.


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## wharton (Oct 9, 2011)

notthereyet said:


> Wharton's post inspired me to look around, and indeed, I can't seem to find any bit of code that requires additional grounding, but there is a reason for the recommendation. That reason is lightning, which will always follow the path of least resistance and does not discriminate.
> .


 A better reason for a properly bonded, interconnected ground rod at the receptacle is something known as a difference of ground potential. This was an issue in several aluminum sided rigs I have owned, and would provide temporary power to with a standard extension cord and 15 to 30A adapter. The issue is that the trailer manufacturer would bond the neutral to the ground inside their panel. They would also bond the siding to the trailer frame. So, any unbalance in the load would try to return to ground by taking the long path back the extension cord, or if you were unlucky enough to be soaking wet, and touch the side of the wet trailer, it would go to earth by giving you a good shock. In theory, an additional driven rod would lessen or prevent this issue from happening.


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## notthereyet (Nov 17, 2011)

Harry Chickpea said:


> If you want to extend your phone line, again use shielded cable and make sure it's bonded to ground at both ends.
> 
> Nope. Common error. Shields for audio level signals get grounded only at *one *point. Otherwise they become conduits for stray currents and induce noise. One expression for a part of the issue is known as "ground loop."  It was one of the most common things my dad and I had to correct in P.A. and other audio systems.
> 
> The OP situation is within 100' of the electric entrance (grounds from tele and cable/internet should also be bonded to the ground there). There is no real need to go overboard at that short a distance.


Yes, you're right in that the short distance minimizes the risk, but the risk is still there. Proper lightning protection is cheap and there is absolutely no reason not to do it.

Audio wiring and phone lines are two completely different animals.

Any conductive line between structures should indeed be grounded at both ends. Look no further than the service entrances for your phone/cable on the side of your house. By your logic, the 50' between the pole and the home means that grounding at the pole is sufficient. This is not the case, and when extending that connection to yet another structure, additional grounding is warranted.

At the very least, a few pennies worth of wire doesn't hurt.

If there's any doubt, consult with an electrician familiar with low voltage/data systems.


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## Harry Chickpea (Dec 19, 2008)

Audio and phone are _not_ two different animals. Phone carries a ringer current but in all other aspects is a balanced audio line. Scrounge around and you'll find questions about electric fence static getting into phone lines. They also pick up local AM radio stations.

Grounding the centertap and case of a pig has everything to do with the long expanse of wires going into the hot side and a* reliable* provider ground that is *not under control of a homeowner*. It has NOTHING to do with the short distance between pole and entrance. Some homeowners are idiots. Trimming around the entrance can cut or dislodge a ground tap from the rod.

I've gone over this too many times before over the years to go again into detail, but here is the 15 cent tour. Lightning strikes follow the general rules of high voltage mixed frequency electric discharges. A large "cloud" of charge in the air will go over an oppositely charged area of earth, and the two charges will localize into a smaller area where the strike has the potential of occurring. These areas can be acres in size. Milliseconds prior to a "strike" there will be a number of false leaders that rise from the charged ground, generally centered around metallic pointed objects that have an excellent ground connection, but also around other objects like trees that can carry electricity through the rainwater on trunks or the xylem under the bark, or even the stems of grasses. Most leaders don't connect, but one, two or three WILL support sufficient current flow to connect and then allow enough flow to ionize the air, creating the familiar visible lightning "bolt." (There are also dangerous discharges that are NOT visible.)

After initial discharge, current flow can repeatedly reverse through that ionization area as pockets of charge are discharged, electrons move from different areas and unequal charge areas seek to normalize. This is a large area event.

If you are still thinking your way of grounding is better even though the effectiveness is demonstrably minimal, I have even more proof of why it isn't:

Consider the regular news reports of golfers and others who have taken shelter under a tree in a storm. Lightning hits the tree (_*NOT* the golfers_) and all the golfers around the tree fall down dead or injured. Repeating - the golfers are not struck and are only in the VICINITY of something that was struck.

The ground in the immediate area of a strike is subject to tremendous currents and voltages as the charge in the earth tries to reach up, and then the charge from the cloud attempts to find the paths of least resistance to spread throughout the soil in the area. Depending on the conditions of the soil and the discharge, an area from thirty to a couple hundred feet can be a dead zone. (You'll find ample internet photos of lightning killed dead livestock backing this up.) Even with a properly driven ground rod, some discharges will run across wet grass or soil on the surface of the ground. That is the nature of the beast. I had one fellow report a discharge cross the wax on a linoleum floor to take out an X-ray machine, even though the building was properly grounded according to the strict codes required in medical facilities. High frequency high voltage acts completely differently than normal mains power or battery power.

Having the ground rod at the electric entrance places those stray charges further away from any RV or person standing near it. Having a second ground rod almost under the person's feet could literally be a death sentence for that person. I doubt you want that.

One single-point ground with sufficient lack of resistance (there is a special meter used to measure this) is all that is needed to properly ground an area this small. Once you get a structure a few hundred feet away your concerns become more valid and the code requirements start getting weird.


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## BadFordRanger (Apr 26, 2014)

Watcher, and anyone else that don't already know the truth about wire size, 15 amps requires a #14 gauge wire!
20 amps requires a #12 gauge wire! 
30 amps requires a #10 gauge wire!
40 amps requires a, #8 gauge wire! 
and 50 amps requires a #6 gauge wire!
Now you have approximately 3% drop in voltage for every 100 feet! 
Now there is something that most people don't know or understand, and that is just because you have a top of the line 200 amp breaker box in your home, doesn't mean that you have 120 volts at your house! 
If someone calls me to check on an electrical problem, the first thing that I do is check the voltage! I have seen it as low as 108 volts, which will cause motors in refrigerators, air conditioners, and even air compressors to fail prematurely! They will cause a heat build up the plugs and receptacles and burn them both up! 
On the other had, I have seen voltage as high as 128 volts, which is great for motor driven "machines" but will blow incandescent light bulbs like crazy! 
Sometimes the electric company will come out and check the transformers on the pole and they might make a change or they might not! 
All in all, the closer to 120 volts, the better off you are, but as I said, it varies! It is all in the location of your house, how many volts are in the high tension wires going down the street, or road, and how far you are away from the transformer! 
But say you only have 115 volts at the breaker box! That is already low! Now take 3% of that away for a 100 foot run! 
That leaves you with about 111.5 volts and if you add a 100' drop cord to that, you loose another 3% of that 111.5 volts so you only have about 108 volts! 
If you are using a circular saw like that and push it hard ripping 2 x 10's, as I do a lot to make 1" x 2"'s, it will heat a saw up fast and used hard, it will burn it up! Same thing with air compressors! Been there and done that! 
In that situation you are better off to run a 25' or 50' drop cord out the closest window and from the closest receptacle to the breaker box! 
Hope this helped!


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## watcher (Sep 4, 2006)

BadFordRanger said:


> Watcher, and anyone else that don't already know the truth about wire size, 15 amps requires a #14 gauge wire!
> 20 amps requires a #12 gauge wire!
> 30 amps requires a #10 gauge wire!
> 40 amps requires a, #8 gauge wire!
> ...


I'll have to check to see where he wants the outlet before I make the call on the wire size. I will check out the voltage because one of the main reasons he wants it is so he can run the AC and frig for a day or so to cool things off before they leave and make it more comfortable loading stuff.


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