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Old 09-03-2015, 10:50 AM   #15
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You can use aluminum outside, just run the cable from pedestal to the outside of the house. Use conduit where its day lighted.
Use copper inside the dwelling and to the outside wall where it meets the aluminum. Use proper Al/Cu connectors.


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Old 09-03-2015, 01:51 PM   #16
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You need to anticpate what your largest draw will be in the future. Are there thoughts of upsizing where you would need 50A? Or possibly hosting more than one guest at a time?

While what you ordered is overkill for now, it may not be in the future. The incremental cost of overbuilding now will save time and money in the future. The wire you run now will be the limiting factor for future expansion.

The breaker you put in your main panel must be smaller or equal to the ampicity of the wire you run, taking into account the length of the run. It is this breaker that ultimately protects the wire in the run to your pedistal sub panel.


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Old 09-03-2015, 02:42 PM   #17
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Originally Posted by israndy View Post
I think technically if you do wire up the 50 amp you actually need a second run of wire for the 30 amp outlet.
Most likely not true. Most RV pee-assembled pedestals are considered subpanels and use a common bus to feed all of the circuit breakers. There is no provision to add an additional 30A feed in addition to the 50A feed. You need to size the feed wires to meet the overall utilization need of the pedestal. For what the original poster is installing, at minimum the feed needs to be capable of supplying 50A and 100A if all three outlets are to be used at the same time.


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Old 09-03-2015, 02:48 PM   #18
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I think technically if you do wire up the 50 amp you actually need a second run of wire for the 30 amp outlet. If you put a full draw on the 50 and ALSO put a draw on the 30 you would be overcapacity and run your wire hot until the breaker went. Same for the 20/15 amp outlet. If you are ignoring code and never intend to use more than one outlet label it so. There should be a lockout to prevent more than one working, but I don't know of any pedestal that supports a lockout, they just have the extra circuits run.

....

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Randy is right. For a normal RV pedestal there would only be either a 50A connection or a 30A connection. If there is any thought of using both connectors simultaneously the 30A receptacle should be fed by its own conductor, should have its own neutral, and should be protected by its own breaker.

Reviewing greggoro's response (shame on you for dragging in reality) the pedestal may not be wired to allow the use of the 50A and 30A circuits simultaneously. If not, using larger wires and a larger breaker at the source may not be a good idea.

Regarding the wire selection of 2/2/4/6, as I read the code, if he needs #2 for the hot wires (I don't think he does) then he should be using #2 for neutral. A different wire size for neutral is only permitted for 240V loads. The 50A RV setup is split 120 loads and so should have the same size neutral as the primary conductors.

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Old 09-03-2015, 04:29 PM   #19
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Matthorr - much speculation in assisting you can be put to rest if we knew exactly what pedistal you purchased.

Manufacturer and model, please.


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Old 09-03-2015, 04:40 PM   #20
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Check your local standards. No municipality in our area and maybe in the entire state permits new or add-on wiring using Aluminum. CoAlR switches and outlets or copper pigtails to existing aluminum wiring are permitted but only when the wiring is grandfathered under the code. Sometimes jackleg electricians will use aluminum wiring but when there is a fire and that is found, the fire insurance companies will not pay off. Aluminum may seem cheaper in the short term but in the long run it can be VERY expensive.
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Old 09-03-2015, 04:54 PM   #21
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See post #5. Again, I would NOT seek advice from any other source but a licensed LOCAL electrician who KNOWS and FOLLOWS your applicable state and local codes.

Any other path is foolish and potentially destructive!!


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Old 09-03-2015, 05:10 PM   #22
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Originally Posted by nrgtrakr View Post
Not an electrician, but a stationary engineer listening in ...
Wondering why not a 30 or 50 amp box for a 30 amp trailer?
Curious about what the electrician will say about the capacity of the source box and total load.
Guessing 2-2-4-6 (hot-hot-neutral-ground) in conduit - both in the house and underground.
We used nothing but copper when doing additions in hospitals, but I never asked why.
The extra 20A circuit will allow for a heated water hose, for example, or an outside light. The easiest would be to just run to a single 30A receptacle, but that would be the easy way out I figure that the hard part is digging the trench, so I might as well provide for more than I need an not have to go back later.
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Old 09-03-2015, 05:22 PM   #23
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Originally Posted by jdalrymple View Post
I am not an licensed electrician, but I too understand electricity.


For 50 amp RV loads, each of the conductors must carry a full 50 amp load. Because none of the appliances are 240 volts, the neutral conductor gauge must equal to the line conductors.

I believe you are on the right track on using romex in the stud walls and splicing to the 2 ga inside an approved box in the crawl space.



We shall see what others say.


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JD
The NEC does allow for a reduced neutral. BUT... I believe that is under the assumption that each phase will be roughly balanced, so that less than the full current draw will run through the neutral. Looking at the chart, for 4 ga AL the max ampacity (@75C) is 65A. The layout of the pedestal is:
Phase X - 50A + 30A
Phase Y - 50A + 20A
So worst-case is 80A down the neutral (assuming you connect 2 trailers to Phase X, and don't have anything connected to Phase Y).
If you use 2 ga AL, the max ampacity is 95A so it is safe.

*I* would remember to not connect both the 50A and 30A, but the next guy might not know the limitation. So I would have to either put a 60A breaker off the main or get a 2 ga neutral.
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Old 09-03-2015, 05:28 PM   #24
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Just wondering about the aluminum,
Lewster. I had a licensed electrician install a pedestal with 50amp on our rural property, aluminum was half the price, and the panel is almost 200' away from the pedestal so the savings was significant. ( can't remember what gauge, I would have to check). Works great, with everything on, 2 a/c's, electric water heater, microwave, and everything else I could turn on at once. I have a surge protector and the voltage is good. Just wondering, am I going to have problems in the future because I used aluminum?


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I know AL has a bad reputation, but it is quite common in service entry (assuming of course that the connectors are rated for AL). I'm comfortable using AL and my checkbook certainly is...

Thanks, Lewster, for the advice on wire size. I'm not sure why the ground wire would need to be equal size, though. It shouldn't carry current long enough to heat up.

I also agree that hiring a licensed electrician is the smart thing to do, but I want to at least understand the requirements. I am very comfortable doing the work, but I do want to be certain the materials are safe.

AL should be safe if the connectors are rated for AL and properly tightened. AL expands and contracts more with temperature (and is more prone to corrosion), but if properly torqued and with modern alloys is safe. Almost all new homes have AL running into them (just not inside house wiring - old AL wiring I believe is almost 100% BAD and needs to be replaced).
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Old 09-03-2015, 05:35 PM   #25
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Originally Posted by Al and Missy View Post
I'm not an electrician either, but I have done some NEC work. I believe you need only to size the wire for the highest capacity receptacle, i.e. 50A.

338.12B says USE shall not be used above ground except for transitioning to another cable type in an approved box.

I'm having trouble finding the voltage drop calculations, but I presume that is why you went to #2 as #6 would be good for 50A at 30 degrees C per the ampacity tables.

Al
I am looking first at ampacity (I started looking at the max for the box - 100A, but the NEC limits 2-2-4-6 AL to 90A for this application), but also voltage drop since it is a long run.
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Old 09-03-2015, 05:47 PM   #26
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I no nothing about electricity. I had a licensed electrician install a pedestal with a 50 and 30 amp plug. The run from the main panel was almost 200 feet and we used aluminum. This is how it looks, three boxes, one with breakers and the other two have the plugs. Works great. Didn't have an RV pedestal readily available, so took a different route.



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Old 09-03-2015, 05:50 PM   #27
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I am surprised you could not find a 30 amp pedestal, they seem to be at MANY campgrounds. If you plan on having people stay in your backyard next to your trailer I can see wiring for 50 amps, but if you are only running 30 amps, it is much easier. Breaker only draws from one side of the panel, no confusing wires.

I think technically if you do wire up the 50 amp you actually need a second run of wire for the 30 amp outlet. If you put a full draw on the 50 and ALSO put a draw on the 30 you would be overcapacity and run your wire hot until the breaker went. Same for the 20/15 amp outlet. If you are ignoring code and never intend to use more than one outlet label it so. There should be a lockout to prevent more than one working, but I don't know of any pedestal that supports a lockout, they just have the extra circuits run.

Aluminum is GREAT. Copper bends easier as it doesn't need to be as thick for the same rating, and it's generally a softer metal. But aluminum is LIGHT, and CHEAP. Don't diss aluminum, it's why there are metal airplanes instead of coated fabric.

-Randy
You can run a single (set of) wires (50A requires 2 hots). The breaker at the main box needs to be sized small enough to prevent over heating the wire (going above its rated ampacity) and large to avoid nuisance trips. It is complicated to calculate what is needed for a whole house (I assume most new houses don't go through detailed calculations - they just use 200A service and say it's more than enough). But, if you add up the amperage all of the circuits in your house, it will be more than the 100, 150, or 200A service because you don't max everything out at once. The important thing is that each breaker is sized to properly protect each gauge of wire.
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Old 09-03-2015, 05:50 PM   #28
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*I* would remember to not connect both the 50A and 30A, but the next guy might not know the limitation. So I would have to either put a 60A breaker off the main or get a 2 ga neutral.
Although I really can't imagine a situation where all 50a goes to just the X leg, and it just happens to be the same leg as the 30a plug, why don't you just run the neutral through a 60a breaker?
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