Electrician Help! Wiring to RV Power Pedestal

[matthorr]

I just added a parking pad to my backyard to store my trailer. I am going to run full hookups out to it (for convenience and so it can be a guesthouse / AirBnB).

My question is for the electricians in the group - what is the appropriate wiring out to the power pedestal? My trailer is only 30A, but I have a 100A pedestal on its way (with one each 50A, 30A and 20A circuits). My wire run will be 65' in the ground, plus another 45' through a basement crawl space.

I'm getting confused looking at ampacity/voltage drop tables - do I need to use 100A in the tables, or 50A since that is what each of the two hot wires will carry.

My option A is to use 2-2-4-6 USE (Aluminum) Mobile Home Feeder. Is that large enough?

Another issue is USE needs to be in a conduit inside the house based on my understanding of the NEC. Is there an easier option (such as going right to a junction box inside the house and then using a wire type that does not need conduit through the house)? Suggestions on type of junction box / bus bar inside it / wire type?

I understand electricity, just not the NEC!!!

Thanks.

[dbj216]

I'm going to bump this thread to the front of the line as I think you have an interesting question. We need an electrician Airstreamer to help out.

I ran a 30 amp circuit to my trailer pad. We had the house wired for a 30 amp RV connection when it was built. I simply ran outdoor conductor underground about 25 feet and wired it to a 30 amp receptacle. It was a much easier job than you are undertaking.

I think your trailer will make a great Airbnb location. It will be a lot more interesting than a Super 8.

David

[nrgtrakr]

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.

[jdalrymple]

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.


Regards,


JD

[lewster]

The only comments I can make to this thread are:

• Retain the services of a licensed local electrician who is not only familiar with NEC, but also local electrical requirements

• I wouldn't use aluminum if you gave it to me for free

• I would have ALL conductors the same gauge. This is a requirement on marine wiring, and IMHO, should be followed on ANY wiring project! Minimal gauge neutrals and especially grounds are a recipe for problems. I would never use anything else for myself or my clients.

[nrgtrakr]

When I remember the hospital renovations, the wire was always the same gauge. I wonder why the code changes?
Give me Lewster's aluminum wire, I'll take it to recycle, buy copper.
Some places will let the property owner do their own work, but you still need a permit and pass inspections.
Now where is that electrician?

[Hiho Silver]

Originally Posted by lewster

The only comments I can make to this thread are:



• Retain the services of a licensed local electrician who is not only familiar with NEC, but also local electrical requirements



• I wouldn't use aluminum if you gave it to me for free



• I would have ALL conductors the same gauge. This is a requirement on marine wiring, and IMHO, should be followed on ANY wiring project! Minimal gauge neutrals and especially grounds are a recipe for problems. I would never use anything else for myself or my clients.

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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[kennethowens]

#6 Awg COPPER has 0.3951 Ohms per 1000ft

you are using 1/10th of 1000ft

at 30 amps usage...Volts=Amps X Ohms

V=30A X .03951Ohms = 1.1853 Volts dropped along 100ft

That is less than 1% of 120Volts

It will work.

Electricians onboard?

[Al and Missy]

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

[kennethowens]

You wrestle a #2 wire awhile...write back about the experience.
Stiff bugger will KICK YO BOOOOO-DEE
Try it
Ol #6 aint no punk
Refer to the calcs above

[kennethowens]

You wrestle a #2 wire awhile...write back about the experience.
Stiff bugger will KICK YO BOOOOO-DEE
Try it
Ol #6 aint no punk
Refer to the calcs above

[dznf0g]

Heck, I wrestled 6ga through conduit in the basement and up the outside of the house and that was bad enough. It was over kill for a 45' run, but the supply house was out of 8ga and I was impatient. It was only a 30 amp circuit.

[israndy]

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

[nrgtrakr]

If it were me, I'd send the 100 amp box back, get a 30 amp box and run wire accordingly - much cheaper, easier.
Where is that electrician?

[markdoane]

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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[greghoro]

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.


Greg

[greghoro]

Originally Posted by israndy

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.


Greg

[Al and Missy]

Originally Posted by israndy

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.

....

-Randy

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.

Al

[greghoro]

Matthorr - much speculation in assisting you can be put to rest if we knew exactly what pedistal you purchased.

Manufacturer and model, please.


Greg

[joemikeb]

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.