Is there an electrician in the house?
 

I need some help.

I want to install a 30A receptacle on the outside of my house in a weathertight box. Do I need conduit from the breaker box to the receptacle or can I just run the wire? And what size conductor do I need for that application? The wires will be exposed to the outside. The load will not exceed 30A but will vary.

Thanks

yes yes and 8 gauge or larger

Exposed outside should be "direct burial" wire.

Bruce, it's not buried but under the (raised) house.

The load uses 10 ga wires if that changes anything zip.

I want to plug in my trailer at home so I can use it in case the a/c dies on me and also as an extra office.

If it's up under the house, it's not "exposed to outside", but if it sees any weather it should be direct burial.

If the wire is exposed, then it must be in conduit (or some protective enclosure). IOW wire on a house side must be in conduit. Someone could touch it. Some moving items could strike it. Wire inside the wall cannot be touched - is protected. No conduit required.

Wires through or between floor joists beneath the house are considered not exposed. Considered protected from human contact. No conduit necessary as long as it runs along joists or on the plate that joists sit on.

I cannot say enough about anchoring a weather tight box so that no moisture gets behind it. Whenever possible, I cut the plywood and mount that box partially in the wall - mounted firmly to a 2x4 nailed between two studs. Just mounting the box attached to plywood by screws is (by my standards) woefully insufficient. It must be firmly anchored (if possible) to wall studs due to the 'violence' imposed by plugs - especially 30 amp plugs.

I believe this outlet must be powered by a GFCI breaker. I don't know of any exception.

TW, thank you for that post, it was very good! It is duly noted that you did not mention the phrases "mental midget" or "corporate bean-counters" or even the word "innovation".

I think I will use conduit anyway, just because it is cheap. I can anchor that to the floor joists easily and access the underside of the mobile home easily. Getting the wire through the walls will be trickier as it isn't drywall but that cheap paneling-like wall material that is so hard to patch. A GFCI goes without question for an outdoor appliance. The box is a little tough to securely mount due to the lack of 2x4s. I think I can make a secure mount point between the joists though. I know enough to seal the box with silicone sealant at the wall.

Zippy mentioned 8 gauge wire. There is a significant jump in price between 10 and 8 gauge wire. Since the appliance cord uses 10 gauge, may I assume that keeping that size back to the breaker is kosher?

Thanks again

Bruce, I believe the NEC specifies that outdoor means anything that is not indoor. There can still be moisture under there, temperature is a factor also. Not to mention mice, bats, insects etc that might damage the sheathing. I will have to consult with a pro on the exact type of wire needed. Maybe armored cable due to the pass through the floor, maybe UF is ok or since I think I will use PVC conduit, type TW.

Direct burial is not needed, else I would use aluminum conduit. Burying the wire would be nice except I would need a pro to dig the trench due to the presence of many tree roots. Further, since this is a mobile home, a buried wire is not desired.

Direct burial need not be buried, but withstand all the elements can throw at it. Chewing critters is another matter.

Our local code says it still should be in conduit if it is not buried, I think. We had some work done on our hot tube and all the wire that runs to it is in conduit. I would think for safety you would need to do the same to prevent animals from eating the wire. But I assure you I am no electrician.

When In Doubt run conduit ,

yes there is a difference in 8 and 10 gauge wire
But the thicker the conductor the less resistance , thus the Less heat

Oh And I agree with TW about finding some thing Solid to Mount the Box to

"Yes there is a difference in 8 and 10 gauge wire
But the thicker the conductor the less resistance , thus the Less heat."
Resistance is inversely proportion to wire size, also length is to be figured in. IIRC.

FWIW. People buy the 16 Ga. ext cords and wonder why their drills and such burn up.

I would change the way you're doing this. The trailer spec's will tell you what current it should be given.

Typically 20A for "just getting by", and up to 50A for full capacity.

They sell trailer hook up cables which are sized for your trailer's needs, at the trailer or RV supply houses. The cables are quite long, and quite heavy. They're made to simply lay on the ground between the power outlet (a heavy duty 3 or 4 prong appliance type), and the utility hook up site on the trailer.

I've been using one of these for my trailer for 10 years, with either 20A or 50A sockets. (two sets of cables). No problems whatsoever.

The power outlet on the side of the house, should be about 3 feet above the ground level. Any higher and the weight of the cable will pull heavily upon it. You want a thorough rain "roof" over the power outlet, with heavy duty breakers right next to it. Visit a local RV park and see how it's done with their power "pylons".

The advantage is that your cables will be sized right for the trailer, and the cables can be stored in the trailer at any time , making it entirely mobile.

The laying on the ground mode, has worked well despite being in an area that does have some rats. They don't chew on it. :) I suspect a lawnmower might be the bigger hazard.

Adak, I got that part covered. It's the connection at the house that I need to add. My trailer requires 30 amp 120 volt power. Only. My house doesn't have this outlet, which is why I need to add one. Running an extension cord from the house to the trailer is the easy part. My biggest hazard is not the mower but the DOGS! They chew through ANYTHING! Just ask my air conditioning repair guy! They ate through the lines to the condenser. I will be hanging the cord up high so they can't get at it.

Length of the wire from the circuit box to the outlet is about 16 feet. I'm also not sure if I need to add a sub-panel for this. I do believe I should just hire a local electrician and save myself all the bother.

Y'know B, I mean this in a positive way, but if you live in a trailer and drive for a living and your dogs eat the lines to your AC condenser...

...you might be a redneck