300 ft. underground feed to cabin

Customer has a cabin on their property about 300 feet from their shop. They want power to the cabin, just enough for a couple of lights and plugs. Can this be done without a subpanel in the cabin? My experience is with running underground feeders to subpanels, but for this I’m thinking a breaker in the shop and a 2-conductor + ground direct burial romex feed to the cabin. I assume that for 300 feet I would have to derate the wire and maybe use 10 gauge or even heavier if I want a 20 amp breaker.
My electrician will do this, and it will be on permit and inspected–I’m just looking for some info to chew on this weekend while doing some estimating for them. Sparky will not be answering the phone over the weekend…. smart guy.
Replies
You can run a "single circuit" to an outbuilding. Otherwise you need a sub-panel.
Sometimes (depending on AHJ) you can run a multi-wire circuit (basically a 240/120 circuit on a 2 pole breaker) to give you the eqivalent of 2 120 circuits.
The problem is that at 300 ft to get a 3% voltage drop at 20 amps then you need #4 wire.
It might be better to run 240 at 10 amps and then have a transformer at the other end. That would allow you to use #10 wire.
http://www.electrician.com/vd_calculator.html
You might want to get the electrican on this up front to see what your options are (and what the AHJ will accept).
What types of appliances do they plan to run in the cabin? I'd be very concerned about line loss and the resulting voltage drop. My house is about 400 feet from the road, and our hydro company told me I'd have about 70 to 80 volts if I where to put the transformer out at the road (we didn't). This can be very hard on motors and some electronics.
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
No appliances, just lighting probably, and maybe a clock radio or something like that. It's a 12x12 cabin with a small loft, to be used as a guest room.
I'm going to look into both possibilities that Bill mentioned. For now the electrical component is going into the estimate fairly high.
Edited 2/25/2006 9:56 am by davidmeiland
For what you mentioned you could probably figure it based on 5 amps or so.HOWEVER, someone will end up plugging in a saw or drill someday and not only will the ligths dim, but the motor will burn out.Or want to stick in a microwave or "dorm" refigerator.
Phase 1--run power to the cabin
Phase 2--I remodel the cabin, and I don't like listening to a generator.
I'd rather run a solid 20 amps out there. If they want someone to throw in a piece of 12/2 UF that's 300 feet long then they need to get someone else.