Question for an Electrician

[dwain]

I am going to run about 150 feet of buried electric wire to a small pole barn. I will have 3 or 4 lights, and about 6 110 volt receptacles. No heavy duty work on the outlets, will use mainly for lighting. What size and type wire would you think I need to use to feed the building?

 

[Ericpwp]

I got #8 for 15 amps. Not an electrician.

http://www.southwire.com/support/voltage-drop-calculator.htm

 

[hoosierdoc]

overbuild it, overbuild it. Never know when your hobbies will change. If you have room on the panel, run lots of power IMO

 

[bulletsmith]

I got #8 for 15 amps. Not an electrician.

Voltage Drop Calculator

Unfortunately, this is correct.

You might as well buy a 3 conductor (with ground) and install a little 30 amp sub panel out there. You can use #8 wire at 240v (two hots and a neutral ). This gives you a little more power and a few more choices down the road.

 

[1911ly]

12 gauge will do nicely. 14 would be fine even. I'd go 12. Heaver wire is always a good ideal. 8 gauge, would be around 40 amps. Over kill for lights and a few outlets.

 

[russc2542]

I also agree with overbuilding to account for deterioration over time and future expansion. There are still too many unknowns to be sure anyway. 14 works if you don't mind filling your pool through a coffee stirrer straw or only have 1-2 incandescent drop lights that don't care if you're only running 105v out of 120. Burial of the wire also affects it's capacity.

OP, you also need to sit down and figure out how big of a space you want to light, how well lit (are we talking garden shed where you need enough to not fall on a pitch fork or hobby area that needs clinical lighting?) and how you want to light it (incandescent, CFL, tubes, LEDs, HIDs?). I mean, about 3-bays worth of my garage is lit by a pair of screw in light sockets with 2 100w equivalent CFLs each, that's the daily driver parking side. A bay and a half of the "working" side has a dozen 4-tube flourescant fixtures, a few 2-tube fixtures, and some screw-in sockets. I pull about 8 amps @ 240v on that side. It's not quite as bright as a hospital...

 

[eldirector]

As mentioned above, I'd go with a small (30A) subpanel in the barn, so 8-gauge 3-conductor wire. Beats running 150' back to the house when you need to kill power in a hurry. Let's you add/remove circuits more easily as well.

Heck, I just ran the calc above both ways (30A 220V and 15A 110V) and it says 8-Gauge. So.... There you go.

 

[CountryBoy19]

12 gauge will do nicely. 14 would be fine even. I'd go 12. Heaver wire is always a good ideal. 8 gauge, would be around 40 amps. Over kill for lights and a few outlets.

Length of run is part of the calculation, heavier wire for longer runs...

 

[Ericpwp]

Yes, internal resistance of the wire will drop voltage and you won't have what you think you should have at the end of the run.

You can see it in action when you try to turn on an air compressor or something with a long under-sized extension cord. Nothing happens. You take the cord out of the equation and starts right up.

 

[Fargo]

I am going to run about 150 feet of buried electric wire to a small pole barn. I will have 3 or 4 lights, and about 6 110 volt receptacles. No heavy duty work on the outlets, will use mainly for lighting. What size and type wire would you think I need to use to feed the building?

Unless you are running conduit, you need something with a sheath rated for direct burial. To do it properly, you really need to put a small subpanel in the pole barn, they are cheap at lowes. Code will also probably want a new ground out there as well. I would run a 30 or 40 amp service and then wire the barn with Romex.

I would never run 12 or 14 for a distance like that unless I only needed one outlet. You need to have little enough resistance that you actually have a usable service at the other end. Undersize it and you will be kicking your feeder breaker every time you turn something on.

Use a voltage calculator to determine what gauge you need. The 8 others have referenced sounds right but I haven't run the numbers myself.

 

[nbunga]

Whichever wire size you go with make sure you buy it at an electrical supply house vs. Lowe's or Menards. I ran 200' of new wire to my well last summer and it cost less than half of what the big box stores charged. Plus you can buy it by the foot. All-phase is where I think I got mine. They have multiple locations in Indiana I believe.