What guage wire to use???

[FATCAT]

I need to run underground, a wire to my shed for my Kubota tractor (to keep it warm this winter), and to have a light. I am looking at installing just one 15amp outlet in the shed, but the shed is 250 feet from my house ... so, would I need 10/2 UF or could I get away with 12/2 UF (or do I need 8/2 UF)?

 

[Gray Ghost]

Fatcat

My book says

14 guage 15a with a 3. 7v drop per 100ft

12 guage 20a with a 3. 1v drop per 100ft

10 guage 30a with a 2. 9v drop per 100ft

I personally would use12g and a 20 a circuit.

Never know when I want to use the circuit temp for something else.

 

[KBennett]

I assume the heater for the Kubota is less than 1000 watts and if that is the case the 12 gauge should be fine.



If there are any motors (fans, compressors, etc. ) I would go with the 10 gauge. Motors don't last very long if you don't give them full voltage.

 

[FATCAT]

Nope, no motors to start, just a block heater for the winter and a light that will hang from the shed roof.



Thanks ... I'll go with 12g

 

[klenger]

I agree on the 12 ga. You only need 14 ga for a 15 amp circuit, so you are already oversized.

 

[PJereb]

Your tractor heater probably draws a fair amount of current (10 amps?). If you are going through all that work to trench and run wire 250 feet I would error on the cautious side. If I was going to do the same thing I would run 10-3 (because of the distance) and use a couple single pole 20 amp breakers, that way you have two separate 120V 20 amp circuits for your shed. That should be more than enough to run a block heater, a small space heater and a few lights. It would only cost you an extra $50 bucks, and would probably pay off some time in the future when you need more juice in your shed.



Peter

 

[mike r]

Run the 10guage UF wire with one 20 amp circuit breaker, NOT TWO circuit breakers! A 1000 watt block heater will incur additional voltage drop when in service, the 3 volt drop per 100 ft is a non current carrying rate. The third wire in the 2 wire and ground is not insulated and is NOT a current carrying wire and not to be used for that. If you wish to run two distinct circuits you MUST use 3 wire plus ground. If you do run 2 circuits with the 3-wire and ground you must use a 220 volt circuit breaker so that if you choose to work on one circuit, the other circuit utilizing the same common nuetral will also be deenergized simultaneously. Little extra money but its safe.

 

[MGordon]

Assuminig a 10 amp load, voltage drop with 12 gauge is 9. 65 volts, 10 gauge is 6. 05 volts.



The National Electrical Code recomends keeping voltage drop to 3%, which would require 8 gauge wire, thus a 3. 24% drop.



All that being said, I would probably use 10 gauge because the type of load you have is not voltage sensitve.

 

[dresslered]

It seems like everyone is giving you accurate sizing for the ratings, but if it were me, the trench is the hardest part. I would drop 6/3 down there and never worry about loading limitations again. I might even think about adding additonal wiring for a remote switch, sprinkler control, water line, etc.



You come to my house and dig the trenches, and I'll go to your house and do the wiring. :-laf



Also, direct burial wire should not be run inside of conduit. This limits its ability to cool.