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kavik001 09-10-2007 11:29 AM

help running electricity to barn
 
I recently put in a 10/2 wire underground to a barn about 330 feet away from the main panel. Now I am trying to figure the best way to hook it up. I think I have 2 options:

1) run it 120 from the main box with either a 20 or 30 (??? help??) amp breaker to the barn directly to a gfi recepticle and run a switch for a fan/light setup off that. I think that will protect everything.

2) Can I run it 220 with the 10/2 wire to a small panel in the barn, and use the one wire for neutral then ground the box w/ a ground rod? Then run the individual circuts (plug, fan, light) off individual breakers)?Will this provide me advantages in regards to available power and amount ? I probalbly will not be using 220 at the barn. If I went the 220 route would I use 20 amp breakers from the main panel or 30?

Make any sense?

J. V. 09-10-2007 01:24 PM

10/2 wire is a maximum 30 amp breaker. You need 10/3 for 220 volt plus neutral. You can get 220 volts with 10/2 but it will not have a neutral. You cannot use the bare copper wire as a neutral either.
To set a sub panel at the barn you actually need 4 wires. Two hots, One Neutral and one ground. The neutral and ground must be seperated. You will also need one or two ground rods.

Consider this a 120 volt branch circuit as in any other circuit in your house. You can mount a small 30 amp disconnect/switch in the barn to enable you to bring wires out for recepts and other small loads.

330 feet is a long ways from your house. I would be concerned about voltage drop at the barn.

elkangorito 09-10-2007 01:58 PM

Quote:

Originally Posted by J. V. (Post 62246)
....330 feet is a long ways from your house. I would be concerned about voltage drop at the barn.

I totally agree with J.V. on this. Actually, I guarantee that the size of the cable will need to be upgraded to deal with the inevitable voltage drop. I would do this calculation before purchasing any cable.

HouseHelper 09-10-2007 02:08 PM

All you can do with the 10/2 already in place is have a single 120V circuit. Protect this with a 15A breaker and be aware that once you pull a load in excess of about 6A, voltage drop will be an issue. In other words, lights and a ceiling fan will be just fine, table saws and other large motors will not be.

elkangorito 09-10-2007 02:16 PM

Quote:

Originally Posted by HouseHelper (Post 62262)
All you can do with the 10/2 already in place is have a single 120V circuit. Protect this with a 15A breaker and be aware that once you pull a load in excess of about 6A, voltage drop will be an issue. In other words, lights and a ceiling fan will be just fine, table saws and other large motors will not be.

Could you please help me to understand something? What is 10/2? I'm an Australian & as such, I'm only familiar with the metric S.I. system.

HouseHelper 09-10-2007 03:08 PM

Quote:

Originally Posted by elkangorito (Post 62264)
Could you please help me to understand something? What is 10/2? I'm an Australian & as such, I'm only familiar with the metric S.I. system.

US terminology for #10 American Wire Gauge (AWG) cable with two conductors plus a ground. A solid #10AWG wire has area of 5.261 sqmm and a diameter of 2.588mm.
That help?

kavik001 09-10-2007 03:21 PM

OK, so should I use a 30 amp breaker off the main panel to help account for some voltage drop or 20 amp?

HouseHelper 09-10-2007 04:09 PM

Quote:

Originally Posted by kavik001 (Post 62276)
OK, so should I use a 30 amp breaker off the main panel to help account for some voltage drop or 20 amp?

Use a 15A as stated earlier.

elkangorito 09-10-2007 04:24 PM

Quote:

Originally Posted by HouseHelper (Post 62272)
US terminology for #10 American Wire Gauge (AWG) cable with two conductors plus a ground. A solid #10AWG wire has area of 5.261 sqmm and a diameter of 2.588mm.
That help?

Thanks...it does. I'm sure glad the metric system is easier. All metric wire sizes are in square millimetres to one decimal place. E.g. power cable is 2.5 square millimetres & rated at 20 Amps continuous if it is in Thermoplastic Shielding & installed in a location where the ambient temperature does not exceed 40 degrees Celsius.

elkangorito 09-10-2007 04:27 PM

Quote:

Originally Posted by kavik001 (Post 62276)
OK, so should I use a 30 amp breaker off the main panel to help account for some voltage drop or 20 amp?

Changing the size of the circuit breaker will in no way affect the voltage drop. You should do a voltage drop calculation to find out exactly how much current you can draw through the cable before the voltage at the end drops by more than 5% of the supply voltage.

As a general rule, a voltage drop of no more than 5% is acceptable for most equipment/situations.

HouseHelper 09-10-2007 04:45 PM

I recommend the 15A breaker because once the draw is much more than 6-7A, voltage drop will be an issue, so best to protect whatever he is trying to run with the lowest rated breaker available.


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