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cmaclean 01-14-2008 06:48 AM

Running Power to new Barn
Recently finished construction on horse barn in back yard of newly purchased home. All I require is in there is 3 fluoresent lights, 4 outlets, and 2 bulbs, and do not forsee needed anything more. From the main panel in the house, 2, 30amp breakers (60amps) feed a safety shut off box housing 2, 20 amp fuses. from there a line is buried underground outside to shed less than 100 ft away to another identicle shut off box wth 2, 20 amp fuses. all 10 Guage wire up until this point. All that is in this shed is one overhead fluor. light and a couple of plugs. Horse barn is less than 50 feet behind this shed. Can I run bury-able 12G off that second box in the shed to the horse barn and power the firstly mentioned items? Do I need another shut off box in the final detination...the horse barn? thanks for your time and help. Or what do you suggest?

J. V. 01-14-2008 10:50 AM

Possibly. What is the total distance from the main breaker at the house to the horse barn?

cmaclean 01-14-2008 11:02 AM

I'de have to measue to be 100% but safe to say less than 200 feet

Stubbie 01-14-2008 11:26 AM


From the main panel in the house, 2, 30amp breakers (60amps) feed a safety shut off box housing 2, 20 amp fuses.
If this is a 30 amp double pole breaker you do not have 60 amps you have 30 amps.

Is this one cable going to that shut-off box?

If so is it 10/3 G?...2 hots a neutral and a ground?

cmaclean 01-14-2008 12:11 PM


Stubbie 01-14-2008 01:43 PM

Ok .... tell me if I have this correct. You have 10/3 G cable ran from a 30 amp double pole breaker in the main panel to a 20 amp fused disconnect at your house. From that fused disconnect you have direct bury rated 10/3 G to another fused disconnect located at the shed. You want to go from the shed disconnect (shut-off) with a 20 amp feed to the barn to power lights and receptacles.

Which is closer to the house the the shed or the new barn? It sounds like the shed is inbetween the house and new barn? So the barn is 150 to 200 feet from the house main panel?

cmaclean 01-14-2008 04:42 PM are correct..shed is between house and horse barn...and total distance from house to horse barn is about 200 feet...

Stubbie 01-14-2008 09:16 PM

1 Attachment(s)
You should change the 30 amp breaker in the panel to a 20 amp double pole breaker. You may keep your disconnects at the house and shed. Just use a toggle switch for your disconnect in the new barn. This will remove several requirements from the NEC regarding seperate buildings. The direct bury cable needs to be 10/2 G from the junction box in the shed to the barn and should be buried 24". You may use 12/2 G to run your branch circuits in the shed and barn. The multiwire will be an advantage for voltage drop when you are operating loads in both detached buildings at the same time. Notice in the attached the JB in the shed you are going to split the circuit from the house. One leg (hot) of the multi wire will provide a 20 amp circuit for the shed and the other one will provide a 20 amp circuit for the barn. The neutral is shared between the branch circuits going to both buildings.. Any questions please ask.

cmaclean 01-15-2008 07:12 AM

Thanks fo the help and info....I will change that breaker...if the shut offs housing the 2, 20 amp fuses are rated at 30 amps....could I not have 30 amp fuses in them matching the breaker amp-age? or is 30 amps too much?

AllanJ 01-15-2008 09:42 AM

If you have breakers greater than 20 amps. protecting the "main line" out, then you must have a subpanel(s) at the shed and/or the barn with breakers no greater than 20 amps. protecting the branch circuits to the lights and receptacles.

You would need a ground rod at each building with a subpanel.

A 20 amp. feed (including a 20 amp. 240 volt shared neutral feed) from a different building does not need a subpanel at the destination.

Stubbie 01-15-2008 11:03 AM

What Allan has described is why I have suggested the design in the drawing and considering the loads you said would likely be used. I suppose since you have a 20 amp fused disconnect on the branch circuit going to the shed and it is located at the house you wouldn't necessarily need to change the 30 amp breaker in the main panel. But once you put 30 amp fuses in those disconnects a whole bunch of other requirements come into play as Allan stated. The double pole 30 amp breaker is rather unnecessary since the branch circuit lands on a 20 amp fused disconnect. This is why I suggested changing it out with a 20 amp double pole just to have a little consistancy. To use the 30 amp breaker effectively you would need a sub-panel in the shed as Allan mentioned. At any rate a 30 amp feed is rather an oddity anyway and isn't the choice you would want IMO if you are wanting more power at the buildings. With the loads you stated 20 amps in each building should be just fine. My personal opinion is a 60 amp feed is much more useful and will cover most any down the road additions. This would however entail more cost as the existing materials would all have to be replaced and new wire ran to handle the upgrade in power. As an added note 30 amps carried 200 feet would be borderline on 10 awg wire at a nominal voltage of 240 volts. So with what you have existing and expected loads and utilizing a 20 amp branch circuit on a multiwire single circuit feed is your most economical solution but not necessarily the best solution.

Also note there are many more things to consider with this installation than just what breakers and wire size are needed.

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