What size service wire for new workshop

[Cord]

If you want 125 amps of power at 3% voltage drop for a 125' in conduit using 220v you would need 1/0 in copper. To use a #4 copper wire you could still use the 125 amp panel, but would need to install a 70 amp breaker in the feeder panel. So you can actually go a bit bigger than the proposed 60a breaker. There is no need to use a smaller breaker in the sub panel as that main breaker is only serving as a disconnect.

 

[aczlan]

There is no need to use a smaller breaker in the sub panel as that main breaker is only serving as a disconnect.

As has been said, the only reason to downsize the main breaker in a subpanel would be if you wanted the breaker in the subpanel to trip before the breaker in the main panel (saving you from a trip back to the main panel).

Aaron Z

 

[747driver]

As has been said, the only reason to downsize the main breaker in a subpanel would be if you wanted the breaker in the subpanel to trip before the breaker in the main panel (saving you from a trip back to the main panel).

Aaron Z

Yes...that is one reason and the other is safety. I want that 50 amp breaker in the barn tripping, protecting the house main service.

 

[747driver]

Interesting. Lots of good advice. I always use aluminum URD. And direct bury it. Only place it goes in conduit is down the meter pole and up inside the building. I get it from my local electric company for about half of what box stores sell it for. 2-2-4(100a) is ~80 cents a foot and 4/0-4/0-2/0 (200a) is $1.50/ft. IF I ever have issues, I have a backhoe so its not hard to repair. But have never had issues, nor heard anyone have issues and there are/were alot of houses in my area serviced with URD direct bury over the last few decades.

As to a 12/2 or something for lights, I would say that is un-necessary. Get with the times. There are devices and Apps for that and would probably cost less than the added wire and switch.:thumbsup:

Going to get the wire today. Got 420 feet of #4 XHHW wire, copper. Its only .76 a foot. I am still somewhat old school...not into all those apps and gizmos ! Although i do have a Note 4 phone !! Everyone here has given me good advice...much appreciated !!

 

[LD1]

Yes...that is one reason and the other is safety. I want that 50 amp breaker in the barn tripping, protecting the house main service.

Your main breaker in the house will protect the house service. The only think your 60A breaker will be doing is protecting the wiring. You could make it an 80a/50a breaker combo and it would be no greater danger to the house service. IF you exceed its capacity, its own main breaker will trip.

 

[LD1]

Going to get the wire today. Got 420 feet of #4 XHHW wire,

If its truly a 120' run, you are gonna be about 60' short for the 4th leg

 

[buickanddeere]

Going to get the wire today. Got 420 feet of #4 XHHW wire, copper. Its only .76 a foot. I am still somewhat old school...not into all those apps and gizmos ! Although i do have a Note 4 phone !! Everyone here has given me good advice...much appreciated !!

120ft from house to barn. 420ft of wire? How does that work.

 

[sqdqo]

actually urd is not rated for conduit use. Use XHHW instead. Its also cheaper and rated for conduit.

URD is used in conduit all the time. It is direct burial rated but conduit provides an extra protection and a pathway for additional line voltage conductors of the same voltage class or replacement if necessary. Also I hope if your running that xhhw underground that its going in conduit. Xhhw is not direct burial rated. With copper wire you could have used thhn which is less expensive and has a wet rating and is permissible in conduit underground. Direct burial copper is called U.S.E.

 

[747driver]

URD is used in conduit all the time. It is direct burial rated but conduit provides an extra protection and a pathway for additional line voltage conductors of the same voltage class or replacement if necessary. Also I hope if your running that xhhw underground that its going in conduit. Xhhw is not direct burial rated. With copper wire you could have used thhn which is less expensive and has a wet rating and is permissible in conduit underground. Direct burial copper is called U.S.E.

Yes....the XHHW will be going in conduit. Its more suitable than the THHN for running in underground conduit. The XHHW was .06 cents more per foot.

 

[grsthegreat]

URD is used in conduit all the time. It is direct burial rated but conduit provides an extra protection and a pathway for additional line voltage conductors of the same voltage class or replacement if necessary. Also I hope if your running that xhhw underground that its going in conduit. Xhhw is not direct burial rated. With copper wire you could have used thhn which is less expensive and has a wet rating and is permissible in conduit underground. Direct burial copper is called U.S.E.

Urd loses its heat disapation in conduit, thats why we cant use it that way here in idaho. Its only allowed in pipe in the risers. We have to stick to XHHW if we want to go with pipe. Not surewhat other states allow.

There might be some confusion in terminology here. My supply houses sell what they call urd triplex and its rated differently than some types ive used in the past that carry other designations such as dual rated ser/urd or xhhw/urd, etc. ibelieve if i recall, some of these can be run in pipe.

Personally, pulling a twisted set of wires thru elbows sucks. Ill stick with the single xwwh runs. Way easier to pull.