trying to figure what wire to put in to feed the barn/shop.here’s the setup, 200 amp service to the house,subpanel out to the attached garage 60′ total,100 amp fed with 1 gauge alum. wire. now i need to set a sub panel off of that sub panel out to the barn which is 125′ away. i have a 100 amp panel in the barn,thought i’d just run more 1 gauge underground in 3″ conduit. went to get wire ,no one has #1 that is rated underground.#2 is rated for 100 amp,but this is getting to be a pretty long run so a little concerned with voltage loss. even though about the most i can see run at one time-20 amp saw,20 amp lights,30 amp air compressor,so if i max at 70amps the #2 would probably be ok. next option go to 1/0 alum wire and no i’m coverd no matter what, my concerns are first will the wire go into a 100 amp breaker and 2nd is cost.1.25 a ft and 3.00 a ft.whats your opinion on this????thanks larry
hand me the chainsaw, i need to trim the casing just a hair.
Replies
"#2 is rated for 100 amp"
No it is rated at 90 amps, if it and the terminations are rated at 75c.
The 100 amps (table 310-15b6) is for dwelling service cable, which this ain't.
http://www.csgnetwork.com/voltagedropcalc.html
Plugging in #1, 60 ft and 100 amps to the garage gives you a 1.1% voltage drop.
Using #2, 125ft and 70 amps give you an additional 2% drop.
So I would say install a 70 amp feed breaker and have at it.
ok,i've got to ask why when figuring the length you only use 1/2 of actual length?thanks larryhand me the chainsaw, i need to trim the casing just a hair.
The resistance is calculated on the total path length of the wire. In this case that is 250 ft (125 out and 125 back).But the calculator takes that into account and you only enter the direct distance as the crow flys (for arial) or as the worm crawls (for underground).