I have a friend who built a 25x30 metal building. He is wanting electric ran to his building from his main panel located approx. 160 feet away in his main residence. He is pretty much just wanting some lights and recepts. along with a receptacle for a window a/c unit. I believe the load on the a/c unit will be around 15 amps max probably less and his lighting and receptacle load will be minimum. I am going to size his feeder for 60amps max. continuous. I have performed some voltage drop calculations and due to the distance, I have come up with #2 awg feeder size at a maximum continuous load of 60 amps with no more than 3% voltage drop on the 120V side. I am looking for some confirmation from anyone else who may read this. Please advise. Thanks!
Subpanel feed to shop building.
- Thread starter jchelm24
- Start date
- Status
I come up with #4 CU or #2 AL
(using this from Mike free-stuff)
http://www.mikeholt.com/documents/freestuff/other/VoltageDropCalculator.xls
(using this from Mike free-stuff)
http://www.mikeholt.com/documents/freestuff/other/VoltageDropCalculator.xls
Last edited:
Why are you sizing so huge? It is doubtful that he will have a 60A unbalanced load.
It sounds like a 20A multiwire branch circuit on 8-3 would probably meet his current needs if the AC was on one leg and the lights/receptacles on the other.
Going to a 40A feeder would give him a lot of extra capacity. A 50A or 60A feeder (breaker size) seems plenty, on #6 cu or #4 cu.
I'd also encourage a small 240V AC unit if the homeowner is up for that and you run a feeder.
It sounds like a 20A multiwire branch circuit on 8-3 would probably meet his current needs if the AC was on one leg and the lights/receptacles on the other.
Going to a 40A feeder would give him a lot of extra capacity. A 50A or 60A feeder (breaker size) seems plenty, on #6 cu or #4 cu.
I'd also encourage a small 240V AC unit if the homeowner is up for that and you run a feeder.
note: my error, it would be a #2 cu (I figured at 240v)
I agree, I would probably go 240/120 if I was installing the feeder and most likely figure a lesser load but, according to Mike's formula, you are correct with a #2 for 3% at 120v.
I agree, I would probably go 240/120 if I was installing the feeder and most likely figure a lesser load but, according to Mike's formula, you are correct with a #2 for 3% at 120v.
I know I am sizing large, but as with all shops, you think you only need a few amps until you start adding stuff like welders and such. I'm just looking out for my buddies best interest in the future. The cost isn't that much different between wiring it for 40 amps and wiring it for 60. Thanks for the replies. I just wanted to confirm the calculation. Thanks again!
- Status