Pole barn sub panel
- Thread starter bearcreek paul
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mx842
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Hey what is 300 mcm? that is what it says I need for my barn.
grsthegreat
Super Star Member
Yeiks...thats some spendy wire. How many feet you going to need. I ran 350 MCM to my shop, but the run was 350 feet and I'm using 200 amps. I did this about 4 years ago, and it was expensive back then. Currently its running $1.35 per foot for each run. You would need 2 runs of this and a downsized neutral (250 MCM) run Plus a #6 ground. I personally run my neutral the same size as the main conductors, but you can drop it to the next size down.
I ran 3-1/2" conduit for ease of installation, as it is legal to go 3" but a pain to pull in it. You'll not find this wire at Home Depot....best locate an electrical wholesale house nearby.
What distance are you looking to run, and what amperage
A better calculator to use would be this one
http://www.csgnetwork.com/voltagedropcalc.html
It allows you to adjust for voltage drop. For me if i used the previous posters calculator i would have needed to use 500 MCM wire, but i allowed myself a 3% voltage drop (acceptable) and only needed to use 350 MCM wire using this calculator or the formulas in my NEC book.
By the way, they figure a circuit as a loop (up and back) so the figure for 1/2 the circuit distance means the length from the main panel to the sub panel - one direction
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Danno1
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rambler
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The ground rod is still a good idea/ allowed correct?
Sure woulda used one size bigger wire, would be nicer to the electric motors in a shop setting....
That box has enough spaces that it does require a main breaker in it - which will take 2 of your spaces away.....
Main feed needs the pipe.
As well, the wire leading away needs a staple within 8 inches of the box, would not appear to be there tho not sure.
--->Paul
grsthegreat
Super Star Member
you DO need a single ground rod per 2008 and 2011 code book for a panel in a separate building. Also need the 4 wire run from main panel to subpanel, and yes a main breaker is required in a separate buildings panel.
mx842
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Thanks, My service to my house is 400 amps and I plan on splitting that service and making each location 200 amps. I have a concrete slab blocking me from dropping down and coming straight out of the service feed at the house and the way I had planned to run it would be 300 ft or maybe more. I have not measured it out there yet but now I am thinking I will tear out that one pad and run it that way and I can save at least 100'. I can pour another concrete slab cheaper that I can buy the wire for.
I had heard from an electrician buddy that I didn't have to worry much about voltage drop until I went 250' or more if copper is used. I was at Lowes the other day and their chart says I needed 1/0 copper for 200 amp service and I almost passed out when I figured out what I needed would cost. Now I find out I need to go bigger and the way it looks I'll have more in the wire than I do in the lumber so far.
Thanks bearcreek paul for making this thread cause it made me think about what I would need to do about my electric service as I reached that point. I'm still a ways away before I need to buy the wire and this thread made me realize how nice I need to be to the wife over the next month or so to be able to shell out the clams for this part of the project.LOL
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You don't use copper on service or sub service feeders. Aluminum is 1/4 the cost. You wont find that at the box stores, you'll have to go to an electrical supply company.
Without looking it up that is what I would have come up with. I put a service in my new pole barn a few weeks back and I needed a local ground rod. Years ago I don't believe it would have been a requirement.
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grsthegreat
Super Star Member
DONT USE OPPER.... youll bankrupt yourself. I dont know of a single contractor that will use copper feeder for residential service. If you can cut it down to 200 feet, then 4/0 aluminum wire will gove you only a 2.8% voltage drop, which is acceptable. You can easily but 4/0-4/0-2/0 URD direct burial wire and also a #6 alum XHHW ground wire and either bury that mess 24" below the surface or install it in 2" schedule 40 PVC conduit (i highly recommend) and go 18" below the surface. You would actually need 2/0 COPPER to meet the requirements for 200 amps and this would allow for a 3.1% voltage drop.
