Dropped off 100a panel and some 3/0 on a spool at a friends.He's a mechanic, this project is a trade deal.In the mean time he rented adjacent(8')steel building out and someone ran 2/0 2-wire and powered the panel.What now? Ground rod and structure? and/or separate ground conductor back to main.And please explain the ground potential and other hazards with this install.
Now Tom, be nice....this is one area where the code stumbles around some. Why, just a few months back, the IAEI ((inspectors' org) asked three experts, and came up with four answers!
The article was in the Nov/Dec2003 issue of IAEA news, was called "# Chiefs come full circle on parallel paths and end on a tangent," and you should be able to read it at IAEI.org.
For a very simple summary of MY view.... The ground rod is for lightning protection. Every building gets one. The service is where the neutral and ground get separated...and stay separated. Every panel downstream get a ground wire sized to the current- and the ground rod at the other building gets bonded to this at the panel. And...I don't care how balanced your loads are, or if there is only 240v. equipment in that other building....run a neutral to the panel. If in any doubt, it never hurts ti size it to the service the panel provides.
OK thought about it, and theres something wrong here....
TWO WIRE PANEL?! Hot (1), neutral (1), thats it?
Fed with 2/0, or 3/0? Either way, next question is... how is the other side of the panel fed? Double lugged? From a 100A single pole breaker? One phase dead? Or is the only time I'll hear about a 120 only panel?
What will it take to get the other two conductors there.
Anyway, steel structure, no ground! With no fault path, a short circuit could kill someone coming out of the rain, and locking their hand around an energized door knob. Forget anything in regaurds to lightning, although also a hazard, it is more remote than the chances of other (in this case likely) electricution hazards. Like.... an HID, or flouresant fixture imposing 300-1200 volts on the metal surfaces of the building. Or, if someone, and it is likely here, that the nuetral is bonded to the panel can by the stupid screw that comes with them, that it is a parralel path for neutral current. A few minutes with a calculator with known loads, and I could give you an rough estimated amperage of a bare foot hippy leaning against the wall. (No offense to hippies who wear shoes.....)
If this is in conduit, yank out the the 2/0, or 3/0, and give it a #2 THHN feed, with 3-wires and a #6 ground. Or the other method described in 250.32 (Ground rod, neutral bond, AND bond the steel.) Depending if there is a metalic path between this shock chamber, and the main building.
Obviously I need to work on my communication skills.My understanding is sub-panels require 3-wire w/ground.In as much as the 2nd blg.is only 8' from the blg. w/ main panel (that feeds the sub), and it's steel(2nd. blg.).My concern is shock hazard.I wouldn't want to see my friend have legal problems and a clear explanation of what and why of what needs added (gnd. wire?)I had left the stuff there to do it right myself but someone jumped the gun.