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#51008 - 04/18/05 06:45 PM 2-wire sub-panel???  
derater  Offline
Joined: Mar 2002
Posts: 179
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.

Work Gear for Electricians and the Trades

#51009 - 04/18/05 07:21 PM Re: 2-wire sub-panel???  
Tom  Offline
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
I swear, some people should just keep their hands in their pockets at all times & resist the urge to do electrical work.

I'm e-mailing you a handout on subpanels in separate buildings. It should cover what you need to know about grounding & bonding with the exception of the required bonding to the structural steel.


Few things are harder to put up with than the annoyance of a good example.

#51010 - 04/18/05 07:49 PM Re: 2-wire sub-panel???  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
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

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 a neutral to the panel. If in any doubt, it never hurts ti size it to the service the panel provides.

Two wires? Sure- if he only wants 120v.

#51011 - 04/19/05 06:39 PM Re: 2-wire sub-panel???  
derater  Offline
Joined: Mar 2002
Posts: 179
Well it is a 2 wire w/ noodle, but no ground.

#51012 - 04/19/05 07:18 PM Re: 2-wire sub-panel???  
e57  Offline
Joined: May 2003
Posts: 2,876
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.

[This message has been edited by e57 (edited 04-19-2005).]

Mark Heller
"Well - I oughta....." -Jackie Gleason

#51013 - 04/19/05 08:06 PM Re: 2-wire sub-panel???  
derater  Offline
Joined: Mar 2002
Posts: 179
Sorry if I wasn't clear- it is 2 ungrounded
and 1 grounded-but no GROUNDING wire.

#51014 - 04/19/05 08:24 PM Re: 2-wire sub-panel???  
BobH  Offline
Joined: Oct 2004
Posts: 135
Newfane, N.Y USA
Well that's alot different. I'm not clear what it is you're doing though. Are you rewiring the building that's fed with a 3 wire feeder? 2 hots and a grounded conductor. Is it conduit or cable?

[This message has been edited by BobH (edited 04-19-2005).]

#51015 - 04/19/05 09:05 PM Re: 2-wire sub-panel???  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
"Thinking outside of the code" ground....feed the damn place through a GFI breaker?

#51016 - 04/19/05 09:15 PM Re: 2-wire sub-panel???  
derater  Offline
Joined: Mar 2002
Posts: 179
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 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.

#51017 - 04/19/05 09:18 PM Re: 2-wire sub-panel???  
frenchelectrican  Offline
Joined: Feb 2003
Posts: 939
Wi/ Paris France { France for ...
let me ask this to make sure i understood this question.

is the building is a rental unit like rent a storage space or rent a garage ??

if this is a rental building it should have a electricican deal with this because the code is pretty strict with this and also is any water pipe or telephone wire there ??

if so you have to run full 4 wire set up.

Merci, Marc

P.S. make sure that building well gfci'ed

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

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