Barn subpanel wiring

WEgyptAugust 16, 2013

I know 4 wires are required for subpanel wiring 2 hot, 1 neutral and 1 ground. I also know that the ground bus and neutral bus are to be isolated at the subpanel which makes sense if you have the 4 wires from the main panel. But I have never heard an explanation as to why you cannot wire the subpanel in a way similar to the main panel, with 2 hot from the main panel with no neutral or ground from main. The subpanel would have neutral and ground on connected bus bars but separate from the main panel. I know that this works and apparently without problems because I have seen this in several older barns and outbuildings in my area.

Thank you for reporting this comment. Undo
wirenut1110

Where do you propose to get this " neutral and ground on connected bus bars but separate from the main panel." from, if not the main panel?

    Bookmark   August 16, 2013 at 1:36PM
Thank you for reporting this comment. Undo
WEgypt

The one I was looking at has a separate ground rod for the subpanel and the neutral and ground wires for the outlets were connected to ground bus in subpanel.

    Bookmark   August 16, 2013 at 2:22PM
Thank you for reporting this comment. Undo
WEgypt

The one I was looking at has a separate ground rod for the subpanel and the neutral and ground wires for the outlets were connected to ground bus in subpanel.

    Bookmark   August 16, 2013 at 2:23PM
Thank you for reporting this comment. Undo
wirenut1110

Oh MY God!!!! You've got to be kidding....please tell me you are joking!!!

    Bookmark   August 16, 2013 at 2:58PM
Thank you for reporting this comment. Undo
jreagan_gw

You really want both the neutral and ground to go back to the main panel AND you'll want one or two ground rods at the barn. Don't do anything less than that.

    Bookmark   August 16, 2013 at 9:56PM
Thank you for reporting this comment. Undo
petey_racer

First off, a ground rod has NOTHING to do with the ground wires going to the receptacles and outlets. Ground rods serve a COMPLETELY different purpose.
Anyone attempting to use a ground rod as an equipment ground will be in for a surprise.

Older sub-panels to detached structures were allowed to be wired like main panels. IE: two hots and a NEUTRAL. The neutral also served the purpose of the equipment ground. Thing is, if there is an open in the neutral circuit there is the very real possibility that the panel box and anything metallic in the system could become live with voltage since the neutral is a current carrying conductor.

    Bookmark   August 17, 2013 at 7:51AM
Thank you for reporting this comment. Undo
wirenut1110

Petey, he's talking about using ground rods for neutral and ground.

[QUOTE]with 2 hot from the main panel with no neutral or ground from main[/QUOTE]

    Bookmark   August 17, 2013 at 8:27AM
Thank you for reporting this comment. Undo
petey_racer

"Petey, he's talking about using ground rods for neutral and ground.

[QUOTE]with 2 hot from the main panel with no neutral or ground from main[/QUOTE]"

Right. Which make it 100X worse.

    Bookmark   August 17, 2013 at 8:57AM
Thank you for reporting this comment. Undo
Stevie51

In a sub-panel the neutral wires are mounted on one bar that is mounted on plastic insulators so that it will not bond with the enclosure. This is refer to as "floating the neutral wires". This step alone has created only one pathway for neutral currents to travel to the main panel (we want only one pathway for neutral currents). Because current flowing through a wire create an impedance in that wire, this neutral pathway is also called a high impedance pathway. When a short circuit fault occurs between a hot wire and a enclosure, the fault current must have a separate low impedance pathway to the main panel in order for the circuit breaker to function quickly. The equipment grounding conductor provides this low impedance pathway. The equipment grounding conductor is connected on a separate bar in the sub-panel that is not insulated from the enclosure.

    Bookmark   August 18, 2013 at 2:01PM
Thank you for reporting this comment. Undo
Stevie51

Truth of the matter, whether you or the NEC like it or not, the power company is only going to provide your resident with 3 wires from the secondary side of the pole mounted step-down transformer (240 volts single phase with a center tap neutral). We are faced with no other alternative but to use the neutral wire coming from the transformer into the panel that contains the first disconnect (main breaker) to carry both the neutral currents and the ground fault currents. This is why your main circuit breaker panel must have the neutral wires, earth ground connection and equipment grounding conductors bonded together in that panel.

    Bookmark   August 21, 2013 at 9:13PM
Thank you for reporting this comment. Undo
Ron Natalie

However Stevie, the original poster asked about not having ANY grounded conductor.

    Bookmark   August 22, 2013 at 8:19AM
Thank you for reporting this comment. Undo
btharmy

I hope the OP understands, just because he saw an installation one time in an old barn, doesn't make it right, legal or safe. Sounds like a death trap to me.

    Bookmark   August 22, 2013 at 4:00PM
Thank you for reporting this comment. Undo
Stevie51

[Quote] "The one I was looking at has a separate ground rod for the subpanel and the neutral and ground wires for the outlets were connected to ground bus in subpanel". Sounds to me WEgypt is describing a 3 wires fed sub-panel in a detached structure which was very popular in older barns and outbuildings in rural areas prior to 2008.

    Bookmark   August 23, 2013 at 8:15PM
Thank you for reporting this comment. Undo
Ron Natalie

No Stevie, he says "no neutral or ground." This is not nor never has been a safe nor legal way of doing things. Three wire hook ups were legal up until recent versions of the code provided there were no OTHER metallic paths (either electrical or for other system) between the structures. The why for that has already been explained by petey.

    Bookmark   August 23, 2013 at 9:02PM
Thank you for reporting this comment. Undo
Stevie51

[Quote] No Stevie, he says "no neutral or ground." Well Gee Willikers that would be considered as being one step ahead of the Amish (as opposed to not having any electricity), and being one step closer to seeing God. The load on one hot bus bar will connect in series to the load on the other hot bus bar when attempting to use the branch circuits wired to the neutral/ground bar. The problem is ...if the loads isn't kept balanced (equal) between the two hot bus bars, the voltage will be different (more than 120 volts some branch circuits, and less than 120 volts on other branch circuits).

    Bookmark   August 24, 2013 at 4:04PM
Sign Up to comment
More Discussions
Does a refrigerator need to be on a separate circuit?
Does a refrigerator need to be on a separate circuit?...
rontero
Spa Capacitor question
My spa is wired for 220v. The pump motor is rated for...
pugmark
Looking for Ideas For Lighting at base of 300' long driveway
Sorry for the "picture through the screen"...
dixieman
Replacing fan speed dial back to standard toggle?
I am removing a ceiling fan and replacing it with a...
onkyokoi
Please Critique Low-Volt (Home Automation) Plan/Proposal
GW/Houzz Community, As always, I want to thank this...
Andrew K.
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™