Ground /Bonding

Could somebody tell me the difference between netural and earth ground. My garage has an earth ground bar and a netural bar, separate from each other. In the garage I am renting it has the netural and earth ground bars together. in the garage I am renting I installed an dusk to dawn light on a pole out side, on the light I have the standard netural, hot , and copper ground wires .. does the netural wire and copper wire from the light go to the bonded netural and earth ground in the garage. Is it true now that ever thing I hook up in the rented garage , The netural wire becomes the ground wire. BLACK HOT , WHITE GROUND.
Thanks
Ron

 

It depends on where the power is coming from.

At the main panel (The one directly connected to the meter and not being fed by any other panel) the neutral and ground are connected at a common bus.
At any other subpanel being fed from the main panel, the neutral and ground bars are separate. The only place they connect to each other is in the Main panel.

If the subpanel is in a separate building from the one which houses the main, then the ground bus is also connected directly to earth thru a grounding rod.

If your garage panel is really a subpanel, the ground and neutral must be separated. You would have a separate neutral bus, not connected to the panel, ground or anything but a white wire going to the main panel.
Your pole light should have 3 wires, a hot (red or black), a neutral (white or gray) and a ground (bare or green) . Each of these would connect to its own bus in the sub.

If your garage panel is in fact a main, then the neutral and ground would connect to the same bus.

 

I'm afraid gounding and grounded has confused people for a long time. New panels come with an extra screw, this screw called a bonding screw is to be installed at installation in the neutral buss, connecting the neutral buss to the box. If the bonding screw is not connected the panel is set up as a subpanel. If it is connected the panel is set up as a panel to be used as the first panel in the installation. Panels arrive from the manufacturers with two or more busses. Sometimes these busses are connected together and have to have a jumper or bar removed to separate the neutral and ground buss; sometimes they are already separated. A panel (the neutral and ground connected together) requires a ground electrode a subpanel does not have the neutral and ground made together At the panel the neutral and ground are connected together with the grounding electrode conductor. This is the terminating point of the ground system to the service and the neutral. Should the ground and neutral be connected together at any other point downstream in the system it would provide a path for current flow through bare conductors, equipment, buildings, people or any other conductor, therefore a grounding electrode would be required at that point.

So as you can see the neutral and ground wires are competly different although in some ways they work for the same purpose safety.

 

Any branch-circuit that supplies 120 volts to the connected loads has a Neutral conductor which is the "identified" conductor. This conductor is ALWAYS White and is an insulated wire that conducts current.At the service all Neutrals connect to the service,or utility Neutral which is the GROUNDED System Conductor which conducts current equal to the sum of the branch-circuit Neutral currents.At the service the system Neutral is connected to earth,or Ground,by a GROUNDING electrode conductor which is the SYSTEM Grounding Conductor.All interior circuits supplied from the service have an EQUIPTMENT Grounding Conductor which connects to the System Grounding Conductor at the service.For non-metallic cable this would be a bare conductor which is usualy referred to as "Ground",Ground being any point with a conductive path back to the Grounding connection at the service. The Neutrals of branch-circuits beyond the service are insulated from Ground.A White wire in a branch-circuit -the Neutral-is a Grounded conductor that conducts current. A bare wire is a Grounding conductor that will only conduct current when a "live" wire makes contact with Ground.