Originally Posted by TomM141
Ran a circuit to a home that we moved in to for workshop power tools. The main breaker panel had been replaced in the home to satisfy a home inspection issue so we now have a new cutler hammer breaker box. what I noticed is that when I removed the cover to put in the new 20 Amp Breaker for my power tool circuit the electrical who did the new wiring (replacing a fuse box) mixed and matched the Neutral wires (white coating) with the Earth ground (Bare) wires and placed some of each on what appears to have been the neutral bar and some on the Earth Ground Bar.. Th bars are mounted on the left and the right of the actual breaker bar. However there also appears to be a connector going from one bar (what I would call the neutral bar) over to the Earth ground bar. The Bar on the right is also connected to the braided wire coming in form the outside service while the Earth Ground Bar has a wire actually going to the Earth. It it acceptable and code to combine these wires (earth and neutral on the same bar(s)
Your panel sounds like it is set up for the service equipment
panel of the home. This panel, often referred to as the 'main' panel', contains the main breaker that will disconnect all power to the home.
Your cutler hammer panel has what is termed a 'split neutral' configuration in which a neutral bar is installed on each side of the panel. The connector you are referring to is a bonding bar between these two neutral bars essentially making them electrically joined. You will also notice there is a green screw installed either in the connecting bonding bar or one of the neutral bars that bonds the panel metal to neutral. This required in the service equipment panel because the utility neutral also is terminated to this neutral bar configuration. As you probably know the equipment grounding conductors of the branch circuits protected by the circuit breakers are terminated on these two bars along with the neutrals .... and so are the earth grounding electrode conductors. It is important to understand the difference.
The conductors going to electodes in the earth like ground rods and water pipes serve as the grounding electrode system which protects your property from lightning and other high voltage events. They also help stabilize voltages in the event of an open utility neutral. The bare wires and green wires connected to the two neutral bars from the branch circuits are your equipment grounding conductors. These are for human safety and carry fault current in the event of a phase fault to ground and are part of the effective ground fault path necessary for opening a circuit breaker and thereby preventing anything from becoming energized at line voltage that humans might touch. To these equipment grounding wires are protection against electrocution.
The key here is that your main panel is fed by 3 wires ...two hots and a utility neutral. The utility neutral is the common link to the transformer center tap and essentially completes all 120 volt branch circuits and ground fault events with the transformer. It is because of this that both neutral and ground are bonded to each other and the utility neutral at the service equipment panel. Both must use the utility neutral to function properly.
The neutral of course is the current carrying wire for 120 volt circuits while the equipment ground will only carry current in the event of a ground fault and then breifly because a circuit breaker will open the branch circuit that has the fault and denergizing that branch ciruit to protect human safety.
Heres a few diagrams that show you why neutral and ground are bonded at the service equipment. Notice the common link to the transformer is via the utility neutral. Also understand that electricity at voltage levels for residences of 120/240 volt 3 wire single phase will not have current following to earth over the grounding electrode conductors due to their connection (bond) to the neutral bar in the service equipment. The resistance on the path to ground is too high when compared to the low impedance/resistance over the utility neutral to the transformer.