According to NEC Article 250, both the neutral and ground wires must be connected only in the main panel or at the first service disconnect. They should never be connected together downstream of the service equipment, such as in subpanels or other parts of the circuits. Whether you're a seasoned pro or just starting out, this comprehensive guide will give you practical. Grounding is a mechanism to protect distribution equipment and people under normal operating conditions, abnormal operational (overcurrent and overvoltage) responses, and hazardous conditions such as shocks. Grounding is necessary to assure correct operation of electrical devices, to assure safety. A distribution box is the heart of any electrical system. A grounding bar, also called a ground bar, earth bar, or PE bar, connects protective earth conductors and normally carries current only during fault conditions.
[PDF Version]