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| You generally need a ground at the main panel and it doesn't hurt at the subpanels. You only bond ground and neutral at the main panel, never at the sub panels so you must feed subpanels with 4 wires carrying neutral and ground separately. That's what the National Electrical Code says and that's usually what states adopt. You don't want multiple bonds because then some of the unbalanced load current in the neutral would flow in the ground wires connecting the subpanels to the main panel and the grounds are not supposed to carry any load current, only leakage or short currents. A ground carrying neutral can put line voltage on a box or a appliance case leading to shock if the ground was to go open. That can be deadly. Ground is to protect the users from shock not to carry current.
You can't have too many ground rods unless you trip over them. For multiple rods space them a rod length apart minimum.
Gerald J, electrical engineer. | |
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ND electrical code ??? (ground rods)
