It's a backup (also known as a secondary or earth ground) and is only there for safety in case the neutral fails. This way, the electricity doesn't end up energizing the body of the appliance. or a human body. Ensuring that this extension is done properly and safely, hence safeguarding your home and its inhabitants, depends on knowledge of sub-panel installations. It operates downstream from the main service panel, the primary connection point to the utility power grid. It has its own set of breakers and distributes power independently to a specific area — a garage, a workshop, a basement suite, an outbuilding, or any space that benefits from. According to the National Electric Code (NEC), there's no limit to the number of subpanels a house can have, provided usage doesn't exceed incoming capacity. If you understand a few key differences.
[PDF Version]