California Electrical Contractor (C-10) License Practice Exam

Backfeeding a panel means feeding power into a panel from a source other than the normal utility service (such as a generator or inverter) and doing so only with a proper interlock or interconnection that isolates the panel from the utility when the alternate source is energized. This setup is used to provide temporary or emergency power during an outage, using a transfer switch or a listed interlock to prevent any backflow of power onto the utility lines. The interlock ensures the main service disconnect and the alternate source cannot be energized at the same time, protecting lineworkers and equipment. Without interconnections, backfeeding can be dangerous and is not allowed, and simply attempting to feed a panel from another source without proper interconnection could energize the grid or the wrong parts of the panel.