What is the required grounding method for metal electrical boxes?

The required grounding method for metal electrical boxes involves grounding through the conduit. This method is effective because it utilizes the metal conduit as a conductive path that connects the electrical box to the ground. When properly installed, the conduit ensures that any fault current is safely carried away, helping to prevent electric shock hazards. This is especially important in environments where safety must be prioritized.

Grounding through the conduit also complies with the National Electrical Code (NEC), which mandates that metal boxes must be properly grounded to provide a shield against electrical faults. By ensuring that the metal electrical box is grounded this way, it reduces the risk of a shock if a fault occurs within the wiring.

The other methods mentioned, such as no grounding required, direct grounding with a stake, or grounding with plastic insulators only, do not meet the safety standards necessary for metal boxes. Metal boxes, by their nature, need a reliable and effective grounding method, which is why grounding through the conduit is the correct choice.