Why must metal parts of premises wiring be bonded?

Bonding metal parts of premises wiring is essential primarily to ensure an effective path for fault current. When a ground fault occurs—meaning that there’s an unintended path for current to flow outside of the normal circuit—it is crucial that the fault current can find its way back to the ground quickly. This is important because it helps to trip circuit protection devices, like breakers or fuses, reducing the risk of shock or fire hazards.

By bonding metal components together, you reduce the resistance that the fault current encounters, ensuring that it reaches ground efficiently. This quick response is vital for the safety of the electrical system and those using it.

In contrast, while preventing electrical noise, facilitating maintenance, and enhancing conductivity are important considerations in electrical systems, they are not the primary reasons for bonding metal parts in the context of electrical safety and fault management. Therefore, the focus on quickly clearing a ground fault reflects the critical safety function of bonding.