What type of service requires a grounded conductor?

The requirement for a grounded conductor is essential for all 120/240 volt single-phase services, as outlined in the National Electrical Code. Grounding and bonding are critical safety measures that help prevent electrical shock hazards and ensure proper operation of the electrical system.

In residential and many light commercial applications where 120/240 volt single-phase services are typically used, the grounded conductor plays a vital role in providing a return path for fault currents. This enhances the safety of the system by reducing the risk of electric shock and equipment damage. Moreover, it helps to stabilize the voltage levels and maintain the integrity of the electrical system by providing a reference point to ground.

Other types of service, such as three-phase services or higher voltage systems like 277/480 volts, also have grounding requirements but are governed by different conditions and contexts that may not universally apply to all installations. While commercial services greater than 200 amps do have specific grounding requirements, the blanket requirement for a grounded conductor specifically holds true across all 120/240 volt single-phase services, making this answer the most comprehensive and applicable across a wider range of electrical systems.