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Why is the fuse not used in the neutral ?

Fuses are primarily designed to protect electrical circuits from overcurrent conditions that could lead to damage or fire hazards. In most electrical installations, fuses are placed in the hot (live) conductor rather than the neutral conductor. Several reasons contribute to this practice:

  1. Safety Concerns:
    • Placing a fuse in the neutral conductor could create a safety risk. If a fuse were installed in the neutral and opened the circuit during a fault, the neutral conductor would become disconnected, potentially leaving the entire circuit and connected devices without a reference to ground. This condition, known as an open neutral, can lead to hazardous voltages appearing on supposedly “neutral” wires.
  2. Balanced Loading:
    • In a properly balanced electrical system, the currents flowing in the hot and neutral conductors should be equal under normal operating conditions. Placing the fuse in the hot conductor ensures that the protection is applied to the conductor carrying the load. If a fault occurs, the fuse in the hot conductor opens the circuit, disconnecting power and preventing further damage.
  3. Grounding System:
    • In many electrical systems, the neutral conductor is also the grounding conductor. Placing a fuse in the neutral could interfere with the grounding function, leading to potential safety issues and difficulties in maintaining a proper ground reference.
  4. Fault Detection:
    • Placing the fuse in the hot conductor allows for effective fault detection. If a fault occurs, such as a short circuit or excessive current draw, the fuse in the hot conductor quickly interrupts the circuit, preventing damage and providing a clear indication of the fault location.
  5. Code Compliance:
    • Electrical codes and standards, such as the National Electrical Code (NEC) in the United States, generally dictate the placement of fuses in the hot conductors for safety reasons. Adhering to these codes ensures that electrical installations meet recognized safety standards and regulations.
  6. Preventing Open Neutral Hazards:
    • Placing fuses in the hot conductor helps prevent open neutral hazards. In the event of a fault, the circuit is disconnected, and the potential for dangerous voltages on the neutral is minimized. This is crucial for the safety of both people and electrical equipment.
  7. Maintaining Circuit Continuity:
    • Placing the fuse in the hot conductor allows for better continuity in the event of a fault. If the fuse is blown, only the hot conductor is interrupted, while the neutral conductor remains connected, ensuring a more stable electrical system.
  8. Common Practice:
    • Industry standards and common practices have established the convention of placing fuses in the hot conductor. This consistency facilitates uniformity in electrical installations and maintenance procedures.

In summary, fuses are not placed in the neutral conductor for reasons related to safety, proper circuit operation, grounding considerations, fault detection, compliance with electrical codes, and industry practices. Placing fuses in the hot conductor ensures effective protection against overcurrent conditions while minimizing the risks associated with open neutral scenarios.

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