What must the neutral of a subpanel be?

The neutral of a subpanel must be floating when it is located in a separate building or structure from the main service panel. A floating neutral means that the neutral conductor is isolated and not bonded to the ground or to any other metal parts within the subpanel. This is crucial for safety and proper operation of the electrical system.

The reason for having a floating neutral in a subpanel is to prevent ground loops and ensure that the current on the neutral conductor flows correctly back to the main panel without creating parallel paths that could pose a shock hazard. By keeping the neutral isolated, it protects the system from potential electrical faults that could arise from improper bonding or grounding interactions within the subpanel.

In addition, when a subpanel is installed in a detached structure, the grounding system and the neutral must be carefully considered according to electrical codes. This typically means that while the equipment must be properly grounded, the neutral must not be bonded to the ground or any metal parts of the panel to maintain system integrity.

Understanding this principle is essential for ensuring compliance with the National Electrical Code (NEC) and enhancing electrical safety in various installations.