Which type of bonding is never allowed in a subpanel according to electrical code?

In electrical installations, particularly in subpanel configurations, the bonding of ground and neutral is prohibited because it can create safety hazards and interfere with the proper operation of the electrical system. The main purpose of bonding the ground and neutral at the service entrance (the main panel) is to ensure system safety and facilitate fault current clearance. However, once the installation goes beyond this point to a subpanel, neutral and ground must remain separate to prevent parallel paths for neutral current.

If ground and neutral were to be bonded in a subpanel, it could lead to the neutral current returning on the grounding conductors. This situation poses several risks, such as the potential for electric shock if there is a fault, and interference with the grounding system’s ability to safely dissipate electrical faults. Keeping these systems separate at the subpanel ensures that grounding conductors are only used for fault protection and not for carrying return current, which is essential for maintaining safety and system integrity.

Therefore, the prohibition of bonding ground and neutral in a subpanel aligns with established electrical codes to enhance safety and functionality within electrical installations.