In the case of a "gutter service" installation, is it permissible to install a main bonding jumper in the main-lug-only panelboard?

In a "gutter service" installation, the presence of a main-lug-only panelboard poses specific constraints regarding the installation of main bonding jumpers. A main-lug-only panelboard does not contain a main circuit breaker; therefore, it relies solely on the lugs for connecting incoming conductors. The National Electrical Code (NEC) specifies that bonding jumpers must be connected in specific ways to ensure the effective functioning of the grounding and bonding systems.

In installations where a main bonding jumper is required, it must be connected to a panel that includes a main disconnecting means, such as a main circuit breaker. This ensures that the electrical system can adequately manage fault currents and provide a clear path for them to safely dissipate to ground. The absence of a main circuit breaker in a main-lug-only panelboard complicates this bonding process, as it undermines the integrity and safety of the grounding system, which is crucial for preventing shock hazards and maintaining overall system reliability.

Thus, in the context of a "gutter service" installation, the absence of a main disconnecting means in a main-lug-only panelboard makes it impermissible to install a main bonding jumper, adhering to safety codes and practices established by the NEC.