Green main bonding jumper screws furnished with residential type panels should be installed in ___.

• A. Sub panels
• B. Main panels only
• C. Meter bases
• D. Main and sub panels

Answer: (B)

The main bonding jumper is used to bond the neutral path to the equipment grounding path at the service equipment. In the main service panel, the neutral bus must be bonded to the enclosure, so the green bonding screw (main bonding jumper) is installed there to complete that bond. In subpanels, neutrals must be isolated from the enclosure and from grounding, so no bonding jumper is installed. Meter bases aren’t where this bonding is applied in typical residential setups, and placing the bond in a subpanel would defeat the required isolation. So, the green main bonding jumper screws should be installed in the main panel only.