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What is the main bonding jumper and where do it find it in an electric panel?
Sunday, July 7, 2019
The main bonding jumper connects the service neutral wiring to the grounding electrode conductor(s) (GEC), and also to the service enclosure (panel box). By connecting these three components together, it eliminates any voltage potential (current) between them.
This is a big deal. “The main bonding jumper at the service panel is the most important electrical connection in the building,” according to Douglas Hansen, an electical expert and one of the authors of the CodeCheck book series. Because of this bonding connection, you can touch the metal panel box and not risk being shocked.
Modern panels have a green bonding screw at the head of the neutral terminal bar, which indicates bonding. So look for the green screw. The bonding may also be a short strap or wire to the panel box from an insulated terminal bar in some panels, like in the photo above. The grounded (neutral) terminal bar in a service panel is the heart of an electrical distribution system because it ties together with the equipment grounding conductors (ground wires), grounding electrode conductor (wire to ground rod or other type ground), and the service enclosure (panel box) via the bonding jumper.
Because any subpanels past the service panel must have the ground wires bonded, but not the neutral wires, panels that are designed to be used for either a service panel or subpanel often have a bonding jumper or connector bar between terminal bars that can be removed from the neutral bus for subpanel installations.
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