A green-colored screw should thread into the heavy gauge steel of this 200A service panel enclosure, securing the bonding jumper. At the center of the highlighted area in the photo, one can see that the screw was either removed or never installed.
This threaded ground bonding location ensures that the metal panel enclosure remains at zero voltage to the building and service grounding systems, and helps ensure that a low-impedance path for fault current on the panel enclosure will trip a breaker before serious damage occurs. A poor connection here could result in a high-impedance path for fault current. An ungrounded (‘hot’) conductor could contact the panel enclosure and discharge to ground through this poor connection at relatively low levels of current not sufficient to trip the breaker protecting the circuit. At least two hazards would result:
- The connection missing the screw could heat up and melt adjacent wire insulation, causing more trouble, or ignite the wooden surface on which the panel is mounted.
- The panel enclosure would remain energized until the fault is cleared, and could electrocute someone.
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- West Philly Tool Library Official site of WPTL, Philly’s own community tool lending library: like a book library, but tools!
- WestPhillyLocal .com Site name say sit all.
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