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What is the green screw in QO and HOM load centers?

Issue:
Many load centers includes in the carton a green screw inserted through a small white card. What is the purpose of the green screw? When should it be used?

Product Line:
QO and HOM Load Centers

Environment:
Applies to Load Centers sold and installed in the USA.

Cause:
Some load centers include the green screw, but others do not. Is there a reason for that?

Resolution:
When a load centers is used as Service Equipment, the NEC requires that the neutral shall be bonded to the metal box. The Service Equipment is identified by the fact it includes the first disconnect of the incoming power from the Utility. For a single family house, many times the load center is the main panel, with the main breaker acting as the Service disconnect. In this panel, the green screw is used to bond (fasten) the neutral to the metal box. This is only done in the main panel. Any panels installed downstream of the main panel are called sub-panels, and the neutral in these panels must not bonded to the box. Since many Load Centers can be used as either the main panel, or as a sub-panel, we include the green screw with the load center to be used in the appropriate installation.
NOTE: The green screw is also commonly called the "Neutral Bonding Screw", or the "Bonding Screw".
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