Portable generators that have the winding center-tap (neutral) bonded to the frame by the manufacturer are primarily intended for use where not connected to a building wiring system.

Generators that are designed to be permanently connected to a building wiring system through a transfer switch are usually manufactured with the neutral isolated from the frame (floating), as shown in Diagram 1.

Note - These diagrams do not represent actual installations, and are intended to illustrate basic principles only.

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Because the grounded (neutral) conductor is not switched in the transfer switch, no other grounding electrode connection is required at the generator.

If a generator that has the winding center-tap (neutral) bonded to the frame is used with a transfer switch, as in Diagram 2, the switch should break the grounded (neutral) conductor, which will require the generator neutral to be grounded to an acceptable grounding electrode.

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Ed

[This message has been edited by electric-ed (edited 11-21-2002).]