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