NECA 406-2014

This standard describes installation and maintenance procedures for residential generators fueld by gasoline, natural gas, or liquefied petroleum gas (LP or propane) and permanently installed at one-family dwellings to provide backup power. Residential generators are usually rated 240/120 volts, single-phase, three-wire. Some larger one-family dwellings have three-phase electrical systems and may use backup generators rated 208Y/120 volts, three-phase, four-wire.

This standard also covers the installation of related items such as non-automatic (manual) or automatic transfer switches (MTS or ATS), disconnect switches, control panels, and fuel supply systems, and describes some electrical power distribution system design consideration related to the use of generators to supply important, non-emergency loads in single-family dwellings.

Residential generators are considered to be “optional standby power systems” in accordance with the NEC.