This standard describes installation procedures for the following: (a) Generator sets permanently installed at one-family dwellings to provide backup power. These are usually rated 120/240 volts, single-phase, three-wire. However, some large homes have three-phase electrical systems and use backup generators rated 120/208 volts, three-phase, four-wire. (b) Generator sets fueled by gasoline, natural gas, or liquefied petroleum (LP) gas.
ANSI/NECA 406-2003 history
2003ANSI/NECA 406-2003 Recommended Practice for Installing Residential Generator Sets