Quote:
Originally Posted by N2IXK
208V is also the phase-phase voltage of a 208Y/120V 3 phase system. This system allows 3 phase 208V power for running large motor loads like pumps and A/C units, as well as standard 120V power for ordinary receptacles and lighting WITHOUT the need for a step-down transformer. VERY common feeding apartment buildings and smaller commercial/industrial facilities during the 50s-70s. This is a fully balanced 3 phase wye setup, with no "wild leg". 208V between phases, 120V between any phase and the grounded neutral.
The only place where these systems can cause issues is with large single phase loads like baseboard heaters. They generally want 240V, and give significantly reduced output on 208V.
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The 208Y120V 3 phase system is still the most commonly used system in smaller commercial and apartment complexes that have elevators.
The NEC requires that no voltage over 120 volts to ground exists. The reasoning being, that a lot of repairs being done are performed by personnel not versed in higher voltage work. Also circuit breaker panels are lot less expensive.