Ensuring the proper color codes are used and understanding the difference between two-phase and three-phase current are the most important safety precautions for wiring 208-volt electrical systems. These systems use several hot wires, one neutral wire and a ground wire; all must be properly color-coded.
Electricians wire residential 208-volt electrical systems by combining two or three hot wires in a conventional electrical panel. Motors, kitchen ranges and clothes dryers typically require 208-volt single-phase current, which is fed by two hot wires through a two-pole circuit breaker. Heavier appliances typically require 208-volt three-phase current, which is fed by three hot wires in a three-pole circuit breaker.
While nationally recognized standards allow electricians to reliably identify which wires are hot, neutral or ground in a modern electrical system, many older buildings still feature electrical systems designed before local energy standardization took place. In general, any wire that is not green, white or grey is a hot wire and should be treated with caution. Commercial and industrial buildings, including apartment complexes, typically use three-phase 208-volt electrical systems that use different color codes. Any electrical panel featuring a color code that the operating electrician is not familiar with must be treated as an extra-high hazard area until all wires are safely de-energized and locked out.