If you have 2 legs that measure 120 volts to ground and one that measure 208 volts to ground the voltage between the legs will be 240 volts not 208 volts. This is a delta system.

If there is 208 volts between each of the legs then all 3 will measure 120 volts to ground. This is a wye system.

The 208 volt leg on the delta system is only used for 3 phase loads.

Curt

Curt Swartz