How do you get 208 voltage?

208 volts is the phase to phase voltage on a three phase low voltage system. In a split single phase service, the voltage is 120/240. In a three phase service, the voltage is 120/208. This is due to using a different transformer configuration. In the above, the first number is the phase to neutral reading, and the second is the phase to phase reading. For example, 120/240 and 120/208 both provide 120v on standard receptacles, but when using a dryer, or hot water heater, for example, that appliance would be using 240v or 208v, respectively.