||10-05-2012 07:52 PM
Originally Posted by astovall7
how can you tell what is 208 voltage 120 voltage is a black hot wire and a white neutral wire and 240 voltage is two hot wire black and red or black and white as hot what is 208 voltage:yes:
Sometimes you cannot tell just by looking at it. You tell for sure by measuring it using a voltmeter.
A 120/208 system may look the same as a 120/240 volt system, wire colors and all. The 120/208 volt system is not common in homes but may be found in apartment complexes with mixed commercial use such as stores and restaurants ont he first floor and dwelling units upstairs.
In a 120/208 volt system you find only 208 volts where you would expect to find 240 volts (hot to hot such as black to red), and the 120 volts is found in its normal places (hot to neutral)
Now you may wonder how you can have exactly three wires, red, white, and black, in your power feed cable and you get 120 volts from red to white, 120 volts from black to white, and 208 volts from red to black. Shouldn't the last one be the sum of the first two? The answer requires understanding of what is means to be out of phase but not diametrically (180 degrees) out of phase. That mathematical discussion is too complex for me to include here. Superficially a 120/208 volt service has two of the phases of a 208 volt 3 phase system with a symmetric neutral aka a 208 volt Y (wye or star) 3 phase system.