Mule said:
Will the total current read, with, ONLY the two "out of phase" conductors passing through one CT cancel one another? I know if they are "in phase" that's how you multiply,or add, but never thought about this...:-?
You're getting it. That's why, when using CT's for metering, you have to get the phasing correct. CT's add currents in phase, which is why you can use one CT for parallel conductors.
If you were to run all service conductors through a single CT, you would read no current, unless there was an accidental contact between a hot wire and a grounded surface (other than the neutral).
So if this is true, and you had a ground fault, or current going somewhere elese, the current read on the ct on the two phases....WOULD be imbalanced, and thus trip?
Exactamundo! That's current that 'leaks' out of the loop on the load side of the GFCI. As long as the neutral passes through the CT also (whcih it does with GFCI's), its current is included it the sensing.
As long as the supply has a grounded conductor, accidental contact between a hot wire and earth or other grounded surface (other than another conductor passing through the CT) will be sensed.
Note that contact between circuit conductors, even including the neutral, are not protected against. With a non-grounded service, an accidental contact won't develop a current the GFCI can detect.
Also, you could even have a dozen conductors passing through a CT. As long as any current in any conductor is balanced by current in another one, the CT detects no net current.
