Sub Meter

[mstrlucky74]

Can someone help me out and tell me what would be involved to install a new meter to meter each existing load shown. I believe you don't have to disconnect existing wires and you can get a "split" ct to go around the feeders? Thanks.

1. Is there a CT for each phase wire or one CT goes around all phase wires?
2. The CT's have wires/leads attached to them which then run to the meter?

 

[GoldDigger]

You need to have at a minimum one CT less than the number of circuit conductors.

If you wrapped one CT around all ungrounded conductors you would meter zero power for a balanced load.
If you know N-1 currents Kirchoff's law of currents let's you calculate the third.

BTW, you could theoretically use either split core CTs or Rogowsky coils (rope type). The meter needed may be different depending on that choice.


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[mstrlucky74]

You need to have at a minimum one CT less than the number of circuit conductors.


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?? Can you explain a little more why. Thanks.

 

[GoldDigger]

?? Can you explain a little more why. Thanks.

See edit of original post.
For example, for 120/240 single phase three wire a standard in-line meter will sense current in L1 and L2 only and in a small "cheat" will also not even have a voltage connection to the neutral. It makes the assumption that L1-N and L2-N voltages are equal.

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