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What should I do with unused voltage and CT input phases on the WattNode? Should I jumper them?

Our recommendations have changed over the years and may vary somewhat depending on your configuration. There are really two issues:

Floating Mains Voltage Inputs

If any of the mains voltage inputs (the 5 circuit green screw terminal block) are left floating, the WattNode meter might think that an unused voltage phase is active, when it actually is not. This normally is only a problem if the meter is not grounded.

If the diagnostic LEDs or the WattNode readings indicate non-zero values on a phase that is disconnected:

  • First make sure the meter is grounded. On wye models, connect a jumper wire from the the ground terminal to the neutral N terminal.
  • If that doesn’t solve the problem or isn’t feasible, then jumper the unused mains input to the meter’s neutral or ground terminals.

Floating CT Inputs

So long as the mains voltage for an input phase measures near zero volts, the WattNode meter considers that phase “inactive” and won’t measure any power or current on that phase. Because of this, it is rarely necessary to jumper (short) unused CT inputs. However, there are cases where you want to connect a mains voltage to the WattNode meter without a matching CT. In rare cases, its also possible that the meter might incorrectly sense a voltage phase as being active when it isn’t being used. In either of these cases,

  • Jumper the unused CT input with a short length of wire between the white and black circles on the label.