14
Overview
The voltage and CT wires may be wired
out of phase.
The best approach is to visually verify that everything is wired
correctly, but if that is not a feasible option, then follow
PROCEDURE B
below.
The WattNode is not functioning
correctly.
If another WattNode with the same model number is installed
and working, a suspect unit may be tested by disconnecting the
screw terminals from the working unit, and plugging them into
the suspect unit. If the suspect unit works correctly, then most
likely it is the wiring, and not the WattNode that is at fault.
PROCEDURE A:
1.
Either remove power from the WattNode or unplug the CT screw terminals before working with the
CT wires.
2.
Check each CT in turn. Disconnect all other CTs and jumper their screw terminals with a shorting
wire.
3.
Check that the power is not zero. If the power is zero, then reverse the CT wires (white to black and
black to white) and check again. If the power is still zero, then go to
PROCEDURE B
.
PROCEDURE B:
1.
Either remove power from the WattNode or unplug the CT screw terminals before working with the
CT wires.
2.
Check each CT in turn. Disconnect all other CTs and jumper their screw terminals with a shorting
wire.
3.
To order the phases correctly, match each CT to the pair of screw terminals that results in the largest
power. If the reported power on a pair of screw terminals is zero, then also try reversing the CT wires.
Throughout this test, unused CT inputs must be jumpered with a shorting wire between the white and
black dots. In addition, if the power level of the load being measured is changing significantly, then
this test may not yield correct results.
PROCEDURE C:
1.
Since some CTs may produce little or no output below 5% of rated current, verify that at least 5% of
the CT’s rated current is flowing through the CT. Use a clamp-on style current meter to measure the
current in the wire that passes through the CT. If a clamp-on current meter is not available, go on to
step 2.
2.
Measure AC voltage across the CT wires (probe the screw terminals). If the voltage is less than 3 mV,
then a) less then 5% of the CT’s rated current is flowing, or b) the CT is defective. If the voltage is
more than 333 mV, then a) more than the CT’s rated current is flowing, b) the CT is defective, or c)
the CT is not a 333 mV output CT. If you suspect that the CT may be defective, then a clamp on
current probe may be used to verify the current flowing in the wire. If the clamp-on probe indicates
that an AC current ranging from 5% to 100% of the CT’s rated current is flowing and yet the voltage
across the CT is not in the range of 3 to 333 mV, then the CT is probably bad. As a final test, unplug
the CT screw terminals from the WattNode and measure the voltage again. If it is significantly
different, then the WattNode may be defective.
