9
Install the CTs around the conductor to be measured and connect the CT leads to the meter.
Al-
ways turn off power before disconnecting any live conductors.
Split-core CTs can be opened for installation around a conductor. A nylon cable tie may be se-
cured around the CT to prevent inadvertent opening. If using solid-core CTs, put the line conduc-
tors through the CTs as shown in
above.
CTs are directional. If they are mounted backwards or with their white and black wires swapped the
measured power will be negative. The status LEDs indicate negative measured power by flashing
red.
When installing WattNode Revenue models, be sure to only use IEEE C57.13 class 0.6 current
transformers, such as the Accu-CT; other CTs are less accurate and may not provide revenue ac-
curacy. Contact sales for more information on appropriate CTs.
3.4.1 CT Wiring
The current transformers connect to the six position black screw terminal block. Connect the
white and black CT wires to the meter terminals marked
Ø
A CT
,
Ø
B CT
, and
Ø
C CT
(see
Figure 1
above). Excess length may be trimmed from the wires if desired. Connect each CT with the white
wire aligned with the white dot on the label, and the black wire aligned with the black dot. Note
the order in which the phases are connected, as the line voltage phases
must
match the current
phases for accurate power measurement.
3.5 Connect the Output Signals
●
The meter outputs are electrically isolated from dangerous voltages.
●
If the output wiring is near line voltage wiring, use wires or cables with a 300 V or 600 V rating
(not less than the service voltage).
●
If the output wiring is near bare conductors, it should be double insulated or jacketed.
●
You may install two wires into each screw terminal by twisting the wires together, inserting
them into terminal, and securely tightening. Note: a loose wire can disable an entire network
section.
●
Use shielded twisted-pair cable to prevent interference. If there is no common conductor, con-
nect the shield to the
C
terminal.
3.5.1 Modbus RTU
The WattNode Modbus meter can be connected to PCs with RS-485 interfaces, gateways, data
loggers, and other devices that accept RS-485 Modbus RTU.
Use DIP switches 1-7 to select the Modbus address (1 to 127).
DIP Switch
1
2
3
4
5
6
7
Up
(1) Value
1
2
4
8
16
32
64
Address
Examples
1
1, Up
0, Down 0, Down 0, Down 0, Down 0, Down 0, Down
1+2+4 = 7
1, Up
1, Up
1, Up
0, Down 0, Down 0, Down 0, Down
4+16 = 20
0, Down 0, Down
1, Up
0, Down
1, Up
0, Down 0, Down
1+2+16+32
+64 = 115
1, Up
1, Up
0, Down 0, Down
1, Up
1, Up
1, Up