22
Installation
Wiring
Once you’ve planned the network and strung the cable, you can connect the WattNode meters.
●
The Modbus terminals (
A-
,
B+
,
C
, and
X
) are completely isolated (4500 Vac RMS isolation)
from dangerous voltages, so you can connect them with the meter powered. They are also
isolated from the meter’s earth ground and neutral connections.
●
When connecting WattNode meters to a PC or monitoring device, connect all “
A-
” terminals
together, all “
B+
” terminals together, and all “
C
” (common) terminals together. In most cases,
if you swap “
A-
” and “
B+
”, WattNode Modbus meters can auto-detect the polarity and com-
municate correctly.
Note:
if your RS-485 network isn’t properly biased (one terminal more
positive than the other), then the auto-detect feature will not work.
●
You may put two sets of wires in each screw terminal to make it easier to daisy-chain the
network from one device to the next. If you do this, we recommend that you twist the wires
tightly together before putting them into the screw terminal to ensure that one wire doesn’t
pull free, causing communication problems.
●
If you are using shielded cable, you may use the shield to provide the Modbus common “
C
”
connection between all devices on the network.
●
Connect the cable shield or Modbus common (if there is no shield) to earth ground at just the
Modbus master end of the cable. Grounding both ends can cause ground loops. Leaving the
common floating risks damaging the RS-485 circuitry.
Installation Summary
1) Mount the WattNode meter.
2) Turn off power before installing solid-core (non-opening) CTs or making voltage connections.
3) Mount the CTs around the line voltage conductors being measured. Take care to orient the
CTs facing the source of power.
4) Connect the twisted white and black wires from the CT to the six position black terminal
block on the meter, matching the wire colors to the white and black dots on the front label.
5) Connect the voltage wires including ground and neutral (if present) to the green terminal
block, and check that the current (CT) phases match the voltage measurement phases.
6) Set the Modbus network address and baud rate with the DIP switches.
7) Connect the pulse output terminals of the meter to the monitoring equipment.
8) Apply power to the meter.
9) Verify that the LEDs light correctly and do not indicate an error condition.
