14
Hardware
Installation
Place the CTs around the line wires as shown in section
2.2 Measurement Configurations
. Split-core
(opening) CTs may be placed around the line wires without disconnecting the wire. After a split-core CT
has been placed around a wire, a nylon cable-tie should be secured around the CT to prevent inadvertent
opening. Toroidal CTs require that the wire be disconnected before passing it through the opening in the
CT. Always remove power before disconnecting any live wires.
Next, connect the CTs to the WattNode. The CT inputs to the WattNode are sensitive to ESD (electrostatic
discharge), so you should discharge yourself by briefly touching the service panel case or some other
grounded metal object before connecting the CTs to the WattNode. Route the twisted black and white
wires from the CT to the WattNode. Any excess length may be trimmed from the wires if desired. Strip or
trim the wires to expose 1/4" (6 mm) of bare wire. Do not leave more than 5/16" (8 mm) or less than 7/32"
(5 mm) of bare wire. The current transformers connect to the black screw terminal block. 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, because the voltage phases must match the current
phases for accurate power measurement. Any unused CT inputs must be shorted. You may trim short
sections off the end of the CT wires to use as jumpers. Be careful to leave insulation on the exposed
portion of the jumper(s) to prevent shock or shorting danger.
The final installation step for the CTs is part of the network installation. The full-scale current rating of the
CTs must be programmed into the WattNode so that it can correctly scale the output readings. For detailed
instructions see section
4.2.3 Energy Configuration
. To facilitate this step, the installer should record the
CT full-scale current as part of the installation record for each WattNode. If the wires being measured are
passed through the CT(s) more than once, then the recorded full-scale CT current is divided by
n
where
n
is
the number of times that the wire passes through the CT.
2.5 Connecting Voltage Terminals
Disconnect power—by shutting off circuit breaker(s) or removing fuse(s)—before connecting the voltage
lines to the WattNode. The WattNode must be connected to voltage lines which are protected by fuses or
circuit breakers. Connect each voltage phase input to a circuit breaker on the required phase. If there is
more than one circuit breaker on a phase, then any one of the circuit breakers may be used. When installing
multiple WattNodes at the same site, it may be easier to provide separate circuit breaker(s) for the
WattNodes.
The detachable screw terminals may be installed or removed while power is applied. CCS recommends the
use of insulated gloves whenever working with a live circuit.
When connecting the WattNode, do not place more than one voltage wire in a screw terminal; use separate
wire nuts or terminal blocks if needed. The screw terminals handle wire up to 12 AWG. Prepare the
voltage wires by stripping the wires to expose 1/4" (6 mm) of bare wire. Do not leave more than 5/16" (8
mm) or less than 7/32" (5 mm) of bare wire. Connect each voltage line to the white terminal block as
described in section
2.2 Measurement Configurations
. Double check that the voltage line phases match
the phases to which the CTs are connected. After the voltage lines have been connected, make sure both
terminal blocks are securely installed on the WattNode.
The WattNode is powered from the voltage inputs: phase A to neutral, or phase A to phase B for delta
models. If the WattNode is not receiving at least 80% of the nominal line voltage, it will stop measuring
power. Since the WattNode consumes some power itself, a decision must be made about whether to place
the CTs before or after the connection for the WattNode, so as to include or exclude the WattNode’s own
power consumption (1.5 – 3.0 watts).
2.6 Network Wiring
CCS recommends that an experienced LonWorks network installer be consulted for network design,
including choice of transceivers, wiring, and termination. The WattNode may communicate over a twisted
pair network or over the power lines. Power line transceivers do not require additional network wiring, but
twisted pair transceivers require connection to a twisted pair network.
