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9
4.3 Connecting a Current Transformer to the PBVI Board
If subfeed breakers are ordered with the unit, the phase CTs are installed and wired to the PBVI. The
neutral and ground CTs are also factory-supplied and wired to the PBVI board.
Since the CTs must be installed on the subfeed breaker’s neutral and ground cables, they cannot be
installed in the factory. They are located in the bottom of the unit in front of the transformer.
CTs have an arrow, white dot or similar marking that depicts how to position the CT on the cable to
ensure accurate readings. The arrow, white dot or similar marking must face the load when installing
the CT on the ground and neutral cable. Route the neutral and ground cable through the core of the
CTs and wire-tie the CT to the cable.
If subfeed breakers are installed in the field, up to five CTs may be installed to monitor a subfeed
breaker (three phases, neutral and ground). The neutral and ground CTs may be omitted if monitor-
ing of neutral and ground is not required.
On large branch circuit breakers, ground and neutral is not monitored.
There are two 18-pin terminal blocks on the PBVI for large branch circuit breakers and/or subfeeds—
one for Panelboard A and one for Panelboard B.
The circuit board is marked with a triangle to indicate Pin 1.
• Pin 1 should be used for the white wire of CT1 (Phase A)
• The black wire should be connected to Pin 2.
• The same pattern will follow for the remaining CTs.
After all CTs are installed, use the Configuration tool to label and set alarm parameters. To configure
the Liebert LDM, see 5.5.11 - Add or Delete a Circuit Breaker.
If the Power Distribution Center is supplied with optional isolated ground, the isolated ground circuit
can be monitored by the Liebert LDM.
• Connect the isolated ground CT to Pins 17 and 18 on the two 18-pin terminal blocks on the PBVI.
• Connect the isolated ground CT white wire to Pin 17 and the CT black wire to Pin 18.
Refer to the following example and Table 2 for wiring configuration details.
Example: When installing a subfeed breaker where the three phases, neutral and ground will be
monitored, the CTs should be wired as follows:
If neutral and ground will not be monitored, Pins 7-10 may be used instead for a second subfeed
(Phase A and Phase B CTs).
Pin Wiring
1 Phase A CT White wire
2 Phase A CT Black wire
3 Phase B CT White wire
4 Phase B CT Black wire
5 Phase C CT White wire
6 Phase C CT Black wire
7 Neutral CT White wire
8 Neutral CT Black wire
9 Ground CT White wire
10 Ground CT Black wire
▼
CT for neutral
and ground
Five CT
connection
CTs for the
three phases