Liebert LDM user manual Connecting a Current Transformer to the PBVI Board

Installation

4.3Connecting 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.

CTs for the	CT for neutral	Five CT
three phases	and ground	connection

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:

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

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).

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