Wiring Diagrams for Schneider Electric Masterpact NT and NW Circuit Breakers

Quick Guide from the Manual

This document provides essential wiring diagrams and terminal markings for the Masterpact NT and NW Universal Power Circuit Breakers. Users must pay close attention to the following critical installation requirements:

• Jumper Settings: Do not remove factory-installed jumpers between Z3, Z4, and Z5 unless ZSI (Zone Selective Interlocking) is connected. Do not remove the factory-installed jumper between T1 and T2 unless a neutral CT is connected. Do not install a jumper between T3 and T4.
• Power Supply Isolation: The 24 Vdc power supply for the trip unit must be separate and isolated from the 24 Vdc power supply used for communication modules.
• Induced Voltage Prevention: To prevent shunt trip or shunt close failure due to induced voltages at terminals C2 and A2, keep wiring as short as possible (under 10 feet / 3 meters). If this is impossible, use an interposing relay near terminal C2 or A2.
• Spring Charging: When using remote operation features, ensure a minimum of four seconds for the spring charging motor (MCH) to completely charge the closing springs before actuating the shunt close (XF) device.

Wiring Diagrams

The manual provides detailed schematic diagrams for the Power, Trip Unit, and Remote Operation sections of the circuit breakers. These diagrams illustrate the connections for various components, including:

• Trip Unit: Connections for communication (E1-E6), logical selectivity (Z1-Z5), external power supply (F1-, F2+), and external phase voltage sensing.
• Remote Operation: Connections for shunt trips (MX1, MX2), shunt close (XF), ready-to-close contact (PF), and the spring-charging motor (MCH).
• Auxiliary Contacts: Wiring for OF (Open/Closed) contacts and EF (Combined Connected and Closed) contacts.

Terminal Markings

The document includes comprehensive tables for identifying terminal markings for both Push-In and Ring type terminals. These tables cover:

• Cell Switches: CD, CE, and CT switch positions (Disconnected, Connected, Test).
• Trip Unit Terminals: Mapping for COM, UC1, UC2, UC3, M2C/M6C, SDE, and other control inputs.
• Remote Operation Terminals: Mapping for MN/MX, XF, PF, and MCH devices.

Note: Fixed-mounted circuit breakers do not have cell switches (CE, CD, CT).

Communication and Additional Connections

The manual details the connection of the Communications Option, including the Cradle Communication Module (CCM) and Circuit Breaker Communications Module (BCM). It provides a recommended wiring schematic for communicating style shunt trip or shunt close coils, emphasizing the importance of the bypass circuit through terminal C2/A2, which is for momentary duty (0.5 sec) only.