Product Families & Standards
What’s the difference between MCB, MCCB, and ACB?
MCB (e.g., S200): Final circuits, lower currents, fixed trip curves (B/C/D). MCCB (e.g., Tmax XT/Tmax T): Higher currents & fault levels, configurable/adjustable trips. ACB (e.g., Emax 2): Main incomers/bus ties, withdrawable options, advanced electronic protection.
RCCB vs RCBO—when should I use each?
RCCB: Residual-current (earth-leakage) protection only—pair with an MCB for over-current. RCBO: Combines MCB + RCD in one device—saves space and simplifies coordination.
IEC vs UL—how do I choose the right standard?
Match the device to your market/code: IEC: IEC/EN 60898-1 (MCB), IEC/EN 60947-2 (MCCB/ACB). UL/CSA: UL489 (branch protection), UL1077 (supplementary), UL1066 (ACB). Voltage systems, interrupting ratings, and labeling differ—select accordingly.
Selection & Coordination
How do I choose B, C, or D trip curves for an MCB?
B: Resistive/low-inrush loads. C: Mixed loads/small motors. D: High-inrush loads (transformers/large motors). Always check selectivity with upstream devices.
What interrupting rating do I need?
Determine the available fault current (AFC) at the installation point and choose a breaker whose Icn/Icu (IEC) or Interrupt Rating (UL) exceeds that value. If fault levels are high, use higher-capacity lines (e.g., S200M/S200P) or upstream current-limiting devices.
Installation, Accessories & Lifecycle
How do I achieve selectivity or back-up protection?
Use ABB’s selectivity/cascading tables to pair downstream MCB/MCCB with upstream devices (breakers or fuses). Provide: downstream current/curve, upstream type/rating, system voltage, and AFC.
Which accessories are commonly used and why?
Aux/Signal contacts (OF/SD): Remote status/trip indication. Shunt trip / Undervoltage release (UVR): Remote or emergency opening/interlocking. Rotary handles / Motor operators: Safe isolation or remote operation. Busbars / Feed-in blocks: Faster, cleaner panel wiring.
Can I replace legacy SACE Tmax T with Tmax XT or upgrade ACBs to Emax 2?
Often yes, but verify dimensions, terminals, accessories, protection settings, and standards. Re-commission with insulation checks, torque verification, and functional trip tests; update coordination studies as needed.