AC 4 Pole MCB 20A, 32A, 40A, 63A

CNC 4 Pole MCB — Three-Phase Plus Neutral Miniature Circuit Breaker

The CNC YCB7-63N 4 pole MCB is a three-phase plus neutral (3P+N) miniature circuit breaker. It disconnects all four conductors — L1, L2, L3, and N — together in a single trip mechanism, giving complete isolation of a three-phase circuit. This is the standard choice for three-phase main incoming breakers in commercial, industrial, and large residential installations across Pakistan.

Unlike the 3 Pole MCB which only switches the three phases, the 4 Pole version also switches the neutral — essential for true isolation during maintenance, for three-phase solar inverter AC output, and for star-connected loads where the neutral carries unbalanced current. A fault on any phase trips all four poles simultaneously, preventing the dangerous single-phasing condition that destroys three-phase motors and compressors.

Rated at 400V AC with C-curve trip response and 6kA breaking capacity per IEC 60898-1, the YCB7-63N 4P handles three-phase DB feeders, motor circuits with neutral, 3-phase pump starters, and solar inverter AC output protection. CNC Electric is a trusted MCB brand in Pakistan with a 5-year replacement warranty on all circuit breakers.

Specifications

Why 4 Pole (3P+N) Over 3 Pole?

The key difference between a 3 Pole and a 4 Pole MCB is whether the neutral is switched together with the phases. For Pakistani installations, the 4 Pole version is preferred in these situations:

Three-phase main incoming breaker. When WAPDA supply arrives on four conductors (3 phases + neutral), the main breaker should disconnect all four during maintenance or fault. A 3 Pole leaves the neutral connected; a 4 Pole fully de-energises the DB. Safety personnel can service the downstream panel only after full isolation — that requires a 4 Pole.

Three-phase solar inverter AC output. Hybrid and on-grid 3-phase solar inverters generate their own live-and-neutral AC output. When the inverter is off, the neutral from the inverter side must be isolated from the neutral from WAPDA to prevent parallel-path issues. A 4 Pole MCB on the inverter output ensures the inverter neutral is switched together with the three phases.

Star-connected three-phase loads. Loads wired in star configuration (heating elements, some motors, unbalanced lighting systems) use the neutral as a return path. The neutral can carry significant current under unbalanced conditions, so it must be switched with the phases during fault or maintenance.

Generator and ATS panels. When WAPDA and generator supplies are alternated via an Automatic Transfer Switch or manual changeover, the neutral from each source is typically separate. The 4 Pole MCB on each source ensures the neutral of one source never conflicts with the neutral of the other.

Use a 3 Pole instead if the load has no neutral (delta-connected motors, pumps, compressors), or if the neutral is handled separately via a common busbar.

4P MCB — Amperage Selection Guide

Above 63A: move to a 4-Pole MCCB rated 100A–1600A for larger commercial and industrial installations.

Three-Phase Motor Sizing with 4 Pole MCB

For motor feeders, select the 4 Pole MCB at approximately 1.25× the motor full-load current on 400V 3-phase:

For motors with heavy starting inrush (star-delta starter, DOL on 15 HP+), consider a D-curve MCB variant or pair this C-curve with a dedicated motor-protection relay. For 3-phase solar inverter AC output, size the MCB at approximately 1.25× the inverter rated AC output current.

Typical Applications

3-phase main incoming breaker. Commercial shops, offices, small factories, large homes with 3-phase WAPDA supply. The 63A 4P sits at the top of the DB — all power flows through it first. Install a phase sequence relay immediately after for phase-reversal protection.

3-phase solar inverter AC output. On-grid and hybrid 3-phase solar inverters up to 22 kW. The 4P on the inverter output ensures the inverter (its live and neutral) can be completely isolated from the house DB during maintenance. For 25 kW+, use a 4P MCCB.

3-phase motor feeder with neutral. Star-connected 3-phase motors and loads (unbalanced lighting, heating elements, some HVAC systems) where the neutral carries actual current.

Generator 4-wire changeover panel. When the generator and WAPDA each provide their own neutral, the 4P MCB on each source ensures proper isolation during ATS or manual switching.

Agricultural tube-well panels. Submersible pumps with 3-phase star-connected motors, especially when the panel is remote and requires full isolation for safe servicing.

Commercial kitchen panels. 3-phase sub-DBs feeding ovens, heaters, chillers — often unbalanced loads with significant neutral current.

Installation Notes

Wire the neutral through the 4th pole. Connect L1 to pole 1, L2 to pole 2, L3 to pole 3, and neutral to pole 4. All four poles trip together on a fault anywhere in the circuit.

Use 6mm² copper for 32A and below; 10mm² for 40A; 16mm² for 63A. Size the neutral conductor the same as the phase conductors (not reduced) for unbalanced loads.

Torque terminal screws to 2.5 Nm. Re-check tightness after 3 months of service. At 63A continuous, a loose terminal overheats and is a major cause of panel failures in Pakistan.

Plan DB space: this 4 Pole MCB is 72mm wide (4 modules). An 18-way DB with one 4P main incomer uses 4 modules, leaving 14 for branch circuits.

Related Products

• Three-phase without neutral → 3 Pole MCB 16A-63A (Rs.1,350)
• Single-phase branch circuits → 1 Pole MCB 2A-63A (Rs.425)
• Single-phase main incomer → 2 Pole MCB 10A-63A (Rs.850)
• Above 63A or industrial fault levels → MCCB 4P 100A-1600A
• 3-phase generator auto-switching → ATS 4-pole
• 3-phase manual changeover → Changeover switches 4P
• Phase-sequence / reversal protection → Phase Sequence Relay
• 3-phase voltage protection → VA Voltage Protector
• Motor contactor for start/stop → Magnetic contactors
• 3-phase SPD / surge protection → SPD 4-pole
• Complete 3-phase DB → DB boxes + breakers
• Read our guide → Types of Circuit Breakers in Pakistan

Frequently Asked Questions

What is a 4 Pole MCB?

A 4 Pole MCB is a miniature circuit breaker that protects a three-phase plus neutral (3P+N) circuit by disconnecting all four conductors — L1, L2, L3, and neutral — together on overload or short circuit. The four poles are mechanically linked so a fault on any phase or on the neutral trips all four. This gives complete isolation of the three-phase circuit, essential for main incomers and star-connected loads.

What is the difference between 3 Pole and 4 Pole MCB?

A 3 Pole MCB switches only the three phase conductors. A 4 Pole MCB switches all three phases plus the neutral. Use 3P for circuits without neutral (delta-connected motors) or where the neutral is handled by a separate busbar. Use 4P for three-phase main incomers, solar inverter 3-phase outputs, star-connected loads, and generator changeover panels that need complete isolation.

What size 4 Pole MCB for a three-phase main incomer?

For a typical 3-phase commercial or residential main incomer in Pakistan, use a 63A 4 Pole MCB with 16mm² copper cable. This handles roughly 20-25 HP total load. For larger loads, move to a 4 Pole MCCB rated 100A or higher. Pair the main 4P with a phase sequence relay for phase-reversal protection.

What is the 4 Pole 63A MCB price in Pakistan?

The CNC YCB7-63N 4 Pole 63A MCB is available at Rs.1,900 at CNC Electric Pakistan. Competitor brands: Schneider iC60N 4P 63A typically costs Rs.7,500-10,000, and Chint NB1 4P 63A costs Rs.2,800-3,500. CNC offers equivalent IEC 60898-1 certified performance at a significantly lower price with a 5-year replacement warranty.

Can I use a 4 Pole MCB for my 3-phase solar inverter?

Yes — for the AC output side of a 3-phase solar inverter, a 4 Pole MCB is the correct choice. It ensures the inverter's live and neutral are fully isolated from the house DB during maintenance. Size it at approximately 1.25× the inverter's rated AC output current. For the DC side (panels to inverter), never use an AC MCB — use DC circuit breakers rated for your system voltage (500V, 1000V, or 1500V).

Does the 4 Pole MCB provide motor overload protection?

Partially. The 4 Pole MCB protects the cable and panel against short circuit and trips on sustained overload. It does NOT detect motor-specific issues like stalled rotor, unbalanced phases, or phase reversal. For complete three-phase motor protection, combine this 4P MCB with (a) a thermal overload relay set to the motor FLC, (b) a phase sequence relay, and/or (c) a motor-protection circuit breaker (MPCB) or VFD with built-in motor protection.

What breaking capacity does the CNC 4 Pole MCB have?

6kA at 400V AC per IEC 60898-1. This is adequate for residential, commercial, and small industrial 3-phase panels where the prospective short-circuit current is under 6 kA. For installations close to a large transformer where fault levels exceed 6 kA, move up to a 4P MCCB with 15-50 kA breaking capacity.

How wide is the 4 Pole MCB on the DIN rail?

The CNC YCB7-63N 4 Pole MCB is 72mm wide — four DIN-rail modules. Plan your DB box capacity accordingly: an 18-way DB with one 4P main incomer uses 4 modules, leaving 14 modules for branch circuits (single pole or 1P+N MCBs).