AC 1 Pole MCB 100A | Reliable Overload Protection

CNC 1 Pole 100A MCB — Heavy-Load Single-Pole Circuit Breaker

The CNC YCB9-125 is a high-ampere single-pole MCB rated at 100A — fitting into the gap between standard household MCBs (which top out around 63A) and bulky MCCBs. It gives you 100A protection in a compact 36mm (2-module) DIN-rail package that fits any standard Pakistani DB box.

Unlike standard 6kA MCBs, this breaker is rated at 10 kA breaking capacity — meaning it can safely interrupt fault currents up to 10,000 amperes. That higher rating is necessary at the 100A level because short-circuit fault currents scale with supply capacity, and installations drawing 100A are usually closer to larger transformers where fault levels are higher.

Typical use in Pakistan: main incoming breaker for large single-phase residential or commercial premises, generator output protection on 15–20 kVA single-phase gensets, and solar inverter AC output protection where the inverter output exceeds the 63A capability of a standard MCB. CNC Electric is a trusted MCB brand in Pakistan with a 5-year replacement warranty.

Specifications

When to Use a 100A MCB Instead of an MCCB

At 100A, you sit at the boundary between the MCB world (up to 125A) and the MCCB world (100A–1600A). The choice between them depends on four factors:

Choose this 100A MCB if: your prospective short-circuit current is below 10 kA (typical for residential and light commercial premises), you want a compact DIN-rail breaker, and you need a fixed C-curve trip. Move to a 100A MCCB if: you are in an industrial environment close to a large transformer, or you need adjustable trip settings for motor coordination.

Where to Use the 100A Single-Pole MCB

Main incoming breaker for a large single-phase home — a house with 4+ air conditioners, electric geyser, EV charger, and large inverter easily draws over 63A. The 100A MCB sits at the top of the DB, with branch 1 Pole MCBs feeding the individual circuits. Pair it with a voltage protector and SPD on the outgoing side.

Single-phase generator output protection — 15–20 kVA single-phase gensets produce roughly 65–87A continuous output. A 100A MCB on the generator's output panel protects the feeder cable and isolates the gen-set for maintenance without needing to move to an MCCB.

Solar inverter AC output — hybrid and off-grid solar inverters rated 15–22 kW single-phase produce roughly 65–96A AC output. The 100A MCB is the standard AC-side protection element on the inverter feeder, positioned between the inverter and the house DB.

Shop or small commercial main breaker — retail outlets, clinics, and small restaurants with high refrigeration and AC loads. Simpler and cheaper than an MCCB where the fault current is under 10 kA.

Large UPS output distribution — 10-20 kVA single-phase UPS systems feeding multiple downstream DB boards.

Important Wiring Notes

Use 25mm² copper cable minimum. 100A continuous current in a 16mm² cable overheats and eventually ignites insulation. The cable is the first thing to fail, not the breaker. For longer runs (over 15 metres) or high ambient temperature, go up to 35mm² cable to allow for voltage drop.

Tighten terminal screws to specification. At 100A, a loose termination generates heat, discolours insulation, and can fuse the terminal into the conductor. Use a torque screwdriver and tighten to 2.5–3 Nm (or whatever the terminal label specifies). Check tightness again after 3 months of service.

Provide panel ventilation. At 100A continuous, the breaker dissipates heat. A closed DB box in a Pakistani summer can exceed 55°C internally, derating the breaker by up to 20%. Either up-size to 125A or provide forced ventilation on installations running near full load.

Pair with a 2 Pole or 4 Pole upstream. For full isolation of both live and neutral (required during maintenance), this 1 Pole breaker should be preceded by a 2 Pole or 4 Pole main isolator. Alternatively, install this 100A MCB on only the live conductor and use a separate 100A neutral link.

Related Products

• Branch circuits (downstream) → 1 Pole MCB 2A-63A (Rs.425)
• Main incomer with neutral switching → 2 Pole MCB 10A-63A (Rs.850)
• Three-phase main incomer → 4 Pole MCB 20A-63A (Rs.1,900)
• Above 100A or industrial fault levels → MCCB breakers 100A-1250A
• Voltage over/under protection → VA Voltage Protector
• Lightning / surge protection → SPD surge protectors
• Earth leakage protection → RCBO breakers
• Automatic WAPDA/generator switching → ATS Automatic Transfer Switches
• Manual WAPDA/generator switching → Changeover switches
• Complete DB setup → DB boxes + breakers
• Read our guide → Types of Circuit Breakers in Pakistan

Frequently Asked Questions

What is a 100A MCB used for?

A 100A MCB is used as the main incoming breaker for large single-phase residential or commercial installations where the total load exceeds 63A — the limit of a standard household MCB. Typical applications include main breaker for a large home with multiple ACs, output protection for 15-20 kVA single-phase generators, AC output of large solar inverters, and main breaker for small commercial premises like shops or clinics.

What cable size do I need for a 100A MCB?

Use 25mm² copper cable as the minimum. For runs longer than 15 metres or in hot environments, step up to 35mm² to allow for voltage drop and cable derating. Never use aluminium cable directly on MCB terminals — if aluminium supply cable arrives, terminate via a bi-metallic lug to copper pigtail at the breaker.

Why is the breaking capacity 10 kA instead of 6 kA?

Breaking capacity has to match the prospective short-circuit current at the point of installation. Standard household circuits (branch level) have fault currents under 6 kA, so 6 kA MCBs are adequate. At the main incomer level drawing 100A, fault currents are typically 8–10 kA, so the 100A MCB is rated at 10 kA to safely interrupt those faults. If your main incomer is close to a large transformer where fault currents exceed 10 kA, move up to a 100A MCCB with 15–50 kA breaking capacity.

What is the 100A MCB price in Pakistan?

The CNC YCB9-125 1 Pole 100A MCB is available at Rs.1,200 at CNC Electric Pakistan. Competitor brands: Schneider iC60N 1P 100A typically costs Rs.4,500–6,000, and Chint NB1 1P 100A costs Rs.1,800–2,200. CNC offers equivalent IEC 60898-1 certified performance with 10 kA breaking capacity at a significantly lower price with a 5-year replacement warranty.

Should I use a 100A MCB or a 100A MCCB?

Use the 100A MCB if your prospective fault current at the installation point is under 10 kA (typical for residential and light commercial premises). Use a 100A MCCB if you are in an industrial environment close to a large transformer (fault level above 10 kA), or if you need adjustable trip settings for motor coordination or selective tripping between main and sub-mains.

Can I use a 100A MCB on a three-phase supply?

No. This is a single-pole MCB for single-phase circuits (230V AC). For three-phase 400V applications requiring 100A protection, use an MCCB rated 100A 3P or 4P, or combine three of these 1-pole MCBs linked mechanically (not recommended for safety reasons — go to the MCCB).

Does the 100A MCB need a separate neutral switch?

Yes — since this is a single-pole breaker, the neutral is not switched. For full-isolation maintenance, install either a separate 100A isolator on the neutral wire, or pair this 1P MCB with a main 2 Pole MCB upstream. In most modern installations, you would use a true 2 Pole MCB at the main incomer if the load is below 63A, and this 100A 1 Pole for heavier loads with a separate neutral isolator.

How much DB space does the 100A MCB occupy?

The CNC YCB9-125 100A MCB is 36mm wide — two DIN-rail modules. That makes it the same width as a 2 Pole MCB, allowing easy substitution in existing DB layouts. Plan your DB capacity: a 12-way DB with this 100A main and 10 branch 1 Pole MCBs uses 2 modules for the main + 10 for branches = 12 total, fitting exactly.