HUM18-125 MCB Circuit Breaker – 63A-125A

HUM18-125 MCB Circuit Breaker 125 A – High-Current Protection for Main and Sub-Main Circuits

If a standard 63 A or 40 A MCB Circuit Breaker does not satisfy the requirements, then/when applicable, the HUM18-125 steps in to satisfy with a 125 A rating and a Icu 10 kA/Ics 7.5 kA breaking capacity. The HUM18-125 is an ideal application for the main circuit breaker in commercial distribution boards, sub-main circuit breaker in industrial panels, or dedicated feeder to support high-demand equipment at 400 V AC (50/60 Hz). The HUM18-125 meets with IEC 60898-1 standards and is CCC, CB, and CE certified for acceptance in the global marketplace.

The HUM18-125 is built in 1P, 2P, 3P, and 4P versions and is offered in Type B, C and D curves across the 63 A, 80 A, 100 A and 125 A ratings, fulfilling the upper end of MCB miniature circuit breaker applications. The terminal connections on the HUM18-125 will accommodate up to 50 mm² conductors at 3.5 N·m of torque, as is required for the cable sizes used with 100 A and 125 A circuits. For panel builders and project contractors, this MCB delivers the performance typically associated with premium-brand-MCB products at factory-direct OEM/ODM pricing from HUYU Electric, making it a comparable alternative to Schneider, ABB, Hager, Eaton, Siemens, Legrand, and Chint, for high-current MCB circuit breaker applications.

Pole Types & MCB Circuit Breaker Ratings from 63A to 125A

All four types of pole configurations will operate with the same Icu 10kA / Ics 7.5kA breaking capacity. Type B will trip at 3 to 5 times In for resistive loads; type C will trip at 5 to 10 times In for inductive loads such as HVAC compressors and pumps; type D will trip at 10 to 20 times In for high inrush type loads such as large transformers and motor startups. The MCB circuit breaker at 63-125 amperes comes in 4 steps, allowing you to size precisely to the load rather than selecting one option that is oversized.

Where HUM18-125 Is Used – Main Breakers, Sub-Mains & High-Current Equipment

MCB circuit breakers at this level of current are designed primarily to protect feeder cables, but also provide isolation for the larger zones of an installation. In commercial buildings, a 3-phase 125 ampere MCB can serve as the main supply for a floor distribution board. In factories, it can be used for machine feeds or to provide power to subpanels serving multiple motor circuits. The HUM18-125 is located upstream from smaller kinds of MCBs designed for protection of individual final circuits and therefore is designed to handle larger short-circuit current ratings and larger conductors, having 50 sq mm terminals and 3.5 N-m of torque. Panel builders choosing between MCBs and Circuit Breaker devices will find the HUM18-125 offers the convenience of being a DIN-Rail mounted device but the current rating typical for a molded-case circuit breaker.

Technical Specifications

OEM/ODM Supply – A 125A MCB Circuit Breaker Alternative for Volume Buyers

Buyer’s Guide

Selecting the Right 125A MCB Circuit Breaker – Rating, Curve & Application

A practical guide to specifying the correct HUM18-125 for main and sub-main circuits.

1. Choosing the Current Rating

The HUM18-125 spans 63A to 125A in four steps: 63A, 80A, 100A, and 125A. For a main breaker in a small commercial panel, 80A or 100A is typical. For sub-main feeds to larger equipment or floor distribution, 100A or 125A. Always size the MCB to the cable cross-section: at 100A you will need at least 25mm² copper; at 125A, 35mm² or 50mm² depending on installation conditions. The HUM18-125 terminals accept up to 50mm², so conductor sizing is never limited by the device.

2. Trip Curve – B, C, or D at High Current?

At 125A, the trip curve choice is driven by the load type downstream. Type B (3–5× In) is less common at this current — mainly for purely resistive heating banks. Type C (5–10× In) is the default for general commercial distribution. Type D (10–20× In) is needed when the breaker supplies a motor control center or transformer primary with high inrush. The tripping curve chart above shows the exact time‑current response for all three types.

3. 1P, 2P, 3P, or 4P?

1P for single-phase main breakers up to 125A. 2P for 400V isolation in split-phase or single-phase systems. 3P is the standard choice for three-phase distribution. 4P adds neutral disconnection where local codes require it. All four pole variants keep consistent per-pole dimensions, so panel layout stays uniform regardless of the configuration chosen.

4. Installation Notes

The HUM18-125 mounts on a standard TH35-7.5 DIN rail with top or bottom incoming. Terminal torque is 3.5 N·m — higher than smaller MCBs — reflecting the mechanical force required for secure 50mm² connections. Operating range is -5°C to +45°C, suitable for indoor and sheltered outdoor panels. As a main breaker, it is designed for infrequent operation: 4,000 electrical and 8,000 mechanical cycles at rated current. For circuits requiring frequent daily switching, consider a contactor in combination with this MCB for protection.

Frequently Asked Questions

What are the four types of MCB?

The four common MCB circuit breaker types are defined by their trip curves: Type B (trips at 3–5× rated current, for resistive loads), Type C (5–10×, for inductive loads like motors and HVAC), Type D (10–20×, for high-inrush equipment such as transformers and large motors), and Type A/K (for semiconductor protection, less common in general distribution). The HUM18-125 is available in Type B, C, and D.

Can a bad MCB cause a fire?

Yes. An MCB circuit breaker that fails to trip during an overload or short circuit can allow excessive current to flow through wiring, generating heat that may ignite surrounding materials. This is why quality certification (such as IEC 60898-1, CCC, CB, and CE on the HUM18-125) and proper installation torque (3.5 N·m on this device) are critical — loose connections inside a breaker can also cause localized overheating. Routine testing and replacement at the end of service life reduce this risk.

Are MCB and circuit breaker the same?

An MCB (Miniature Circuit Breaker) is one type of circuit breaker. The broader category includes MCCBs (Moulded Case Circuit Breakers) for higher currents, ACBs (Air Circuit Breakers) for main switchboards, and RCDs/RCBOs for earth leakage protection. When comparing MCB vs circuit breaker, the MCB is the compact, DIN-rail-mounted device used in final distribution panels — which is exactly what the HUM18-125 is, despite its higher 125A rating.

Is MCB used in AC or DC?

MCBs are available for both AC and DC circuits, but a specific device is designed for one or the other — an AC MCB should not be used on DC, and vice versa. The HUM18-125 is an AC MCB circuit breaker rated for 50/60Hz systems. The Type field in the specification table confirms this: it is Type AC. For DC applications such as solar PV strings or battery banks, a dedicated DC-rated MCB is required.