MCB Circuit Breaker: Complete Guide — Types, Sizes & Prices in Egypt
The MCB (Miniature Circuit Breaker) is the foundation of every distribution panel — it protects wires and appliances from overload and short circuits. But choosing the right size and curve for each circuit is what separates a professional panel from one with real gaps.
By the Ases Kahraba team — Last updated: March 2026
Quick Answer
MCB 16A for lighting, 20A for sockets, 32A for AC — the correct sizing table. B/C/D trip curves explained, trusted brands in Egypt, and why MCB alone isn't enough protection.
Everything You Need to Know About MCB Breakers
- How does an MCB work? It relies on two mechanisms: (1) Thermal protection — a bimetallic strip heats and bends under sustained overload, tripping the circuit. (2) Magnetic protection — an electromagnetic coil trips instantly during a sudden short circuit. The difference is speed: short circuit = trip in milliseconds, overload = trip in seconds to minutes depending on severity.
- Trip curves B / C / D — the critical difference: Curve B (trips at 3–5× rated current): for lighting and electronics. Most sensitive. Curve C (trips at 5–10× rated current): most common for general outlets, AC units, and small motors. Curve D (trips at 10–20× rated current): for large motors and high inrush-current loads. In residential apartments: C is the default for most circuits.
- Correct ampere sizes per circuit: 6A — general lighting (1.5mm² wire). 10A — lighting with small fans. 16A — general outlets in living rooms and bedrooms (2.5mm² wire). 20A — kitchen outlets, washing machine, oven. 25–32A — large split AC unit (4–6mm² wire). 40–63A — apartment main breaker. Warning: never upsize the breaker beyond the wire's capacity — fires start in the wires, not the breaker.
- Best MCB brands in the Egyptian market 2026: Schneider Easy9 — most widely available, reasonable price (EGP 15–35/unit). Warning: high counterfeiting rate — verify serial numbers on Schneider's website. Legrand DX3 — higher quality and price (EGP 40–90). ABB SH200L — high reliability for large projects. Siemens 5SL — available at major distributors. Avoid: unbranded breakers from El-Ataba — they may fail to trip when actually needed.
- MCB protection limits — what it cannot do: An MCB does not protect people from electric shock. The breaker only trips when current exceeds its rated value — the earth leakage that shocks a person (30mA) is far below any MCB's trip threshold. Solution: add an RCCB or use RCBO per sensitive circuit (bathroom, kitchen, outdoor).
- Installing an MCB in the distribution panel: the breaker snaps onto the DIN rail. Direct wire connection: live wire (red/brown) to the upper terminal (Line in), outgoing circuit wire (Load out) to the lower terminal. Screws must be tightened to the correct torque (1.5–2.5 Nm) — a loose screw causes thermal arcing and fire.
Table: Recommended Ampere Size per Use
| Circuit Use | Breaker Size | Wire Size | Curve |
|---|---|---|---|
| Lighting | 6A | 1.5mm² | B/C |
| General Outlets | 16A | 2.5mm² | C |
| Kitchen / Washer | 20A | 2.5mm² | C |
| AC 1.5–2 HP | 25–32A | 4–6mm² | C |
| Apartment Main | 40–63A | 10–16mm² | C |
Frequently Asked Questions
What is the difference between MCB, RCCB, and RCBO?
MCB protects from overload and short circuits only. RCCB protects from earth leakage (electric shock) but doesn't protect from overload alone. RCBO combines both functions in one breaker — best for sensitive circuits (bathrooms, kitchens). For full details read: Complete Breaker Types Guide.
Why does my MCB keep tripping even with no obvious overload?
Possible causes: (1) The breaker itself is internally faulty (especially if old or unbranded). (2) Intermittent short circuit in the wiring or a connected appliance. (3) The actual circuit load marginally exceeds the breaker's rating. (4) High panel temperature causes the thermal protection to trip early. Solution: replace the breaker first, and if tripping continues investigate the circuit.
Can I replace a 16A breaker with a 20A to stop it tripping?
No — this is a common and dangerous mistake. The breaker trips because the wires can't handle the load. Raising the breaker rating means the wires will overheat more than necessary without the breaker tripping — causing a wire fire. Correct solution: reduce the load or run a new circuit with a larger cross-section.
How do I verify that a Schneider Easy9 is genuine and not counterfeit?
Verification methods: (1) Serial number on the side label — verify it on the Schneider website or Trace app. (2) Weight — genuine breakers are slightly heavier than fakes. (3) Printed text on the body is clear and uniform. (4) A price below EGP 12 per unit is suspicious. (5) Buying from an authorized distributor or EPEMall is safer than El-Ataba market.
How many MCBs does a 3-bedroom apartment need?
A typical 3-bedroom apartment needs: 1 lighting breaker (6–10A) per room = 4–5 breakers. 1 outlet breaker (16A) per room = 4–5 breakers. 1–2 kitchen breakers (20A). 2–3 AC breakers (25–32A). 1 main breaker (40–63A). Total: 12–16 panel positions. Add a shared RCCB or RCBO per wet circuit.
Does a cheap Chinese breaker work as well as Schneider?
No. Unknown-brand breakers may misread current levels — tripping under normal loads (annoyance) or failing to trip during a real fault (fire). The price difference of EGP 5–10 per breaker is not worth the risk. Invest in a trusted brand with traceable serial numbers.