Miniature circuit breakers (MCBs) are the workhorses of low-voltage distribution. Picking the wrong rating either nuisance-trips your loads or — worse — fails to protect them in a fault. This guide walks through the four decisions every MCB selection comes down to and the cross-brand part-number patterns to look for.
Step 1: Determine the load current
Start with the full-load current of the circuit (continuous draw, NOT inrush). The MCB rated current (In) should be ≥ this value with a small margin. Typical UAE residential lighting circuits sit at 6A or 10A; receptacles 16A or 20A; small motors and air-conditioning circuits 25A or 32A; sub-distribution feeders 40A to 63A.
Step 2: Choose the breaking capacity (Icn / Icu)
Breaking capacity is the maximum prospective short-circuit current the MCB can interrupt without exploding. For most domestic and light-commercial UAE panels downstream of a transformer, 6 kA is sufficient. Industrial sub-boards near the incomer typically need 10 kA; main distribution close to the substation may require 15 kA or 25 kA. Always size for the worst-case fault current at the MCBs position — never guess.
Step 3: Pick the trip curve (B, C, D, K)
The curve defines the multiple of rated current at which the magnetic (instantaneous) element trips:
- Curve B (3–5×In): Resistive loads, lighting, residential socket circuits.
- Curve C (5–10×In): General-purpose mixed loads, light motors, fluorescent. The default for most commercial installations.
- Curve D (10–20×In): High-inrush loads — motors, transformers, capacitor banks.
- Curve K (8–14×In): Specialised; small motor protection (used by some brands as the motor-grade curve).
Step 4: Number of poles
Single-pole (1P) for single-phase line; 1P+N for line + switched neutral (UAE-compliant for socket circuits where the regulation requires neutral disconnection); 2P, 3P, 3P+N, 4P for higher-phase or motor circuits.
Cross-brand part-number patterns
How do I read an ABB MCB part number?
ABBs S200 / S280 / S290 series: format like 2CDS251001R0064 where the embedded “06” is the rated current (6A) and “1” is the pole count. The S200 prefix tells you its a 6 kA breaker. Higher-spec series include S280 (10 kA) and S290 (15 kA).
How do I read a Schneider Electric MCB part number?
Schneiders iC60 / Acti9 / DOMA series codes embed the breaking capacity and rated current. For example A9F74616 = iC60N (6 kA) C-curve 16A 1P. The leading “A9F” plus the trailing digits decode current + poles + curve.
What about Hager and Legrand?
Hager uses prefixes like MC (residential) and MZ (industrial); Legrand uses DX³ family codes. Both follow similar conventions — current + poles + curve embedded in the suffix. Browse our brand pages for the full reference tables.
Quick reference table
| Application | Recommended Curve | Typical In (A) | Typical Icn (kA) |
|---|---|---|---|
| Lighting circuit | B | 6 – 10 | 6 |
| General receptacles | C | 16 – 20 | 6 – 10 |
| Air-conditioning | C | 20 – 32 | 10 |
| Motor (DOL) | D | 16 – 63 | 10 – 15 |
| Distribution feeder | C / D | 40 – 125 | 15 – 25 |
Sourcing
EPFINDER stocks the full S200, iC60, MC, and DX³ ranges in our Dubai warehouse, plus equivalents from Eaton, Legrand, Hager, Lovato, and Chint. Browse in-stock MCBs or request a project quote.
