Choose an MCB rated at or just above the circuit's normal current, but never above what the wire can carry. Use a C curve for most circuits, B for lighting and D for motors. Use DP (2 pole) where both phase and neutral must switch off, such as for an AC or geyser.
Typical MCB ratings for a home or shop
| Circuit | Typical load | MCB | Copper wire |
|---|---|---|---|
| Lighting and fans | up to about 1 kW | 6 A or 10 A, B curve, SP | 1.5 sq mm |
| Power sockets (16 A) | up to about 3 kW | 16 A, C curve, SP | 2.5 sq mm |
| Geyser, 2 kW | about 8.7 A | 16 A, C curve, DP | 2.5 sq mm |
| Geyser, 3 kW | about 13 A | 20 A, C curve, DP | 4 sq mm |
| Split AC, 1.5 ton | about 7–8 A running | 16 A, C curve, DP | 2.5 sq mm |
| Split AC, 2 ton | about 9–10 A running | 20 A, C curve, DP | 4 sq mm |
| Three-phase distribution | depends on load | TP or 4 pole, C curve | as per load |
1. The rating (amps)
Work out the current: for a single-phase load, current ≈ watts ÷ 230. A 2 kW geyser draws about 2000 ÷ 230 = 8.7 A, so a 16 A MCB suits it. The MCB protects the wire, so its rating must never be higher than the wire's safe current. If you need a bigger MCB, you need a bigger wire too.
2. The trip curve (B, C or D)
| Curve | Trips instantly at | Use for |
|---|---|---|
| B | 3 to 5 × rated current | Lighting and resistive loads such as heaters |
| C | 5 to 10 × rated current | General circuits, sockets, ACs, small motors: the usual choice |
| D | 10 to 20 × rated current | Motors, transformers, welding sets and loads with high starting current |
3. The number of poles
| Type | Poles | Use |
|---|---|---|
| SP | 1 pole | Single-phase circuits, switching the phase only |
| DP | 2 pole | Single-phase, switching phase and neutral: AC, geyser, incomer |
| TP | 3 pole | Three-phase loads without neutral, such as motors |
| TPN / FP | 3 pole + neutral / 4 pole | Three-phase distribution with neutral |
4. Breaking capacity
This is the largest fault current the MCB can safely break, marked in kA. 6 kA suits most homes; 10 kA is the usual choice for commercial buildings and industry, especially close to a large transformer.
Add an RCCB for shock protection
An MCB does not protect people from electric shock. Add a 30 mA RCCB on the incoming supply, or on wet-area circuits such as the bathroom and kitchen. 100 mA and 300 mA RCCBs are used for fire protection on larger installations.
MCBs and RCCBs we supply
- All MCBs & RCCBs
- L&T (Lauritz Knudsen) Exora MCB
- Schneider Acti9 xC60 MCB
- Siemens Betagard 5SL6 MCB
- RCCBs: L&T, Schneider, Siemens
Need help choosing?
Send us the rating, the load or a photo of the nameplate on WhatsApp, and we will confirm the right model, availability and rate.
Values are typical guidance for Indian 230 V single-phase and 415 V three-phase supplies. Always follow the equipment nameplate, the manufacturer's instructions and your licensed electrician, who is responsible for the final selection and installation.