What MCB rating for a 1.5 ton AC?

A 1.5 ton split AC draws ~8-10A continuous. Use a 16A C-curve MCB on a dedicated circuit. C-curve handles the compressor inrush surge. 2.5 sqmm copper wire is the matching cable.

A 2 kW storage geyser needs a 16A B-curve MCB on 2.5 sqmm copper. A 3 kW instant geyser needs a 20A or 25A B-curve MCB on 4 sqmm copper. Always pair with a 30 mA RCCB for shock safety in wet zones.

B-curve vs C-curve MCB — what's the difference?

B-curve trips at 3-5× rated current. Use for resistive loads (geyser, heater, lighting, sockets). C-curve trips at 5-10× rated current. Use for inductive loads (AC, motor, fridge, pump) that have a starting surge. C-curve is the most common all-purpose MCB.

What MCB for kitchen circuit?

Modern kitchens with mixer + induction + microwave + fridge can pull 16-20A combined. Use a dedicated 20A or 25A C-curve MCB on 4 sqmm copper. Run a separate 16A circuit for fridge so kitchen trips don't spoil food.

← All tools Home

Free Calculator · India

MCB Rating Calculator — Pick the Right Amperage & Curve

Find the correct MCB amperage and curve type (B / C) for AC, geyser, motor, kitchen and lighting circuits. Built for Indian 230V single-phase homes and small offices. Tool follows IEC 60898-1 standard MCB ratings.

Calculator

Appliance / Circuit type

Or enter custom load (watts)

Load type

Supply

Standard MCB ratings (IEC 60898-1)

MCB rating	Typical use	Recommended wire	Curve
6 A	LED lighting circuits, fan circuits	1.0 / 1.5 sqmm copper	B
10 A	5A power sockets, small appliances	1.5 sqmm copper	B / C
16 A	16A power sockets, geyser 2 kW, AC 1-1.5 ton	2.5 sqmm copper	C (for AC), B (for geyser)
20 A	Kitchen circuits, microwave, instant geyser	2.5 / 4 sqmm copper	C
25 A	2 ton AC, large kitchen, EV charger	4 sqmm copper	C
32 A	2 HP motor, sub-DB feeder	6 sqmm copper	C / D (for motor)
40 A	Service incoming for small flat	10 sqmm copper	C
63 A	Service incoming for 3 BHK / shop	10 / 16 sqmm copper	C

For three-phase distribution, divide single-phase amps by 3 (per pole). Always pair MCBs with a 30 mA RCCB upstream for earth-leakage protection in wet/outdoor zones.

Frequently asked

What is the difference between B-curve and C-curve MCB?

B-curve trips at 3-5× rated current — use for resistive loads (geyser, lighting, sockets, heater). C-curve trips at 5-10× rated current — handles starting surges of motors, AC compressors, fridges. C-curve is the most common all-purpose MCB.

Do I need RCCB or just MCB?

You need both. MCB protects wiring from overcurrent + short circuit. RCCB protects YOU from earth-leakage shock. Modern installations use a 30 mA RCCB upstream feeding multiple MCBs (one MCB per circuit).

Which MCB brand is best in India?

For Chennai we recommend Anchor by Panasonic, Legrand, Altech and Lauritz Knudsen. See our MCB dealer page in Sowcarpet or MCB DB dealer page.

Can I use a 32A MCB on 1.5 sqmm wire?

No — that's dangerous. The wire would melt before the MCB trips. Always match: 1.5 sqmm → max 13A; 2.5 sqmm → max 20A; 4 sqmm → max 25A. Use our wire size calculator to confirm.

Need MCB delivered today?

Anchor by Panasonic, Legrand, Altech, Lauritz Knudsen — all in stock at Sowcarpet. Same-day delivery, GST invoice, contractor pricing.

WhatsApp MCB quote All dealer pages