Legrand DX3 MCB Selection Guide: Which Breaker for Each Circuit in a House

A house needs one incomer (a DX3 double-pole isolator or SPN MCB), one 30 mA double-pole RCCB, and one single-pole C-curve DX3 MCB per circuit: 6 A for lighting, 16 A for socket circuits, 20 A for a geyser or 1.5-ton AC, 25 A for a 2-ton AC, sized to the wire behind it. Every DX3 single pole from 6 to 32 A costs the same ₹494 MRP, so the right rating never costs more than the wrong one.

Rating: match the wire, not the load

An MCB protects the wire, so its rating must not exceed what the wire can carry: 1.5 sq mm takes a 10 A breaker at most, 2.5 sq mm 16 to 20 A, 4 sq mm 25 A, 6 sq mm 32 A. Within that limit choose the rating that comfortably covers the load. The MCB selector works it out from watts and wire size, and the wire size guide gives the wire behind each circuit.

Struck-through figures are Legrand MRP per unit inclusive of GST, Corp MPL 2026. Bold figures are Mount Cable India's price at 65% off MRP, one of the highest Legrand discounts in Bangalore, on every Legrand product.

Poles

Outgoing circuits in a single-phase home use single-pole MCBs; the neutral runs through the neutral bar. The incomer is double pole so both live and neutral are broken, which is why a DP isolator or an SPN MCB sits at the head of the board. Three-phase homes and buildings use TP or TPN MCBs and FP RCCBs, in an ETPN or vertical TPN Ekinox board.

Curve

C curve for everything in a house: lighting, sockets, ACs, geysers, ovens. D curve only where a motor's starting current keeps tripping a C-curve breaker, typically a borewell pump or a lift. D curve costs more (₹678 against ₹494 for a single pole) and gives less protection against small overloads, so it is not a default.

RCCB sensitivity and type

30 mA for shock protection, which is what a home needs; 100 mA and 300 mA are upstream fire-protection devices for larger installations. AC type for a standard home. HPI type if the house runs a solar inverter, a large UPS or a lot of electronics, because those cause nuisance trips on AC-type RCCBs; the HPI 40 A DP is ₹12,271 against ₹6,360 for the AC type. Type S only where one RCCB must coordinate with another downstream. The MCB, RCCB and RCBO guide has the reasoning.

RCBO or RCCB plus MCBs

An RCCB for the board plus an MCB per circuit is the standard and the cheapest. A DX3 RCBO (₹6,974 for 6 to 32 A DP at 30 mA) combines both in one device for one circuit, so a leak on that circuit trips only that circuit. It is worth it for the geyser, an outdoor circuit or a home office, not for every circuit.

Counting the board

List the circuits, add two spare ways, and that is the Ekinox SPN size: 8 way for a 2BHK, 12 way for a 3BHK, 16 or 18 way for a large house. IP43 with a metal door is the normal indoor choice at ₹4,065 (8 way) and ₹4,884 (12 way). The whole board costed at MRP is on Legrand MCB best price, and the DB selection guide covers the board itself.

Get your Legrand price. WhatsApp the list, the DB schedule or a photo of the electrician's memo to 88676 76700. Mount Cable India replies with an itemised Legrand quote within 60 minutes, and you can use it as a reference price anywhere in Bangalore. No obligation to buy from us.