BG Bi-Directional MCB B Curve Single Pole 40A CUMB40

BG CUMB40 — 40A B Curve Single-Pole Bidirectional MCB (6kA, 1 Module)

The BG CUMB40 is a 40A B-curve single-pole bidirectional MCB engineered for reliable overload and short-circuit protection on medium-to-high load domestic and light-commercial circuits. Its bidirectional operation ensures safe performance even in systems where current may flow in either direction, including installations incorporating solar PV, battery storage or microgeneration.

With its compact 1-module 17.85mm width, the CUMB40 integrates cleanly into BG consumer units and DIN-rail enclosures, making it ideal for both new installations and upgrade work.

Robust Protection for Higher-Demand Circuits

The B-curve tripping characteristic makes the CUMB40 suitable for circuits with low inrush currents, delivering fast, reliable fault disconnection. A 6kA breaking capacity ensures safe interruption of short-circuit conditions across a wide range of residential and small-commercial applications.

Typical uses include:

High-load radial circuits

Small sub-mains and distribution feeds

Heating and immersion systems

Utility circuits and fixed appliances

Installer-Friendly & Built for Longevity

Designed for long-term dependability and straightforward installation, the CUMB40 features:

Positive contact status indication

PZ2 screw terminals

Up to 25mm² terminal capacity (for 32–55A models)

Reliable operation from –25°C to +40°C

4,000 electrical and 10,000 mechanical endurance cycles

The result is a durable, contractor-approved protective device suitable for high-demand installations.

Key Features of the BG Bi-Directional MCB 40A Include:

• 40A B-Curve Single-Pole Bidirectional MCB
• Ideal for PV, Battery Storage & Back-Feed Capable Installations
• 6kA Breaking Capacity for Reliable Fault Disconnection
• Compact 1-Module (17.85mm) DIN-Rail Design
• Positive Contact Status Indication
• PZ2 Screw Terminals with Up to 25mm² Cable Capacity
• Operating Temperature Range: -25°C to +40°C
• Durable Mechanism: 4,000 Electrical & 10,000 Mechanical Operations
• Complies with IEC/EN 60898 Standards

View all BG MCBs

If you just need some help, would like to take advantage of our Price Promise or perhaps have a large order to place give our team of professionals a call on 0203 994 5470, drop us an email at sales@electricpoint.com or use our Contact Form.