Residual Current Relay Hager CD241J — 30 mA, 2-pole, 40 A

Hager CD241J is a residual current relay designed to detect alternating-current leakage and interrupt power when leakage exceeds 30 mA. As a 2-pole device with a rated switching capacity of 40 A, it is intended for use in single-phase AC distribution circuits where basic residual current protection is required. The relay mounts on standard DIN rails and integrates with protective and switching equipment in residential and light-commercial electrical panels.

Advantages

The device provides sensitive residual current detection at 30 mA, helping reduce the risk of electric shock and minimizing fire hazards linked to earth leakage. Its 2-pole switching arrangement allows protection of both phase and neutral conductors in relevant circuits. With a 40 A switching capacity, the relay can be used with a variety of branch circuits and protective devices while offering consistent trip operation and straightforward installation on DIN rail systems.

Suitable for

• Residential circuit protection where 30 mA residual current detection is required
• Light-commercial electrical installations and small offices
• Integration into distribution boards to add earth leakage protection to specific circuits
• Replacement or upgrade of RCD/RCB functionality in existing panels with compatible space and connections

When it may not be suitable

This relay provides basic residual current protection at a fixed 30 mA sensitivity and is not intended for applications that require adjustable sensitivity, AC/DC immunity characteristics beyond standard alternating-current detection, or very high short-time switching currents. It is not a substitute for combined overcurrent and residual-current devices where coordinated overcurrent protection (such as RCBOs) is required.

Key specifications

• Residual current sensitivity: 30 mA (AC)
• Number of poles: 2-pole
• Rated switching current: 40 A
• Intended use: AC leakage detection and circuit interruption
• Mounting: DIN rail compatible

How to use

Install the relay into the distribution board on a compatible DIN rail and wire the incoming phase and neutral conductors through the device according to the panel wiring diagram and local regulations. Connect the relay’s trip output to the appropriate upstream or downstream switching device as required by the installation. After wiring, test the relay’s operation using suitable test procedures or test buttons on associated devices to verify trip response at the specified leakage level. Ensure power is isolated before performing installation or maintenance.

What to consider before purchase

• Verify that 30 mA residual sensitivity and AC-only detection match the protection requirements for the intended circuits
• Confirm the 40 A switching capacity is sufficient for the connected loads and coordination with upstream protective devices
• Check physical fit and DIN rail space in the distribution board for a 2-pole relay
• Ensure wiring configuration and local electrical codes permit the use of a separate residual current relay in the planned application

Usage recommendations

Use the relay as part of a complete protection scheme: pair with correctly rated upstream overcurrent protection, perform periodic functional tests, and follow local installation standards. For circuits requiring combined overcurrent and residual-current protection or different sensitivity values, select a device that matches those specific requirements.