Residual Current Relay Hager CD426J — 4-pole 25 A, 30 mA sensitivity

Hager CD426J is a residual current relay for AC systems with four poles and a rated current of 25 A and a residual-current sensitivity of 30 mA. It is designed to detect earth leakage and initiate circuit interruption to reduce the risk of electric shock and fire. The relay is intended for installation in distribution boards, industrial control panels and residential electrical installations where residual-current protection is required.

Advantages

The device provides reliable detection of alternating earth leakage currents at a 30 mA sensitivity level, enabling timely disconnection of faulty circuits. Its four-pole configuration allows protection of three-phase systems with neutral, and the 25 A rated current matches common branch and load capacities. The relay’s compact form factor facilitates mounting in standard electrical enclosures and panels while maintaining clear functional separation between phases and neutral for safer operation.

Suitable for

• Protection of three-phase mains with neutral in small commercial or industrial panels
• Residual-current protection in residential distribution boards for living spaces
• Use in sub-distribution boards to protect individual circuits or groups of circuits
• Applications where 30 mA sensitivity is required for personal protection against electric shock

When it may not be suitable

This residual current relay is not intended for direct protection of large motors or high-current industrial loads that exceed its 25 A rated current. It is not a substitute for overcurrent protection devices where higher short-circuit or continuous current capabilities are necessary. Additionally, systems requiring other types of residual-current response (for example, DC-sensitive or selective/time-delayed RCDs) should use a device specifically designed for those characteristics.

Key specifications

• Poles: 4 (three phases + neutral)
• Rated current: 25 A
• Residual-current sensitivity (operating threshold): 30 mA
• Type of detection: AC residual current (alternating leakage)
• Intended installation: distribution boards and control panels

How to use

Install the relay in a suitable distribution board or panel according to applicable installation standards and local electrical codes. Connect the three phase conductors and neutral to the corresponding relay terminals, and wire the load circuits through the relay so that leakage currents pass through the sensing element. Ensure proper upstream overcurrent protection and coordinate with other protective devices in the installation. Commissioning should include functional testing by applying a test leakage or using the relay’s test facility, if provided, and verifying correct trip operation and upstream coordination.

What to consider before purchase

• Verify that the 25 A rated current is sufficient for the circuit(s) to be protected.
• Confirm 30 mA sensitivity meets required protection levels for personal safety and local regulations.
• Ensure compatibility with your distribution board layout and terminal wiring arrangement.
• Check whether AC-only sensitivity is adequate or if DC-sensitive or time-delayed residual protection is required.

Usage recommendations

Follow national wiring regulations and manufacturer installation instructions. Coordinate the relay with appropriate upstream overcurrent protection, perform routine testing after installation, and include the device in periodic safety inspections to ensure continued residual-current protection performance.