Residual-current circuit breaker Polot CDC240J 2P 40A 30mA Type AC

The Polot CDC240J residual-current circuit breaker (RCD) is a 2-pole protective device rated for 40 A with 30 mA sensitivity and Type AC detection. It monitors differential current between live and neutral conductors and disconnects the circuit if alternating earth leakage above the set threshold is detected. The device is intended to improve electrical safety in residential and light commercial installations by reducing the risk of electric shock and limiting fire hazards related to insulation faults and leakage currents.

Advantages

This 2P 40A 30mA Type AC RCD provides reliable AC-only leakage detection and fast disconnection at the rated sensitivity, making it suitable for general circuit protection. The compact design allows DIN-rail mounting and integration into standard distribution boards. The 30 mA trip level balances user safety for protection against harmful electric shock while avoiding unnecessary trips from small leakage currents common in typical household and light commercial equipment.

Suitable for

• Protection of lighting and socket circuits in homes
• Safety protection for small workshops and light commercial premises
• Circuits supplying fixed appliances that do not require Type A or Type B detection
• Retrofit projects where space for a compact 2-pole device is needed

When it may not be suitable

The CDC240J is a Type AC device and detects only sinusoidal alternating residual currents. It may not be suitable where pulsating DC or high-frequency leakage currents are present, or where appliances generate DC components that require Type A or Type B protection. It also does not provide overcurrent protection by itself, so it should be used in combination with appropriate circuit breakers or fuses for overload and short-circuit protection.

Key specifications

• Number of poles: 2 (2P)
• Rated current: 40 A
• Residual operating current: 30 mA
• Residual current detection type: AC (sinusoidal alternating currents)
• Mounting: DIN-rail compatible (standard distribution board mounting)
• Trip characteristic: instantaneous residual current operation at rated sensitivity

How to use

Install the CDC240J in the consumer unit on a standard DIN rail and connect the line and neutral conductors to the designated terminals according to local wiring regulations. Ensure the device is installed upstream of the circuits requiring residual current protection and downstream of overcurrent protective devices if separate overload protection is used. After wiring, test the RCD using its test button (if fitted) or an external RCD tester to confirm correct operation before placing the circuit into normal service. Periodic testing is recommended to verify continued functionality.

What to consider before purchase

• Confirm that Type AC residual current detection is appropriate for the connected loads.
• Verify the 40 A rated current matches the intended circuit load and downstream protective devices.
• Ensure compatibility with the available DIN-rail consumer unit space and terminal wiring sizes.
• Plan for separate overcurrent protection if not integrated into the same device.

Usage recommendations

Use the CDC240J where reliable AC-only leakage protection is required for general-purpose circuits. Combine it with correctly sized circuit breakers or fuses for comprehensive protection, and perform regular test checks to ensure continued residual-current detection performance.