Residual Current Circuit Breaker ABB FH204 AC-40/0.03 40 A 4P

ABB FH204 AC-40/0.03 is a residual current circuit breaker that combines overcurrent protection with earth-leakage detection in a single 4-pole device. Rated for 40 A and with 30 mA residual current sensitivity, this RCBO-style device is designed to detect AC-type leakage currents and interrupt supply to protect people and equipment in TN and IT distribution systems. It is intended for integration into residential, commercial and light industrial distribution boards where combined short-circuit, overload and earth-leakage protection is required.

Advantages

The ABB FH204 AC-40/0.03 provides coordinated overcurrent and residual current protection in one compact unit, reducing the number of devices and simplifying wiring in distribution panels. With a 4-pole construction it ensures simultaneous disconnection of all conductors including neutral in three-phase systems. The 30 mA sensitivity helps reduce the risk of electric shock to users while the device’s rated 40 A capacity meets typical feeder and circuit loads in small commercial and residential applications. Installation is compatible with standard DIN-rail mounting and common distribution board layouts.

Suitable for

• Residential main and sub-distribution boards where earth-leakage protection is required
• Small commercial premises and offices protecting three-phase circuits and appliances
• Light industrial distribution where coordinated overload and leakage protection is needed

When it may not be suitable

This device is specified to respond to AC-type residual currents at 30 mA sensitivity; it may not be suitable for installations where detection of pulsating DC or mixed-frequency leakage currents is required unless the system is verified as compatible. The 40 A rated current limits its use on circuits that routinely carry higher continuous currents; larger feeders will require devices with higher current ratings.

Key specifications

• Poles: 4-pole (simultaneous disconnection of all conductors)
• Rated current: 40 A
• Residual current sensitivity: 30 mA (0.03 A)
• Residual current type: AC (designed to detect alternating leakage currents)
• Intended systems: TN and IT earthing systems
• Mounting: DIN-rail compatible for distribution boards

How to use

Mount the ABB FH204 AC-40/0.03 on a standard DIN rail inside a suitable distribution board and connect line and load conductors according to the electrical schematic of the installation, ensuring correct phase and neutral arrangement for four-pole operation. Verify proper tightening of terminals and that the device is accessible for manual testing. After wiring, apply supply and perform the built-in test routine and any external insulation and continuity checks required by local regulations. Regularly test the residual current function according to maintenance schedules to confirm continued protection.

What to consider before purchase

• Verify that 40 A rated current is suitable for the intended circuit load
• Confirm that AC-type residual current sensitivity (30 mA) meets local safety requirements and the types of leakage expected
• Ensure compatibility with the distribution board space and DIN-rail mounting
• Check that simultaneous disconnection of neutral is acceptable for the installation

Usage recommendations

Install and commission the device in accordance with local electrical codes and manufacturer installation instructions. Perform periodic functional tests of the residual current trip mechanism and incorporate the device into the facility’s preventive maintenance programme to ensure reliable protection against electric shock and leakage faults.