ABB BMFW440/AC300 4-Pole 40A 300mA RCCB
The BMFW440/AC300 is a 4-pole 40A residual current circuit breaker (RCCB) with a 300mA AC-type sensitivity from ABB's Formula DIN Rail range. It protects people and installations against earth fault currents and is manufactured to IEC standards, making it suitable for three-phase distribution boards across UAE residential, commercial, and light industrial installations.
Key Features
- 4-pole configuration for three-phase and neutral circuit protection against earth leakage faults
- 300mA AC-type sensitivity suitable for general protection against fault currents in standard distribution circuits
- Rated operational voltage of 230/400V with a 4kV rated impulse withstand voltage for reliable insulation performance
- IP20 degree of protection with an operating temperature range of -25°C to +55°C, suited to UAE ambient conditions
- Genuine ABB Formula Din Rail quality — rated for 10,000 electrical and mechanical operating cycles
Technical Specifications
| Specification |
Details |
| Brand |
ABB |
| Model |
BMFW440/AC300 |
| Type |
RCCB (ELCB) |
| Poles |
4 |
| Rated Current (In) |
40A |
| Sensitivity |
300mA |
| Input Voltage Type |
AC |
| Rated Voltage (Ur) |
230/400V |
| Rated Impulse Withstand Voltage (Uimp) |
4kV |
| Rated Frequency |
50Hz |
| Degree of Protection |
IP20 |
| Mounting |
DIN Rail |
| Connecting Capacity |
Flexible 35mm² / Solid 25mm² |
| Electrical & Mechanical Endurance |
10,000 cycles |
| Ambient Operating Temperature |
-25°C to +55°C |
Applications
- Earth fault protection for three-phase distribution boards in villas and commercial buildings
- Main incomer protection for sub-distribution boards in FM-managed facilities
- Fault current protection for HVAC and pump motor circuits in commercial installations
- General earth leakage protection in retail, warehouse, and light industrial panels across the UAE
FAQ
-
What's the difference between an MCB and an RCCB/RCD?
An MCB protects circuits and wiring against overload and short-circuit current. An RCCB like this one protects against earth leakage by monitoring current imbalance and disconnecting the circuit — the two are complementary and are normally installed together in a distribution board.
-
What does the 300mA sensitivity rating mean?
300mA RCCBs are sized for fire and equipment protection on larger circuits and sub-mains, not personal shock protection — that requires a 30mA device. A 300mA unit is a common choice as a main incomer or sub-distribution protection device upstream of 30mA final-circuit RCDs.
-
How many poles do I need?
A 4-pole (4P) RCCB switches all three phases plus neutral together. Use 4P for three-phase supplies or distribution boards where the neutral must also be isolated; 2-pole devices are used for single-phase circuits.
-
Can this be used alongside MCBs in the same board?
Yes. This RCCB is typically installed upstream of the MCBs it protects, on the same DIN rail, so a leakage fault trips the RCCB while overloads/short circuits are still cleared by the individual MCBs.
-
Can I install this myself?
No. RCCBs are wired into a live distribution board and must be installed by a licensed electrician in line with UAE wiring regulations.
