A 4-pole 40A circuit breaker (MCB) protects heavy-duty three-phase circuits in a home or small business, usually the supply to a sub-distribution board. The three phases are protected, the neutral is switched with them, and in the event of a fault all poles open together.
When do you choose 40 A per phase?
- supplying a three-phase sub-distribution board
- an outbuilding, workshop or consulting room with its own distribution board
- a three-phase appliance rated at 40 A per phase
A neutral conductor is a prerequisite, so this version suits a 3N×400 V supply. As for the cable: in homes, AREI (the Belgian electrical installation regulations) requires at least 6 mm² for 40 A, and long supply cables are often given a larger cross-section to limit voltage drop.
Benefits
- selectivity with upstream fuses according to Schrack's tables
- back-up fuse up to 80 A gG
- open contacts are at least 4 mm apart, so the circuit is safely isolated
- 4 modules wide
Installation
A supply cable carrying 40 A per phase requires solid connections: the BMS4 accepts conductors up to 25 mm², and Schrack specifies a tightening torque of 2 to 2.4 Nm. With a cover fitted, it achieves IP40 in the consumer unit.
Good to know
The sub-board fed by this MCB needs its own MCBs and residual current devices (RCDs). Design and installation are a job for a qualified electrician; the extension must then be inspected by an approved inspection body, as AREI requires.
| Product code | BM417840 (Schrack BMS4 C 40/3N) |
|---|---|
| EAN | 9004840390902 |
| Rated current | 40 A |
| Tripping curve | C |
| Poles | 3P+N: 3 protected poles, switched neutral (not protected) |
| Breaking capacity | 4.5 kA (EN 60898-1), 6 kA (EN 60947-2) |
| Rated voltage | 230/400 V AC, 50/60 Hz |
| Width | 4 modules (approx. 70 mm) |
| Terminal capacity | 1 to 25 mm² |
| Power loss | 11.2 W |
| Max. back-up fuse | 80 A gG |
| Degree of protection | IP20, IP40 with cover |
| Ambient temperature | -5 °C to +40 °C (calibrated at 30 °C) |
| Standards | EN 60898-1, EN 60947-2 |
| Reference | 9004840390902 |
| Category | Circuit breakers and RCDs |
| Merk | Schrack |
| Weight | 0.46 kg |
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