Siemens 5SY66166 MCB 3P+N B16 16A 6kA 230/400V AC

The Siemens 5SY66166 is a 3-pole + neutral miniature circuit breaker (MCB) with B tripping characteristic, rated for 16 A and 6 kA breaking capacity. Unlike many 4-pole MCBs that use a solid neutral, this unit features a switched neutral pole, providing full isolation of all conductors when tripped. Its compact 4-module width (72 mm) and DIN rail mounting make it ideal for distribution boards where space is limited.

Highlights

• 3P+N configuration with switched neutral for complete isolation
• B curve: trips between 3 and 5 times rated current, suited for resistive and lighting loads
• 6 kA rated switching capacity at 400 V AC
• Energy limiting class 3 for excellent current limitation
• Wide terminal range: 0.75 to 35 mm² (solid) / 0.75 to 25 mm² (stranded)
• Mechanical and electrical service life of 10,000 cycles

In daily use

Installation is straightforward on standard 35 mm DIN rails (EN 60715). The screw terminals accept both solid and stranded conductors, allowing flexible wiring. The breaker's IP20 rating (terminals) ensures finger-safe operation, and with an optional cover, protection increases to IP40. Operating temperature range from -25 °C to +45 °C covers most indoor and sheltered outdoor applications.

Full specifications

• Number of poles: 3P+N (4-pole)
• Tripping characteristic: B
• Rated current: 16 A
• Rated switching capacity: 6 kA at 400 V AC
• Rated voltage: 230/400 V AC
• Frequency: 50/60 Hz
• Degree of protection: IP20 (terminals), IP40 (with cover)
• Energy limiting class: 3
• Overvoltage category: III
• Pollution degree: 3
• Terminal type: Screw terminals
• Terminal capacity (solid): 0.75 to 35 mm²
• Terminal capacity (stranded): 0.75 to 25 mm²
• Mechanical service life: 10,000 switching cycles
• Electrical service life: 10,000 switching cycles
• Ambient operating temperature: -25 to +45 °C
• Product width: 4 modules (72 mm)
• Standard: IEC 60898-1

Final note

The 5SY66166 combines reliable protection with a switched neutral pole, making it a versatile choice for three-phase circuits requiring full isolation.