A9N18377

What is this device used for?

It is a miniature circuit-breaker designed to protect electrical distribution circuits against overloads and short circuits using a thermal-magnetic trip mechanism.

How many poles does it have, and what does that mean in practice?

It is a 4-pole (4P) breaker with four protected poles, typically used to switch and protect three-phase circuits with a neutral or other four-conductor arrangements.

What is the rated current?

The rated current is 125 A (at 30 °C).

What does a C tripping curve mean?

A C curve breaker trips magnetically at approximately 5 to 10 times its rated current, making it suitable for many general distribution circuits where moderate inrush currents may occur.

What is the breaking capacity?

It has 10,000 A (10 kA) rated short-circuit breaking capacity (Icn) at 230–400 V AC to EN/IEC 60898-1, and rated ultimate short-circuit breaking capacities (Icu) up to 20 kA depending on the operating voltage to EN/IEC 60947-2.

Which voltages can it be used on?

Typical rated operational voltages include 230–400 V AC, 380–415 V AC, 440 V AC (50/60 Hz), and up to 500 V DC (as specified for the device).

Is it suitable for AC networks only?

It is specified for AC networks and also lists a DC operational rating up to 500 V DC for appropriate applications, so it may be used on DC circuits where the stated rating applies.

Can it be used as an isolator?

Yes. It is stated as suitable for isolation in accordance with IEC 60947-2.

How is it mounted in a panel?

It is a clip-on device designed for mounting on a 35 mm symmetrical DIN rail.

What are the physical dimensions and weight?

Approximate dimensions are 81 mm (height) x 108 mm (width) x 73 mm (depth), with a product weight of about 0.82 kg.

What does '12 x 9 mm pitches' refer to?

It indicates the overall module width on the DIN rail system: 12 pitches at 9 mm each, which corresponds to 108 mm total width.

What cable sizes can the terminals accept?

Tunnel terminals accept 1–50 mm² rigid conductors and 1.5–35 mm² flexible conductors, with a recommended wire stripping length of 15 mm.

What tightening torque is recommended for the terminals?

The specified tightening torque is 3.5 N·m.

Is it compatible with comb busbars?

Yes, it is specified as compatible with comb busbars and distribution blocks.

Does it include earth-leakage (RCD) protection?

No. Earth-leakage protection is via a separate block; this unit is an overcurrent protective device (MCB) and does not provide residual current protection on its own (A9N18377).

Does it provide a clear ON/OFF status indication?

Yes. It has local ON/OFF indication and a contact position indicator.

What are the environmental and enclosure ratings?

It is rated IP20 and is specified for operation from -25 °C to +70 °C (storage -40 °C to +85 °C), with pollution degree 3 and overvoltage category IV.

What is the expected mechanical and electrical endurance?

Mechanical durability is specified at 20,000 cycles, and electrical durability at 5,000 cycles (to IEC 60947-2).