Legrand 409802 DX3 4-Pole 100 A C-Curve MCB

409802: Legrand DX3 4-pole 100 A C-curve MCB, what the reference means

The Legrand 409802 is a four-pole modular thermal-magnetic miniature circuit breaker from the DX3 range, rated 100 A with a C release curve. The catalogue describes it as a device for control, protection and isolation of electrical circuits with fully visible breaking, a 25 kA breaking capacity at 400 V AC and finger-safe IP20 terminals. All four poles are protected and the neutral pole switches together with the phases. Seven Star LLC supplies 409802 in Oman and the GCC as an independent supplier in Muscat.

At 100 A this breaker sits at the top of the modular range. It is wider than the small DX3 ratings, taking six modular spacings (106.8 mm) for four poles, and it is intended for incomers and large sub-distribution feeders rather than for final circuits. The catalogue page lists no attached technical sheet for this exact rating, so the figures below come from the product page itself.

Reading the description of 409802

Technical specifications for 409802

How the 409802 protects a feeder

Two release mechanisms work inside the breaker. A thermal element, a bimetal strip heated by the load current, opens the circuit slowly when a current above 100 A persists, which protects the cable from overheating. A magnetic element reacts within milliseconds to a short circuit and drives the contacts open before the fault energy can damage the board. The C characteristic places the magnetic trip band above the inrush of transformers, lighting groups and small motor starters, so it is a sensible default for mixed three-phase feeders.

The four poles open together, so a trip or a manual operation isolates the neutral as well. The catalogue highlights fully visible breaking, which means the handle position reflects the true contact position; this is useful for lock-out and maintenance routines where an electrician must be sure that the feeder is dead before work starts.

Where 409802 fits in a board and related DX3 parts

Use 409802 as the incoming breaker of a sub-board, as the feeder for a motor control section or as the protection of a busbar trunking tap-off. For smaller feeders the same range offers sibling breakers such as 409799 (50 A, C curve) in the same 4-pole 25 kA family; for compact 1-module-per-pole versions, see references such as 407929 and 409071. Residual current protection can be added with Legrand RCD add-on blocks, subject to compatibility of the breaker width and rating, which should be checked against the catalogue before ordering. Where the prospective short-circuit current exceeds 25 kA at 400 V, a moulded-case breaker from the DPX3 range is the correct step up.

Selection checklist for 409802

• Load current: 100 A continuous is the upper limit; derate for high ambient temperature inside closed cabinets.
• Prospective short-circuit current at the board: must not exceed 25 kA at 400 V (50 kA at 230 V).
• Conductor size: terminals accept 6 to 50 mm² multi-wire or 6 to 70 mm² solid-core copper.
• Curve: C suits mixed loads; confirm that downstream devices and cable lengths still give reliable tripping.
• Space: six modular spacings, depth 79.2 mm, so check the door clearance and busbar system.
• Pollution degree 3 and IP20 terminals require a clean, enclosed board with the cover in place.

Installation, commissioning and maintenance of 409802

Snap the breaker on a 35 mm DIN rail, connect the supply from top or bottom, and tighten the terminal screws to the torque given in the instruction sheet that accompanies the device. Use cable lugs or conductors within the stated cross-section range, and check each termination for heat marks during the first thermographic survey after load is applied. After commissioning, record the breaker reference 409802 on the circuit schedule and fit the label in the holder. Operate the handle at each planned shutdown to keep the mechanism free, and replace a breaker that has cleared a high-energy fault rather than re-using it.

Typical applications in Oman and the GCC

Large modular breakers like this are used in commercial buildings, camps, workshops, water pumping stations and utility rooms across Oman and the GCC, where a 100 A four-pole incomer feeds a sub-board. In hot sites the cabinet temperature often rises well above the room temperature, and dust is common, so keep ventilation clear, close unused cut-outs and size the breaker with the thermal margin in mind. The operating range of -25 to 70 °C covers most indoor panel conditions.

Family and sibling ratings next to 409802

Information to send with an RFQ for 409802

• Reference 409802 and the quantity, including spares for panel maintenance.
• Rated current (100 A) and curve (C), and whether a B or D curve is needed instead.
• Prospective short-circuit current at the board and the supply voltage.
• Conductor type and cross-section to be connected.
• Delivery location (Muscat, Sohar, Salalah or elsewhere in the GCC) and the date you need the goods.
• Any documents you need with the quotation, such as a technical data sheet or a compliance statement.

Documents and quotation

Send us the reference 409802 and we will confirm which documents are available for this item before you order. Compare the ratings with the installation design before you place an order.

To request a quotation, send reference 409802, the quantity and your delivery location. Seven Star LLC is an independent supplier in Muscat and is not affiliated with the manufacturer; we will confirm availability and lead time for your order.