Legrand 409071 DX3 10000 A 4-Pole 63 A B-Curve MCB

409071: Legrand DX3 10000 A 4-pole 63 A B-curve MCB, key facts

The Legrand 409071 is a DX3 four-pole miniature circuit breaker rated 63 A with a B release curve. It carries a 10 kA breaking capacity under IEC/EN 60898-1 and 16 kA under IEC 60947-2 at 400 V, which places it between the 6 kA household range and the 25 kA wide-body family. Four poles occupy 70.8 mm of rail. The B curve gives sensitive short-circuit protection for long cables. Seven Star LLC supplies 409071 in Oman and the GCC as an independent supplier in Muscat.

How to read the 409071 description

Technical specifications for 409071

Why a B curve at 63 A with 409071

On long cable runs the loop impedance reduces the fault current at the far end. A C-curve breaker may then fail to reach its magnetic threshold quickly enough, and the cable stays energised under fault. The B curve of 409071 trips between 189 and 315 A for its 63 A rating, so a smaller fault current is enough for fast disconnection. This makes it helpful for long feeders, generator-supplied boards with limited fault current and circuits that need disconnection-time compliance in TN systems.

The trade-off is that B curves are more sensitive to inrush. Transformers, large lighting groups with electronic ballasts and motor starting can trip a B breaker unnecessarily, so use a C or D curve for those loads. The breaker is energy-limiting, class 3, which keeps let-through energy low when a fault does occur.

Where 409071 fits and related parts

This breaker is a common feeder device for sub-boards, kitchens, workshop supplies and small plant rooms at 63 A. Related DX3 references include 407929 (20 A, C, 6 kA family), 409799 (50 A, C, 25 kA family with 1.5-module poles) and the 100 A version 409802. Auxiliary contacts, shunt releases and RCD add-on blocks from the DX3 accessory range can be added, subject to the width and rating limits in the Legrand catalogue.

Selection checklist for 409071

• Load current: 63 A, with the thermal derating for the cabinet temperature considered.
• Cable length: choose B where loop impedance is high and fault current is low.
• Inrush: avoid B on transformers and heavy motor starting; use C or D.
• Fault level: 16 kA Icu at 400 V is the limit; use a higher-rated device above that.
• Conductor: 1.5 to 25 mm² flexible or 1.5 to 35 mm² rigid copper.
• Heat: 63 A in a four-pole row dissipates noticeable heat, so allow spacing or ventilation.

Installation, testing and maintenance of 409071

Mount the breaker on the 35 mm rail and torque the terminals to the recommended 2.5 Nm. Strip conductors 11 mm and check the lugs do not exceed the 14 mm terminal depth. During commissioning verify the loop impedance at the farthest point and confirm that the expected fault current is above the 5 In upper limit of the B band (315 A here) so the magnetic release operates. Record 409071 on the circuit schedule, keep a spare breaker for fast replacement and inspect terminals for discolouration at each annual shutdown.

Typical applications in Oman and the GCC

B-curve 63 A four-pole breakers are used on long outgoing feeders from main boards to remote buildings, pump houses and camp facilities, and on generator-backed boards where fault current is limited. In hot locations a 63 A breaker runs close to the thermal limit inside enclosures, so take the board temperature into account and avoid loading adjacent poles to full rating at once.

Information to send with an RFQ for 409071

• Reference 409071 and the quantity, including spares for panel maintenance.
• Rated current (63 A), curve (B) and number of poles.
• Feeder length, cable size and expected fault current.
• Busbar system and accessories needed.
• 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.

Storage, handling and spares for the Legrand 409071

Keep Legrand 409071 units in their original packaging until they are mounted. Store them indoors in a dry, dust-free room, away from direct sun and condensation. Panel shops in Oman and the GCC often hold stock in warehouses that get very hot in summer, so check that storage temperature stays within the limits given in the manufacturer datasheet.

• Check the label and order code on every unit against the drawing before it goes into the panel.
• Use the correct tool and tightening torque for the terminals, as given in the instructions supplied with the product.
• Keep a small number of spare units for each rating used on site, so that a failed or damaged part can be replaced without waiting for a new shipment.
• Record the order code in the panel documentation and the as-built drawings, so that maintenance teams can reorder the same part later.

When you plan spares for a project, group the Legrand 409071 with the other parts of the same panel in one RFQ. This keeps delivery dates aligned and makes it easier to confirm stock for the whole bill of materials at once.

Documents and quotation

The Legrand technical data sheet that covers 409071 is attached on this page. It gives the range table, dimensions, curves and accessories, so check its notes against your design before you order.

To request a quotation, send reference 409071, 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.