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Square D NQB550 - 50A 2-Pole Miniature Circuit Breaker (10kA AIC)

Square D
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Square D NQB550 is a 50-amp, 2-pole, 120/240-volt AC miniature circuit breaker designed for overload and short-circuit protection in residential and commercial load centers. It provides a 10,000 AIC interrupting rating at 120/240VAC and features a thermal-magnetic trip mechanism for reliable overcurrent response. The breaker is constructed with a compact 1-inch per pole design, a plug-on mounting style, and copper alloy line and load terminals for secure connections. It complies with UL 489 and CSA C22.2 No. 5 standards, ensuring safe operation in North American electrical systems. This unit is commonly used in Square D QO load centers for branch circuit protection in lighting, appliance, and general-purpose power distribution applications.

Key Features & Specifications
  • Type: Miniature Circuit Breaker, Thermal-Magnetic, Plug-On
  • Voltage Rating: 120/240 VAC
  • Current Rating: 50 A
  • Dimensions: 3 in (76.2 mm) Height x 1 in (25.4 mm) Width x 2.75 in (69.85 mm) Depth (per pole)
  • Standards: UL 489, CSA C22.2 No. 5
  • Applications: Branch circuit protection in QO load centers
  • Switch Type: Toggle
  • Configuration: 2-Pole
  • Coil Voltage Maximum: Not applicable (thermal-magnetic)
  • Temp Rating: 40°C ambient
  • Shipping Dimensions: 50 in (1270 mm) x 14 in (355.6 mm) x 5.75 in (146.05 mm) (Height x Width x Depth)
  • Phase: 1-Phase
  • Voltage: 120/240 VAC
  • Amperage: 50 A
  • AIC rating: 10 kA at 120/240 VAC
  • Connection: Plug-On
  • Poles: 2
  • Protection: Overload and Short-Circuit
  • Functions: Overcurrent Protection
  • Frame Size: QO
  • Trip Type: Thermal-Magnetic
  • Panel Type: QO Load Center
  • Breaker Type: Miniature Circuit Breaker
  • Control Voltage Minimum: Not applicable
  • Control Voltage Maximum: Not applicable
  • MCM Size: Not applicable
  • Metal Type: Copper alloy terminals
  • Panel Style: QO
  • Bus Type: Plug-on bus
  • Fuse Class: Not applicable
  • Insulation Temperature: 75°C
  • Inductance: Not specified
  • Impedance: Not specified
  • Barrels: Not applicable
  • Class Rating: Not applicable
  • Diameter: Not applicable
  • Velocity: Not applicable
  • Clip Center: Not applicable
  • Clas: Not applicable
  • Mounting: Plug-On
  • Hz: 50/60 Hz
  • Coil Material: Not applicable
  • Horse Power: Not specified
  • Aux Contacts: Not included
  • CPT: Not included
  • Full Load Amps: 50 A
  • Dist Voltage: Not applicable
  • Bucket Size: Not applicable
  • Bucket Style: Not applicable
  • Bucket Type: Not applicable
  • Full Load Amp Maximum: 50 A
  • Full Load Amp Minimum: 50 A
  • Enclosure: Open (without enclosure)
  • Relay Style: Not applicable
  • Coil Voltage Minimum: Not applicable
  • Wire: Copper or aluminum
  • Amperage Maximum: 50 A
  • Amperage Minimum: 50 A
  • Nema Rating: Not applicable
  • Switch Style: Toggle
  • Wire Size: 14 AWG to 6 AWG
  • Certification: UL Listed, CSA Certified
  • Circuit Breaker Mounting Style: Plug-On
  • Terminal Connection: Line and Load
  • Frequency Rating: 50/60 Hz
  • Phase Connection: Single-Phase
  • Standards: UL 489, CSA C22.2 No. 5
  • Compatible Frames: QO
  • Installation Type: Plug-On
  • Item QTY: 1
  • Nema Starter Size: Not applicable
  • Breaker Frame: QO
  • Current Rating: 50 A
  • Reverse Standoff Voltage: Not applicable
  • Watts: Not applicable
  • Peak Pulse Current: Not applicable
  • Breakdown Voltage (MIN VBR@IT ) (V): Not applicable
  • Breakdown Voltage (VBR@IT) (V): Not applicable
  • Polarity: Not applicable
  • Operating Temperature Maximum Celsius: 40°C
  • Max Clamp Voltage: Not applicable
  • On-State Current: Not applicable


Product Identification
  • UPC: 78590104910
  • GTIN: 00785901049104