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Square D QOB240 bolt-on circuit breaker, two-pole paddle actuator, grey plastic housing

SQUARE D

SQUARE D QOB240 Circuit Breaker 40A 2 Pole 120/240V AC

SKU CH-6PM9-BBNMH

Bolt-on 2-pole breaker rated 40 A at 120/240 V AC with 10 kA interrupting for QO load centres

  • 40 A two-pole protection for 120/240 V AC circuits
  • 10 kA interrupting rating handles high fault currents
  • Bolt-on mounting fits Square D QO and NQOD panelboards
  • Lug terminals accept wire directly for secure connections
  • Compact 3.1 in length saves panel space

QO Series Bolt-On 40 A Breaker

The SQUARE D QOB240 is a 40 A, two-pole miniature circuit breaker rated for 120/240 V AC and 48 V DC. It mounts by bolt-on into compatible QO series panelboards and load centres, with a standard paddle actuator and lug terminals. The frame size is 100 A and the interrupting rating is 10 kA at 120/240 V AC. Physical dimensions are 3.1 in long, 1.5 in wide and 2.9 in deep.

Installers and panel builders

Electricians wiring or upgrading QO or NQOD panelboards will find this breaker fits the designated mounting style and voltage requirements. It is not suited for panels that accept only plug-on breakers, for applications requiring a higher interrupting rating, or for DC systems exceeding 48 V. Buyers needing a different ampere rating, a single-pole device, or a non-bolt-on mounting method should look elsewhere.

10 kA interrupting rating at 120/240 V AC

The maximum AIR rating of 10 kA determines whether this breaker can safely clear a fault on the intended circuit. Verify that the available short-circuit current at the installation point does not exceed this value before specifying the QOB240.

How it compares

Measured against everything we stock in Breakers & Circuit Protection, at today’s prices. Recalculated every night.

Price $59.99
Typical for this category: the median of 1,135 items is $54.99.

Specifications

Product
Brand nameSQUARE D

Questions about this item

Will the 3.1 in length and 1.5 in width fit my Square D QO load center?

The breaker measures 3.1 in long, 1.5 in wide and 2.9 in deep, matching the standard QO frame size for bolt-on mounting.

How do I bolt the QOB240 onto the bus bar, and what step is often missed?

Align the bolt-on terminals with the panel's bus stabs, torque the mounting screws to spec, then snap the paddle actuator closed to engage the breaker.

When should I replace this 40 A two-pole breaker?

Replace it if the paddle trips repeatedly under normal 40 A load, shows discoloration at the lug terminals, or fails to reset after a verified overcurrent event.

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