Send a part number, a photo, or a whole BOM — we supply it and stand behind it. Worldwide shipping to 80+ countries.

3G Electric
RFQ CartGet a QuoteSign inSign up
SQUARE D Door Mount Operating Mechanism: Door Mount Op Mechanism, 125 A Amps - Square D Circuit Breaker Handles & Operators
SQUARE DSquare D Circuit Breaker Handles & Operators

SQUARE D Door Mount Operating Mechanism: Door Mount Op Mechanism, 125 A Amps

The SQUARE D Door Mount Operating Mechanism (MPN 9421LB7) is a circuit breaker handle and operator accessory designed for use with NEMA 1, 3, 3R, 4, 4X, and 12 enclosures containing PowerPact(R) B Circuit Breakers…

SKU 3G-OTH-19343

Brand
SQUARE D
Item
Door Mount Operating Mechanism: Door Mount Op Mechanism, 125 A Amps
Category
Square D Circuit Breaker Handles & Operators
Available to Order
Trade pricing by quote — replies within 24h
Qty
WhatsApp an engineer
No account needed — your quote request goes straight to our engineers. A free account lets you track quotes and re-order faster.
Worldwide Shipping
Air & sea freight
Datasheet on Request
Technical specs
1-Day Quote
Replies within 24h

Technical Specifications

SQUARE D
Manufacturer Part Number
9421LB7
Amps
125 A
Poles
3
For Use With
NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers
Accessory Type
Door Mount Operating Mechanism
Number of Poles
3
View Full Spec Sheet

Technical Documents

No technical documents available for this product.
Request documentation →
Not sure this is the right part? Get a recommendation.

Need installation or engineering help?

Installation, commissioning, maintenance plans, system design, and bundled product + service quotes — one team handles the full scope.
Talk to an engineer

Ask a question

SQUARE D Products
3G Electric (S) Pte. Ltd. — Singapore

Product Description

The SQUARE D Door Mount Operating Mechanism (MPN 9421LB7) is a circuit breaker handle and operator accessory designed for use with NEMA 1, 3, 3R, 4, 4X, and 12 enclosures containing PowerPact(R) B Circuit Breakers. This 3-pole, 125 A accessory provides a door-mounted operating mechanism for Square D circuit breakers.

Frequently Asked Questions

What is the Square D 9421LB7 door mount operating mechanism used for?

The Square D 9421LB7 is a door-mounted operating mechanism for PowerPact B circuit breakers. It allows external on/off control of a 3-pole, 125 A breaker housed in NEMA 1, 3, 3R, 4, 4X, or 12 enclosures, enabling safe operation without opening the enclosure door.

What are the specifications of the Square D 9421LB7?

The Square D 9421LB7 is a door mount operating mechanism rated for 125 A and 3 poles. It is designed for use with PowerPact B circuit breakers in NEMA 1, 3, 3R, 4, 4X, and 12 enclosures. The accessory type is a door mount operating mechanism, manufactured by Square D.

Where to buy the Square D 9421LB7 worldwide?

3G Electric supplies the Square D 9421LB7 door mount operating mechanism worldwide. As a global industrial distributor, we handle full logistics, customs clearance, and delivery to your site. Contact us for availability and lead time; we source and deliver this Square D accessory globally.

How to install the Square D 9421LB7 door mount operating mechanism?

Install the Square D 9421LB7 by mounting it on the enclosure door per the manufacturer's instructions. Align the mechanism with the PowerPact B breaker handle, secure with provided hardware, and verify smooth operation. Always disconnect power before installation and follow local electrical codes.

Used in

Common applications for SQUARE D
Commercial building electrical panels — Square D QO series plug-in circuit breakers for branch circuit protection
Industrial motor control centers — Square D QOB series bolt-on breakers in NQOD panelboards
Heating equipment installations — Square D QOU series unit-mount breakers for overcurrent protection
Outdoor electrical distribution — Square D L-Frame enclosures housing LAL/LHL breakers for 400 A service
Indoor facility power distribution — Square D Q-Frame enclosures with QBL/QDL breakers for 225 A circuits
Retrofit and replacement in existing Square D load centers — QO series breakers for 120/240V AC systems

SQUARE D Products

3G Electric supplies SQUARE D square d circuit breaker handles & operators. We supply genuine products with in-stock availability on common SKUs, technical documentation, commissioning support, and warranty service — worldwide.

You might also need

Burners & Combustion →Pumps & Compressors →Spare Parts →All Products →

Similar products

Matched by specification & description
SQUARE D Rotary Operator: Rotary Operator, 125 A Amps, 3 Poles, 3 in Handle/Long Shaft (MPN 9421LB3). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 3; Includes: 3 in Handle; Brand: SQUARE D; Accessory Type: Rotary Operator.
SQUARE D
SQUARE D Rotary Operator: Rotary Operator, 125 A Amps, 3 Poles, 3 in Handle/Long Shaft (MPN 9421LB3). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 3; Includes: 3 in Handle; Brand: SQUARE D; Accessory Type: Rotary Operator.
SQUARE D Rotary Operator: Rotary Operator, 125 A Amps, 3 Poles, 6 in Handle/Std Shaft (MPN 9421LB1). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 3; Includes: Standard Shaft; Brand: SQUARE D; Accessory Type: Rotary Operator.
SQUARE D
SQUARE D Rotary Operator: Rotary Operator, 125 A Amps, 3 Poles, 6 in Handle/Std Shaft (MPN 9421LB1). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 3; Includes: Standard Shaft; Brand: SQUARE D; Accessory Type: Rotary Operator.
SQUARE D Flange Mounted Cable Operating Mechanism with 36" Cable: 125 A Amps, 2 and 3 Poles (MPN 9422CSB30). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 2 and 3; Brand: SQUARE D; Accessory Type: Flange Mounted Cable Operating Mechanism with 36" Cable.
SQUARE D
SQUARE D Flange Mounted Cable Operating Mechanism with 36" Cable: 125 A Amps, 2 and 3 Poles (MPN 9422CSB30). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 2 and 3; Brand: SQUARE D; Accessory Type: Flange Mounted Cable Operating Mechanism with 36" Cable.
SQUARE D Cable Operating Mechanism with 120" Cable: Cable Op Mechanism with 120" Cable, 125 A Amps (MPN 9422CSB10). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 2 and 3; Brand: SQUARE D; Accessory Type: Cable Operating Mechanism with 120" Cable.
SQUARE D
SQUARE D Cable Operating Mechanism with 120" Cable: Cable Op Mechanism with 120" Cable, 125 A Amps (MPN 9422CSB10). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 2 and 3; Brand: SQUARE D; Accessory Type: Cable Operating Mechanism with 120" Cable.
SQUARE D Circuit Breaker Operator: Cb Variable Dp Mechanism, PowerPact(R) J Circuit Breakers (MPN 9422RQ1). Key specifications — For Use With: PowerPact(R) J Circuit Breakers; Number of Poles: 3; Brand: SQUARE D; Accessory Type: Cb Variable Depth Mechanism.
SQUARE D
SQUARE D Circuit Breaker Operator: Cb Variable Dp Mechanism, PowerPact(R) J Circuit Breakers (MPN 9422RQ1). Key specifications — For Use With: PowerPact(R) J Circuit Breakers; Number of Poles: 3; Brand: SQUARE D; Accessory Type: Cb Variable Depth Mechanism.
SQUARE D Cable Operating Mechanism with 60" Cable: Cable Op Mechanism with 60" Cable, 125 A Amps (MPN 9422CSB50). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 2 and 3; Brand: SQUARE D; Accessory Type: Cable Operating Mechanism with 60" Cable.
SQUARE D
SQUARE D Cable Operating Mechanism with 60" Cable: Cable Op Mechanism with 60" Cable, 125 A Amps (MPN 9422CSB50). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 2 and 3; Brand: SQUARE D; Accessory Type: Cable Operating Mechanism with 60" Cable.

More from SQUARE D

View all SQUARE D parts →
SQUARE D Handle Assembly: Handle Assembly, Type MEL, MXL, MAL, and MHL Circuit Breakers, 2/3 Poles (MPN 9421LT4). Key specifications — For Use With: Type MEL, MXL, MAL, and MHL Circuit Breakers; Number of Poles: 2; Includes: 8 in Long Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.
SQUARE D
SQUARE D Handle Assembly: Handle Assembly, Type MEL, MXL, MAL, and MHL Circuit Breakers, 2/3 Poles (MPN 9421LT4). Key specifications — For Use With: Type MEL, MXL, MAL, and MHL Circuit Breakers; Number of Poles: 2; Includes: 8 in Long Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.
SQUARE D Rotary Operator: Rotary Operator, 125 A Amps, 3 Poles, 6 in Handle/Long Shaft (MPN 9421LB4). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 3; Includes: Long Shaft; Brand: SQUARE D; Accessory Type: Rotary Operator.
SQUARE D
SQUARE D Rotary Operator: Rotary Operator, 125 A Amps, 3 Poles, 6 in Handle/Long Shaft (MPN 9421LB4). Key specifications — For Use With: NEMA 1, 3, 3R, 4, 4X, 12 Enclosures with PowerPact(R) B Circuit Breakers; Number of Poles: 3; Includes: Long Shaft; Brand: SQUARE D; Accessory Type: Rotary Operator.
SQUARE D Variable Depth Operating Mechanism: Variable Dp Op Mechanism, 125 A Amps (MPN 9422RB1). Key specifications — For Use With: Custom Built Control Enclosures with PowerPact(R) B Circuit Breaker; Number of Poles: None; Brand: SQUARE D; Accessory Type: Variable Depth Operating Mechanism.
SQUARE D
SQUARE D Variable Depth Operating Mechanism: Variable Dp Op Mechanism, 125 A Amps (MPN 9422RB1). Key specifications — For Use With: Custom Built Control Enclosures with PowerPact(R) B Circuit Breaker; Number of Poles: None; Brand: SQUARE D; Accessory Type: Variable Depth Operating Mechanism.
SQUARE D Handle Assembly: Handle Assembly, 2/3 Poles, 6 in Chrome-Plated Handle (MPN 9421LC46). Key specifications — For Use With: PowerPact(R) B, H, J, D, and L Circuit Breakers; Number of Poles: 3; Includes: 6 in Chrome-Plated Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.
SQUARE D
SQUARE D Handle Assembly: Handle Assembly, 2/3 Poles, 6 in Chrome-Plated Handle (MPN 9421LC46). Key specifications — For Use With: PowerPact(R) B, H, J, D, and L Circuit Breakers; Number of Poles: 3; Includes: 6 in Chrome-Plated Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.
SQUARE D Rotary Operating Handle: Rotary Op Handle, PowerPact(R) H and J Circuit Breakers (MPN S29343). Key specifications — For Use With: PowerPact(R) H and J Circuit Breakers; Number of Poles: None; Includes: Telescoping Shaft and Operator; Brand: SQUARE D; Accessory Type: Rotary Operating Handle.
SQUARE D
SQUARE D Rotary Operating Handle: Rotary Op Handle, PowerPact(R) H and J Circuit Breakers (MPN S29343). Key specifications — For Use With: PowerPact(R) H and J Circuit Breakers; Number of Poles: None; Includes: Telescoping Shaft and Operator; Brand: SQUARE D; Accessory Type: Rotary Operating Handle.
SQUARE D Open Door Shaft Operator: Open Door Shaft Operator, PowerPact(R) B Circuit Breakers (MPN LV426937). Key specifications — For Use With: PowerPact(R) B Circuit Breakers; Number of Poles: None; Brand: SQUARE D; Accessory Type: Open Door Shaft Operator.
SQUARE D
SQUARE D Open Door Shaft Operator: Open Door Shaft Operator, PowerPact(R) B Circuit Breakers (MPN LV426937). Key specifications — For Use With: PowerPact(R) B Circuit Breakers; Number of Poles: None; Brand: SQUARE D; Accessory Type: Open Door Shaft Operator.
SQUARE D Handle Assembly: Handle Assembly, Type KAL, KCL, and KHL Circuit Breakers, 2/3 Poles (MPN 9421LP1). Key specifications — For Use With: Type KAL, KCL, and KHL Circuit Breakers; Number of Poles: 3; Includes: 6 in Long Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.
SQUARE D
SQUARE D Handle Assembly: Handle Assembly, Type KAL, KCL, and KHL Circuit Breakers, 2/3 Poles (MPN 9421LP1). Key specifications — For Use With: Type KAL, KCL, and KHL Circuit Breakers; Number of Poles: 3; Includes: 6 in Long Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.
SQUARE D Handle Assembly: Handle Assembly, 2/3 Poles, 6 in Long Handle (MPN 9421LJ1). Key specifications — For Use With: Compact NSF Circuit Breakers; Number of Poles: 2; Includes: 6 in Long Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.
SQUARE D
SQUARE D Handle Assembly: Handle Assembly, 2/3 Poles, 6 in Long Handle (MPN 9421LJ1). Key specifications — For Use With: Compact NSF Circuit Breakers; Number of Poles: 2; Includes: 6 in Long Handle; Brand: SQUARE D; Accessory Type: Handle Assembly.