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Eaton / Westinghouse MA3400 Molded Case Circuit Breaker
- 400A
- 3 Pole
- Bolt-On
Eaton / Westinghouse
MA3400
Molded Case Circuit Breaker
Brand
Eaton / Westinghouse
SKU
MA3400
Quantity
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Eaton / Westinghouse MA3400 - 400A 3 Pole Molded Case Circuit Breaker
Re-Certified
Quantity
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Description
Maintaining older electrical systems requires exact-fit components, and this 400A molded case circuit breaker delivers precisely that for commercial facilities. It acts as a direct substitute for discontinued Westinghouse and Cutler-Hammer M-Frame devices, fitting perfectly into existing switchboards and motor control centers. Equipped with an interchangeable thermal-magnetic trip unit, it handles up to 600VAC while providing a solid 30kAIC interrupting capacity at 480VAC for reliable safety.Specifications
| Brand | Eaton / Westinghouse |
|---|---|
| Part Number | MA3400 |
| Series | MA |
| Amperage | 400A |
| Poles | 3 |
| Mounting Style | Bolt-On |
| Voltage | 600VAC, 250VDC |
| Phase | 3 |
| AIC Rating | 42kA @ 240VAC, 30kA @ 480VAC, 22kA @ 600VAC, 10kA @ 250VDC |
| Frame Type | MA |
|---|---|
| Terminal Type | Lugs |
| For Use With | Westinghouse Panelboards, Switchboards, Motor Control Centers, Eaton Series C Panelboards |
| Wire Gauge | (2) 1 AWG - 500 kcmil (Al/Cu) |
| Max Wire | 500 kcmil |
| Min Wire | 1 AWG |
| Trip Technology | Thermal Magnetic |
|---|---|
| Trip Function Code | LI |
| Trip Function | Long-Time, Instantaneous |
| Trip Adjustability | Fixed Thermal, Adjustable Magnetic |
| Available Options | Shunt Trip, Auxiliary Switch, Undervoltage Release, Alarm Switch |
|---|---|
| Accessories | Lugs |
| Standards | CSA C22.2 No. 5, NEMA AB-1, UL 489 |
| Approval | CSA, UL |
| Temp Rating | 40C |
| Construction Features | Interchangeable Trip Unit |
Product FAQs
8 answersWhat equipment is the MA3400 compatible with?
It is designed for use in vintage Westinghouse panelboards, switchboards, and motor control centers, as well as Eaton Series C panelboards. It serves as an exact drop-in replacement for aging M-Frame breakers.
Is the Westinghouse MA3400 the same as the Eaton MA3400?
Yes. Eaton acquired the Westinghouse distribution equipment division. Breakers labeled Eaton, Cutler-Hammer, or Westinghouse with the MA3400 catalog number are the exact same M-Frame device.
What is the modern replacement for the obsolete MA3400?
The MA3400 is a legacy M-Frame breaker. Eaton's direct modern replacement is the MDL3400, which is an MDL-Frame breaker. Note that replacing an MA frame with an MDL frame may require different mounting hardware or retrofit kits depending on your specific panelboard.
What does the LI trip function code mean on the MA3400?
LI stands for Long-Time and Instantaneous trip functions. The thermal element provides fixed long-time protection against overloads, while the magnetic element offers adjustable instantaneous protection against short circuits.
Can the MA3400 be used in direct current applications?
Yes, the MA3400 is rated for up to 250VDC with an interrupting capacity of 10kAIC. This makes it suitable for specific DC systems, in addition to its standard 600VAC rating.
Does the MA3400 require a retrofit kit to install in an older Westinghouse panel?
No. Because the MA3400 is an exact M-Frame drop-in replacement, it installs directly into vintage Westinghouse panelboards, such as the PRL4, without the need for retrofit kits.
What are the wire size requirements for the MA3400 lugs?
The standard lugs on the MA3400 feature a dual-barrel design to support parallel feeds. They accept two conductors per phase, ranging from 1 AWG to 500 kcmil for either aluminum or copper wire.
What safety precautions should be taken before installing the MA3400?
Ensure all power to the panelboard or switchboard is completely de-energized and verified with a voltage meter. Only licensed electricians should perform the installation, and all lug torque specifications must be strictly followed to prevent arcing or thermal failure.
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Reviews
Review summary
Customers rate this product 5.0 out of 5 based on 1 review.
Total 5 star reviews: 1 Total 4 star reviews: 0 Total 3 star reviews: 0 Total 2 star reviews: 0 Total 1 star reviews: 0
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1 review
- DHDave H.ReviewingSquare D MA36600 - 600A 3 Pole Molded Case Circuit BreakerI recommend this productRated 5 out of 5 stars6/6/25Never had a problem
We like the service and the prices. The re-certified are great for projects that we have in house.