Eaton Series C Circuit Breakers for Switchboards

Eaton/Cutler-Hammer Series C breakers protect industrial switchboards using molded-case circuit breaker technology

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When you’re designing or upgrading electrical switchboards, Eaton / Cutler-Hammer Series C molded-case circuit breakers give you dependable performance across industrial applications. You’ll find these breakers industrial switchboards because they’re tested for reliability and consistent coordination across every frame size.

Why Series C Family Matters for Industrial Switchboards

If you’re upgrading, replacing or installing switchboards in a facility, or for switchboard temporary power, it’s critical to protect feeders and branch circuits. Eaton Series C breaker lineup in the Series C family lets you maintain UL 489 compliance with flexibility, modular accessories, and predictable time-current performance.

This means you can standardize designs and streamline maintenance across your entire facility.

Switchboard Breaker Frame-by-Frame Breakdown: FD, KD, LD, MD, ND, PD

Each Series C breaker is defined by its frame size and interrupting capacity:

FD-Frame: Up to 250 A – ideal for branch and lighting panels.
KD-Frame: 70 A to 400 A – a solid choice for medium-sized feeders and HVAC loads.
LD-Frame: 125 A to 600 A – used in mid-range industrial feeders.
MD-Frame: 200 A to 800 A – popular in heavy-duty distribution applications.
ND-Frame: 300 A to 1,200 A – a workhorse for switchboard molded case breaker installations.
PD-Frame: 400 A to 1,600 A – the largest Series C frame for high-capacity feeders and main breakers.

By choosing the right switchboard breaker frame size, you can balance protection, coordination, and footprint.

Key Features and Differences Across Frame Sizes

No matter which Series C breaker you pick, there’s standardized accessories, consistent terminal designs, and configurable trip units. The higher frames—ND and PD—offer interrupting ratings and advanced trip technologies, making them good for switchboards feeding multiple downstream loads. Also, smaller frames like FD and KD provide compact protection with the same reliability.

How to Select the Right Frame for Your Switchboard Application

When selecting a breaker for switchboards, start by evaluating the load current, voltage rating, and fault current available at the point of installation. Eaton Series C sizing charts and coordination tables make it easy to match frame and trip units to your switchboard project.

By standardizing on the Eaton Series C breaker platform, you’ll simplify parts selection, training, and maintenance across multiple switchboards.

Retrofit and Compatibility Considerations for Switchboards

If you maintain legacy Cutler-Hammer gear or current model Eaton molded case breakers, you’ll like the molded-case breaker retrofit options built into the Series C family. You can drop in new breakers without redrilling mounting patterns or rewiring lugs. This reduces downtime and keeps your switchboard up to current UL standards while using modern trip technology.

Eaton Series C breaker line supports shunt trips, auxiliary switches, bell alarms, and arc-flash reduction accessories. For coordinated protection, molded case breaker switchboard solutions can be paired with upstream and downstream devices for selective coordination that minimizes outages and protects equipment.

In Data centers and manufacturing, Series C breakers can use the smaller frames in lighting panels and the larger frames in main distribution sections. They also integrate nicely with motor control centers where feeder and branch protection need to work together.

Best Practices and Maintenance Tips for Series C Breakers

Perform routine visual inspections and trip tests to verify contact wear and trip mechanisms are working. Keep mounting hardware tight and replace any accessories that show signs of age. Following Eaton’s maintenance guidelines means your molded case breaker switchboard assemblies stay safe and reliable for years.

What You Should Know

What makes the Eaton Series C breaker ideal for industrial switchboards?

Eaton Series C breakers are designed for high-performance switchboard applications that require dependable protection, compact form factors, and consistent coordination across multiple feeders. They meet UL 489 standards and offer frame sizes (FD through PD) that fit both branch and main breaker compartments in industrial switchboards.

Which Series C breaker frame sizes are most common in switchboards?

Most industrial switchboards use ND and PD frame molded-case breakers for main and feeder sections because of their higher ampere ratings (up to 1600 A) and strong interrupting capacities. Smaller FD and KD frames are often used for lighting or branch sections within the same lineup.

Can Eaton Series C breakers be used to retrofit older Cutler-Hammer or Westinghouse switchboards?

Yes. The Eaton Series C molded-case circuit breaker line is backward-compatible with legacy Cutler-Hammer and many Westinghouse switchboards. These breakers share common footprints and mounting hole patterns, allowing for direct retrofit without major panel modifications.

What standards apply to switchboards using Series C breakers?

Switchboards equipped with Eaton Series C breakers are typically built to UL 891 (switchboards) and UL 489 (circuit breakers) standards. These certifications mean safety, selective coordination, and consistent performance for low-voltage power distribution systems.

What accessories are available for Series C breakers in switchboards?

You can enhance your Series C breaker switchboard with shunt trips, auxiliary switches, bell alarms, and arc-flash reduction modules. These accessories improve operational visibility and maintenance safety, especially in large switchboard assemblies.

How do I select the right Series C breaker for my switchboard application?

Choose your molded-case breaker based on system voltage, load current, and fault current available at the bus. Eaton’s Series C frame size guide and coordination tables help you match FD through PD frames to each switchboard compartment, ensuring proper protection and selective coordination.

What maintenance is recommended for Series C breakers in switchboards?

Perform regular visual inspections, contact resistance tests, and functional trip testing. Keeping breaker terminals tight, cleaning dust buildup, and checking mechanical operation will help your Eaton Series C switchboard breakers maintain reliability and extend service life.

If you’re building new switchboards or upgrading existing gear, the Eaton Series C breaker family gives you flexibility, compatibility, and performance for current industrial demands. If you need help sourcing FD through PD frames or planning a molded-case breaker retrofit, reach out to Relectric for support: 800.497.6255.

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