Description
Eaton KT3315TA | 3-Pole Thermal-Magnetic Trip Unit
Product Introduction
A replacement trip unit must match the breaker frame and protection requirements of the installed electrical system. A unit with the correct ampere rating but an incompatible frame or trip characteristic is not a valid substitute.
The Cutler-Hammer KT3315TA is listed as a Series C, 3-pole, 315 A interchangeable thermal-magnetic trip unit. Its LI protection functions provide long-time and instantaneous trip protection. Catalog data identifies compatible KW, HKW, and KWC breaker frames and lists a 600 V rating. Verify the exact breaker catalog number and applicable coordination requirements before installation.
For industrial maintenance and surplus procurement, source the KT3315TA by its complete model number and inspect the actual trip unit and mating breaker. Do not assume that a visually similar Series C component has the same rating or frame compatibility.
KT3315TA
Key Technical Specifications
- Manufacturer: Cutler-Hammer / Eaton
- Model: KT3315TA
- Series: Series C
- Trip Unit Type: KT
- Product Type: Interchangeable circuit-breaker trip unit
- Rated Current: 315 A
- Poles: 3
- Protection Technology: Thermal-magnetic
- Trip Functions: LI — Long-Time and Instantaneous
- Listed Voltage: 600 V
- Compatible Frame Families: KW, HKW, KWC
- Application: Circuit-breaker overcurrent protection
- Mounting / Installation: Installs in a compatible breaker frame; confirm the exact breaker and assembly instructions
- Interrupting Rating: Not established by the trip-unit model alone; verify the complete breaker assembly rating
- Adjustability: Confirm available trip settings and adjustment range from the applicable OEM documentation
- Condition: Must be confirmed for the individual unit; listing does not establish tested, refurbished, or unused status
The published catalog description identifies the KT3315TA as a 315 A, 3-pole LI thermal-magnetic trip unit for specified Series C breaker frames. The complete breaker assembly—not the trip unit in isolation—determines system-level suitability and interrupting performance.
Global Sourcing & Inspection SOP
For a used or surplus KT3315TA, inspect the trip unit and verify its compatibility with the existing breaker before approving it as a replacement.
5.1 Inbound Verification
- Photograph the complete nameplate, labels, and molded markings.
- Confirm the exact model .
- Record any serial, date, or revision markings available.
- Inspect the housing for cracks, deformation, heat discoloration, or signs of impact.
- Check terminals and mating interfaces for corrosion, pitting, or mechanical damage.
- Inspect for contamination, moisture exposure, or evidence of unauthorized repair.
- Confirm whether the seller is supplying the trip unit alone or a complete breaker assembly.
- Request written confirmation of condition, test scope, and warranty terms.
5.2 Breaker Compatibility Check
- Record the complete catalog number of the existing breaker.
- Confirm that the breaker frame is an approved match for the .
- Verify the breaker’s voltage and interrupting ratings against the application.
- Confirm that the trip-unit rating and protection functions meet the equipment’s design requirements.
- Check the applicable OEM instructions for installation, retention, and adjustment.
- Do not substitute based only on a matching ampere rating or Series C label.
5.3 Functional Inspection and Testing
- Use qualified electrical personnel and the applicable OEM test procedure.
- Inspect the trip unit and breaker interface before assembly.
- Verify mechanical engagement and retention in the compatible breaker frame.
- Where required, perform approved primary-injection or other trip-function testing with suitable equipment.
- Record test current, trip response, test method, and results.
- Do not use an improvised test setup or bypass protective devices.
- Do not represent the unit as tested unless the test scope and results are documented.
5.4 Final Preparation and Shipment
- Preserve original identification labels and markings.
- Photograph the unit before packing.
- Protect terminals and mating interfaces from impact and contamination.
- Use suitable protective packaging for electrical components.
- Include only the breaker frame, accessories, or documentation explicitly listed in the sales scope.
- Clearly distinguish tested, refurbished, used, and untested surplus condition.
Field Engineer’s Pitfall Guide
❗ Do not confuse the trip unit with a complete circuit breaker
The is an interchangeable trip unit. It does not, by itself, establish the complete breaker’s interrupting rating, enclosure requirements, or suitability for a particular installation.
❗ Verify the breaker frame before installation
The is cataloged for KW, HKW, and KWC frame families. Confirm the exact breaker catalog number and applicable OEM compatibility information before fitting the unit.
❗ Do not assume the 315 A rating establishes the required protection settings
The 315 A designation identifies the trip-unit current rating, but the correct protection selection depends on the circuit, conductor ampacity, load characteristics, and coordination study. Confirm applicable settings and testing requirements before returning the breaker to service.
Intent-Driven FAQ
What is the Cutler-Hammer ?
The is a Series C, 3-pole, 315 A thermal-magnetic interchangeable circuit-breaker trip unit with LI protection functions.
Is the a complete circuit breaker?
No. It is a trip unit intended for installation in a compatible breaker frame. Confirm whether the seller’s offering includes only the trip unit or a complete breaker assembly.
What breaker frames are compatible with the ?
Catalog data identifies KW, HKW, and KWC frame families. Verify the exact breaker catalog number and OEM compatibility before installation.
What does LI protection mean?
LI identifies long-time and instantaneous trip functions. The exact operating characteristics and settings should be verified against the applicable trip-unit and breaker documentation.
What is the current rating of the ?
The is listed at 315 A. This rating should not be treated as a substitute for checking conductor protection, application requirements, and breaker coordination.
Is the obsolete?
The is a legacy Cutler-Hammer Series C component, and surplus or specialist electrical-equipment channels may carry used inventory. Confirm current manufacturer support, availability, and condition directly with the supplier.
What should I verify before buying a used ?
Request clear photos of the model markings, confirm the 315 A rating and compatible breaker frame, inspect the mating interfaces, and obtain the seller’s written condition and test details. For critical service, verify compatibility and perform the required electrical testing before installation.
Bottom Line for Buyers
The Cutler-Hammer is a 315 A, 3-pole Series C thermal-magnetic trip unit with LI protection functions, listed for compatible KW, HKW, and KWC breaker frames.
Before purchasing, verify the complete breaker catalog number, inspect the trip unit’s condition, and confirm that the breaker assembly’s voltage, interrupting rating, and protection requirements are appropriate for the application. A matching trip-unit label alone is not sufficient evidence of a safe replacement.
