Eaton DSL Breaker Maintenance & Operation


Eaton DSL Breakers, Current Limiter Fuse
Mounting, Operation & Maintenance

Power fuses and circuit breakers protect equipment during overloads and short
circuits by interrupting electrical flow. Eaton and other manufacturers offer coordinated combinations of breakers and current limiters (fuses) primarily to extend the interrupting rating of circuit breakers up to 200,000 amperes RMS symmetrical current. Class L Current limiters add a level of protection, clearing infrequent high faults before the fault reaches the circuit breaker. This prevents equipment damage or a fire hazard.

“Breakers & Fuses: Like Peanut Butter & Jelly”

In this article we’ll review the description, operation and maintenance of the integrated relationship between Eaton Low Voltage Power breakers and the EATON Class L Current Limiters required. Since their introduction in 1967, Eaton Low Voltage Power DS and DSL breakers, and its predecessor DB and DBL breakers (1950), can be commonly found in an installed base exceeding hundreds of thousands in switchgear applications today.

Let’s take a closer look at some power distribution basics, then move on to Eaton’s fusing and breaker power distribution solution.

Eaton DBL and DSL Racking and Mounting Basics

Eaton DBL and DSL breakers are “draw-out” circuit breakers. Draw out (DO) refers to how the breaker is drawn out – like a drawer — from the breaker cabinet for maintenance. It’s very common for circuit breakers to be racked and mounted horizontally like drawers in a cabinet, often called an enclosure. The highest amp rated DBL and DSL Current Limiter fuses are mounted in the breaker cabinet using “trucks” (explained later) for easy access and fuse replacement.

Eaton Low Voltage Fusing for Eaton DSL Breakers

DBL and DSL circuit breakers are a coordinated combination of breakers and current limiting power fuses.  System coordination between the breaker and power fuse prevents equipment damage and fire hazards caused by extremely high fault currents upstream and downstream from the power source.

Eaton Current Limiting Class L fuses provide a protective upper limit (interrupting rating) on the current. In other words, these current limiting fuses protect the circuit breaker on faults above the fault protection rating of the breaker.

Reducing the Potential for Arc Flash

In a recent article in Electrical Construction and Maintenance Bob Fuhr, P.E.,, had this to say about reducing arc flash:

“Design engineers have a few options to reduce system voltage or fault currents. However, the best and most direct way to reduce arc flash hazards is to reduce fault-clearing times. You can reduce the incident energy level by replacing older non-current limiting fuses with modern fast operating fuses with faster clearing times. Even replacing expulsion-type fuses with current-limiting fuses have been shown to be beneficial”.

“Another simple method is to reduce the fuse ampere size. Many circuits in a distribution system are under-utilized. If a 400A fuse is feeding loads that draw only 200A, then the 400A fuse can be reduced, which will increase the chances that the fuse will operate in the current-limiting region for an arcing fault. However, it’s important to check the inrush current of motors and transformers and verify that the fuse will not be damaged when these devices are energized”.

What’s a DSL Breaker Fuse Truck?

Fuse truck mountings allows separate mounting and isolation for Class L fuses because of the fuse’s sizing and high temperature characteristics. These draw-out trucks physically fit in the same compartments as DS and DSL model circuit breakers. They are moved in and out of the cabinet compartment using a levering mechanism similar to the breaker levering mechanism. The fuse truck is normally installed with a circuit breaker of the same current rating.

The current limiting fuses can only be removed from the circuit breaker and replaced when the circuit breaker is removed from the enclosure. DSL breaker cabinet enclosures include visual indicators like the Blown Limiter Indicator indicating a current limiter (fuse) has interrupted a short circuit, causing the breaker to trip. Eaton NCL fuses are normally provided when the fuse truck is built unless otherwise specified. However, any Class L current limiting fuse of the proper current rating, design and physical configuration can be used as a replacement.

Eaton DSL Breaker and Fuse Truck Highlights

  • Class L Fuses extend interrupting rating up to 200,000 amperes
  • Available in four frame sizes, DSL-206, DSL-416, DSL-632, DSL-840
  • Blown Limiter Indicator light confirms short circuit and breaker trip
  • Integrated Breaker and Fuse design for superior power system coordination
  • Levering mechanisms for easy removal of breaker or truck
  • Trucks and Breakers physically fit in same compartment
  • DSL Trucks for Class L fuses allow separate draw-out mounting and heat isolation

Looking for an integrated circuit breaker and power fusing solution? DSL breakers and DSL breaker fuses are a coordinated combination of breakers and integrally mounted current limiting fuses.  Effective system coordination between the breaker and fuse prevents equipment damage and reduces arc flash hazard caused by short circuits and extremely high fault currents.  If you’re looking for integrated breaker and fusing for straightforward maintenance and proven reliability, Eaton Low Voltage Power Circuit Breakers Type DSL are a good choice.

Why Monster for Power Fuses and Controls?

Monster Fuses stocks fuses for EATON type DBL (Westinghouse) Breakers and DSL Breakers.


Eaton (Westinghouse) 6DSL A600 Type DBL

Eaton (Westinghouse) 6MDSL-MD2500 Type DSL

Eaton (Westinghouse) Eaton 6DSL-B1600 Type DSL

Eaton (Westinghouse) Eaton 6DSL-D3000 Type DSL

Eaton (Westinghouse) Eaton 6DSL-E4000 Type DSL

Eaton (Westinghouse) Eaton 6DSL-C1200 Type DSL
Eaton 4NPL-1875

Eaton (Westinghouse) Eaton 4NPL-1875 Type NPL

Monster Fuses also stocks breaker fuse solutions from EATON Cooper Bussmann, Mersen and Econolim for GE, ITE and other manufacturers. Tri-Pac, Molded Case, types K, KL, LA, NB, TB, PB, F and many more. Scroll through the fuse variations.

Power distribution systems come in all sizes and configurations and handle a wide range of currents. You can avoid fuse sizing mistakes when selecting and correctly sizing replacement fuses for power distribution systems. Proper fuse selection depends on many factors, so consult a professional engineer for your application.

Monster Electrical is a “knowledge-based” independent distributor of fuses, fuse hardware and control equipment. We don’t just ship boxes. Our product and application knowledge goes into every transaction.

Monster Fuses provides immediate shipment of power fuses and power fuse mountings from our extensive inventory. Clients can access more than 14,000 power fuse solutions provided from a stock of 100,000+ fuses, eliminate long factory power fuse lead times, and supply real time solutions for urgent fuse challenges in utility, industrial, institutional and commercial applications.

Need help calculating fuse current ratings for transformers or selecting fuse hardwarepower equipment and electrical replacement parts? Call 888-444-4335

Monster Controls: Looking for motor starterscontactors, isolation switches, and replacement parts? Call 888-820-4335.

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