ECNR/ECSR Class RK5 Dual-Element Time-Delay Fuses

Bullet ™ Class RK5 Dual-Element Time-Delay Fuses/ ECNR-ECSR

These fuses are recommended for AC power distribution system mains, feeders and branch circuits having inductive loads (motors, transformers) or non-inductive loads (lighting, heating) where the available short-circuit current does not exceed 200,000 RMS symmetrical amps. These “dual-element, time-delay” fuses have minimum industry standard time-delay of 10 seconds at 5 times the fuse rating (8 sec. minimum for 250V, 30A and less). The time-delay characteristics of these fuses typically allows them to be sized closer to the running ampacity of inductive loads to reduce cost and provide improved overcurrent protection. These fuses will override normal equipment current surges to reduce unnecessary fuse openings. They are the most popular fuses used in the industry and the most economical for most applications, especially motors and transformers. They have moderate current limitation.


250V ECNR Data Sheets

Data Sheet #1315 (1-60 Amps)

Data Sheet # 1316 (70-600 Amps)

600 Volt ECSR Data Sheets

Data Sheet # 1317 (1-60 Amps)

Data Sheet #1318 (70-600 Amps)




Catalog Number ECNR, ECSR
Volts - ECNR - 250V
- ECSR - 600Vac
Amps 1 - 600A
Interrupting Rating 200kA RMS Sym
Agency Approvals UL Listed, Class RK5, Guide JDDZ, File E162363; CSA Certified, C22.2, No. 248.12, Class 1422-02, File 700489


Voltage Rating: ECNR (1-60A, 110-200A) 125Vdc; (225-600A) 250Vdc; ECSR (1-600A) 300Vdc

Interrupting Rating: ECNR/ECSR 20,000 Amps DC


  • True dual-element construction allows sizing of 125% FLA for motor backup protection.
  • Superior overload and cycling capabilities.
  • Current limiting provides component short-circuit protection.


  • Recommended for AC power distribution system mains,feeders, and branch circuits.
  • Protection of motors and motor branch circuits.
  • Protection of transformers and other inductive loads.
  • All general-purpose applications including lighting, heating and other non-inductive loads.

Recommended Upgrade:

Class RK1 (LENRK/LESRK) for greater degree of short-circuit protection.