Littelfuse 0255001.NRT2 Equivalent & Substitute Parts

Part Overview

The Littelfuse 0255001.NRT2 is a 1 A, 125 V AC/DC board mount axial fuse with fast blow response time, designed for through-hole applications. This component is classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support and procurement planning. The PICO® 255 series fuse has been superseded by newer product lines that maintain electrical and mechanical compatibility while offering improved availability and compliance status.

Key Parameters

Parameter	Value
Current Rating	1 A
Voltage Rating (AC)	125 V
Voltage Rating (DC)	125 V
Response Time	Fast Blow
Mounting Type	Through Hole
Fuse Type	Board Mount (Cartridge Style Excluded)
Package / Case	Axial
Breaking Capacity @ Rated Voltage	50 A AC, 300 A DC
Approval Agency	CSA, UL

Substitute Part Grouping Explanation

Substitution of the 0255001.NRT2 is determined by strict equivalence across the following electrical and mechanical parameters:

Current Rating: 1 A (exact match required)
Voltage Rating: 125 V AC and 125 V DC (exact match required)
Response Time: Fast Blow (exact match required)
Mounting Type: Through Hole (exact match required)
Package / Case: Axial (exact match required)
Breaking Capacity: 50 A AC, 300 A DC (exact match required)

The Littelfuse 0251001.NRT1L (PICO® II 251 series) meets all substitution criteria. While dimensional tolerances differ slightly (0.110" Dia vs. 0.095" Dia), both components maintain axial package geometry suitable for through-hole board mount applications. The substitute part is active in production with enhanced compliance certifications and improved thermal operating range.

Parameter Comparison

Parameter	0255001.NRT2 (Main Part)	0251001.NRT1L (Substitute)	Match Status
Manufacturer	Littelfuse Inc.	Littelfuse Inc.	Identical
Current Rating (Amps)	1 A	1 A	Equivalent
Voltage Rating - AC	125 V	125 V	Equivalent
Voltage Rating - DC	125 V	125 V	Equivalent
Response Time	Fast Blow	Fast Blow	Equivalent
Mounting Type	Through Hole	Through Hole	Equivalent
Fuse Type	Board Mount (Cartridge Style Excluded)	Board Mount (Cartridge Style Excluded)	Equivalent
Package / Case	Axial	Axial	Equivalent
Breaking Capacity @ Rated Voltage	50 A AC, 300 A DC	50 A AC, 300 A DC	Equivalent
Approval Agency	CSA, UL	CCC, CSA, cURus, PSE, TUV	Superset
Product Status	Obsolete	Active	Improved
RoHS Status	RoHS non-compliant	ROHS3 Compliant	Improved
Operating Temperature Range	Not specified	-55°C ~ 125°C	Specified
Size / Dimension	0.095" Dia x 0.280" L (2.41mm x 7.11mm)	0.110" Dia x 0.280" L (2.80mm x 7.11mm)	Minor variation

Engineering Selection Recommendations

The Littelfuse 0251001.NRT1L is the direct functional equivalent for the obsolete 0255001.NRT2. Selection of the substitute part is supported by:

Identical electrical performance across all rated parameters (current, voltage, response time, breaking capacity)
Active production status ensuring long-term availability and supply chain continuity
Enhanced regulatory compliance (ROHS3 Compliant vs. non-compliant; expanded approval agencies including CCC, cURus, PSE, TUV)
Specified operating temperature range (-55°C ~ 125°C) providing thermal performance documentation
Axial package geometry maintained for through-hole board mount compatibility

The minor dimensional increase in fuse diameter (0.095" to 0.110") does not affect electrical function and remains within standard axial package tolerances for through-hole applications. Mechanical fit verification in the target PCB layout is recommended prior to production implementation.

Frequently Asked Questions (FAQ)

Q: Can the 0251001.NRT1L be used as a direct replacement for the 0255001.NRT2?

A: Yes. Both components are electrically and mechanically equivalent across all specified parameters: 1 A current rating, 125 V AC/DC voltage rating, fast blow response, 50 A AC / 300 A DC breaking capacity, and through-hole axial package configuration.

Q: What is the significance of the dimensional difference (0.095" Dia vs. 0.110" Dia)?

A: The diameter increase of 0.015" remains within standard axial fuse package tolerances and does not affect electrical performance. PCB hole sizing and component placement should be verified to ensure mechanical fit in the target application.

Q: Why is the 0255001.NRT2 marked as obsolete?

A: The PICO® 255 series has been superseded by the PICO® II 251 series, which offers improved compliance certifications (ROHS3 Compliant), expanded regulatory approvals, and documented thermal operating range. The substitute part provides equivalent functionality with enhanced product lifecycle support.

Q: Are there compliance differences between the two parts?

A: The 0251001.NRT1L provides expanded regulatory coverage (CCC, CSA, cURus, PSE, TUV) compared to the 0255001.NRT2 (CSA, UL). The substitute part is ROHS3 Compliant, whereas the main part is RoHS non-compliant. These improvements support broader market applications and regulatory requirements.

Q: What packaging formats are available for the 0251001.NRT1L?

A: The substitute part is available in Cut Tape (CT) packaging. Packaging format selection should align with assembly process requirements and inventory management practices.

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