Littelfuse 0251004.NRT2 Equivalent & Substitute Parts

Part Overview

The Littelfuse 0251004.NRT2 is a 4 A, 125 V AC/DC board mount axial fuse from the PICO® II 251 series. This part is classified as obsolete, making equivalent substitutes necessary for new designs and ongoing production requirements. The fuse is designed for through-hole mounting applications requiring fast-blow response characteristics with a 50 A AC and 300 A DC breaking capacity at rated voltage.

Key Parameters

Parameter	Value
Current Rating	4 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
Melting I²t	2.45
Operating Temperature Range	-55°C to 125°C
DC Cold Resistance	0.0204 Ohms
Size / Dimension	0.110" Dia x 0.280" L (2.80 mm x 7.11 mm)

Substitute Part Grouping Explanation

Substitution for the 0251004.NRT2 is determined by strict equivalence across the following parameters:

Current Rating: 4 A
Voltage Rating: 125 V AC and 125 V DC
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
Melting I²t: 2.45
Operating Temperature Range: -55°C to 125°C
DC Cold Resistance: 0.0204 Ohms
Size / Dimension: 0.110" Dia x 0.280" L (2.80 mm x 7.11 mm)

All Littelfuse PICO® II 251 series parts listed below meet these electrical and mechanical parameters. Differences exist only in packaging format and product status. The SCHURTER 7010.7120.13 is a direct functional equivalent with minor dimensional and breaking capacity variations.

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating	Voltage (AC/DC)	Response Time	Breaking Capacity	Melting I²t	Operating Temp	DC Resistance	Packaging	Product Status	RoHS Status
0251004.NRT2	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Axial	Obsolete	Non-compliant
0251004.MXL	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Bulk	Active	ROHS3 Compliant
0251004.HAT1L	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Cut Tape (CT)	Active	ROHS3 Compliant
0251004.MAT1L	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Cut Tape (CT)	Active	ROHS3 Compliant
0251004.MRT1L	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Cut Tape (CT)	Active	ROHS3 Compliant
0251004.NAT1L	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Cut Tape (CT)	Active	ROHS3 Compliant
0251004.NRT1L	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Cut Tape (CT)	Active	ROHS3 Compliant
0251004.PARL	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Tape & Reel (TR)	Active	ROHS3 Compliant
0251004.PAT1L	Littelfuse	PICO® II 251	4 A	125 V / 125 V	Fast Blow	50 A AC, 300 A DC	2.45	-55°C to 125°C	0.0204 Ω	Tape & Box (TB)	Active	ROHS3 Compliant
0491004.MAT1	Littelfuse	PICO® II 491	4 A	125 V / 125 V	Fast Blow	50 A AC	Not specified	-55°C to 125°C	0.0204 Ω	Not specified	Active	ROHS3 Compliant
7010.7120.13	SCHURTER	172322	4 A	125 V / 125 V	Fast Blow	300 A DC	4	-55°C to 85°C	0.0204 Ω	Bulk	Active	ROHS3 Compliant

Engineering Selection Recommendations

For applications requiring the 0251004.NRT2, the following selection criteria apply:

Primary Recommendation: 0251004.MXL This part is the manufacturer-recommended substitute. It maintains full electrical and mechanical equivalence with active product status and ROHS3 compliance. Bulk packaging is suitable for production environments.

Alternative Littelfuse PICO® II 251 Series (0251004.HAT1L, 0251004.MAT1L, 0251004.MRT1L, 0251004.NAT1L, 0251004.NRT1L, 0251004.PARL, 0251004.PAT1L) All parts in this group are parametrically equivalent with identical electrical specifications. Selection among these variants depends on packaging requirements:

Cut Tape (CT): 0251004.HAT1L, 0251004.MAT1L, 0251004.MRT1L, 0251004.NAT1L, 0251004.NRT1L
Tape & Reel (TR): 0251004.PARL
Tape & Box (TB): 0251004.PAT1L

All are active products with ROHS3 compliance and CSA, cURus, PSE, TUV certifications.

Alternative Littelfuse PICO® II 491 Series (0491004.MAT1) This part shares identical electrical ratings and operating temperature range. It differs in series designation and certification scope (CSA, PSE, UL only). Use only when PICO® II 491 series compatibility is required.

Cross-Manufacturer Alternative: SCHURTER 7010.7120.13 This part provides functional equivalence with 4 A, 125 V AC/DC ratings and fast-blow response. Differences include:

Operating temperature upper limit: 85°C (versus 125°C for Littelfuse)
Melting I²t: 4 (versus 2.45 for Littelfuse)
Breaking capacity: 300 A DC only (versus 50 A AC, 300 A DC for Littelfuse)
Physical dimensions: 0.093" Dia x 0.315" L (versus 0.110" Dia x 0.280" L)

Use only when mechanical fit and thermal requirements align with SCHURTER specifications.

Frequently Asked Questions (FAQ)

Q: Can I use 0251004.MXL as a direct replacement for 0251004.NRT2? A: Yes. The 0251004.MXL is the manufacturer-recommended substitute with identical electrical and mechanical specifications. The only difference is packaging format (Bulk versus the original packaging) and product status (Active versus Obsolete).

Q: What is the difference between the various Littelfuse PICO® II 251 packaging options? A: All PICO® II 251 variants listed (0251004.HAT1L, 0251004.MAT1L, 0251004.MRT1L, 0251004.NAT1L, 0251004.NRT1L, 0251004.PARL, 0251004.PAT1L) are electrically and mechanically identical. Differences exist only in packaging format: Cut Tape (CT), Tape & Reel (TR), Tape & Box (TB), or Bulk. Select based on your assembly process requirements.

Q: Is the SCHURTER 7010.7120.13 a suitable replacement? A: The SCHURTER part meets the core electrical requirements (4 A, 125 V AC/DC, fast-blow). However, it has a lower maximum operating temperature (85°C versus 125°C), different melting I²t (4 versus 2.45), and different physical dimensions. Use only if your application requirements align with these specifications.

Q: What does RoHS3 compliance mean for my application? A: ROHS3 compliance indicates the part meets Restriction of Hazardous Substances Directive requirements. The original 0251004.NRT2 is non-compliant. All active substitutes listed are ROHS3 compliant, making them suitable for applications requiring RoHS compliance.

Q: Can I use 0491004.MAT1 from the PICO® II 491 series? A: The 0491004.MAT1 shares identical electrical ratings and operating temperature range with the 0251004.NRT2. However, it belongs to a different series with different certifications (CSA, PSE, UL versus CCC, CSA, cURus, PSE, TUV). Use only if your design specifications permit PICO® II 491 series components.

Q: Why is the original 0251004.NRT2 marked as obsolete? A: Obsolete status indicates the part is no longer manufactured. Active substitutes from the same PICO® II 251 series provide full functional equivalence and are recommended for all new designs and production requirements.

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