Equivalent & Substitute Parts for 5SF 2.5 Glass Cartridge Fuse

Part Overview

The Bel Fuse Inc. 5SF 2.5 is a 2.5 A, 250 V AC/DC glass cartridge fuse in 5mm x 20mm form factor, designed for fast-blow protection in electrical circuits. This part is classified as obsolete, necessitating identification of active equivalent and substitute components that maintain electrical and mechanical compatibility. Substitute parts must match the core electrical ratings, physical dimensions, and mounting requirements to ensure direct replacement capability in existing fuse holders.

Substiute Parts

5SF 2.5

Bel Fuse Inc.In Stock: 11145SF 2.5 Datasheet

Current PartRFQ

5MF 2.5-R

Bel Fuse Inc.In Stock: 235925MF 2.5-R Datasheet

Parametric EquivalentRFQ

5SF 2.5-R

Bel Fuse Inc.In Stock: 27815SF 2.5-R Datasheet

Parametric EquivalentRFQ

0034.1520

SCHURTER Inc.In Stock: 157860034.1520 Datasheet

DirectRFQ

021702.5HXP

Littelfuse Inc.In Stock: 3559021702.5HXP Datasheet

DirectRFQ

021702.5MXP

Littelfuse Inc.In Stock: 3305021702.5MXP Datasheet

DirectRFQ

021702.5TXP

Littelfuse Inc.In Stock: 990021702.5TXP Datasheet

DirectRFQ

021702.5VXP

LittelfuseIn Stock: 830021702.5VXP Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 5SF 2.5 is determined by strict adherence to the following parameters:

Primary Matching Criteria (Non-Negotiable):

• Current Rating: 2.5 A
• Voltage Rating (AC): 250 V
• Fuse Type: Cartridge, Glass
• Response Time: Fast Blow
• Package / Case: 5mm x 20mm
• Mounting Type: Requires Holder
• Operating Temperature Range: -55°C to 125°C

Secondary Compatibility Factors:

• Breaking Capacity @ Rated Voltage: 35 A (primary specification)
• Melting I²t: 7.6 to 10.2 (acceptable range for fast-blow cartridge fuses)
• Physical Dimensions: 5.10mm to 5.20mm diameter, 20.00mm length

All substitute parts listed below satisfy these criteria and are classified as active products with current manufacturing status.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: Bel Fuse Inc. 5SF 2.5-R

The 5SF 2.5-R is the direct active equivalent of the obsolete 5SF 2.5. It maintains identical electrical ratings, breaking capacity, and physical dimensions while offering ROHS3 compliance and active product status. This part is the preferred replacement for direct substitution in existing applications.

Secondary Recommendations:

Littelfuse 021702.5MXP, 021702.5TXP, 021702.5HXP, 021702.5VXP (217 Series)

These Littelfuse cartridge fuses meet all primary matching criteria with identical current, voltage, and breaking capacity specifications. The 217 series offers broader international certification coverage (BSI, CE, CCC, CSA, KC, PSE, SEMKO, UR, VDE) and ROHS3 compliance. Melting I²t values (9.46) fall within the acceptable range for fast-blow operation.

SCHURTER 0034.1520 (FSF 5x20 Series)

The SCHURTER FSF 5x20 series part meets all electrical and mechanical requirements with equivalent breaking capacity and melting I²t characteristics. This option provides an alternative from a different manufacturer with active product status and ROHS3 compliance.

Alternative Option: Bel Fuse Inc. 5MF 2.5-R

The 5MF 2.5-R shares identical current and voltage ratings but features a higher breaking capacity of 200 A and lower melting I²t of 7.6. This part is suitable for applications where enhanced breaking capacity is beneficial, though it represents a design change from the original 35 A specification.

Frequently Asked Questions (FAQ)

Q: Can I use the 5MF 2.5-R as a direct replacement for the 5SF 2.5?

A: The 5MF 2.5-R is electrically compatible in terms of current and voltage ratings but differs in breaking capacity (200 A vs. 35 A) and melting I²t (7.6 vs. 10.2). It is a functional substitute where higher breaking capacity is acceptable or beneficial, but represents a specification change from the original design.

Q: Are all substitute parts physically compatible with existing 5mm x 20mm fuse holders?

A: Yes. All listed substitute parts conform to the 5mm x 20mm package specification and are designed for use with standard 5mm x 20mm fuse holders. Physical dimensions range from 5.10mm to 5.20mm diameter, which falls within normal manufacturing tolerances for this form factor.

Q: What is the significance of the melting I²t parameter in fuse selection?

A: Melting I²t defines the thermal energy required to melt the fuse element and is critical for coordination with circuit protection schemes. The substitute parts listed have melting I²t values between 7.6 and 10.2, all within the acceptable range for 2.5 A fast-blow cartridge fuses. Lower values indicate faster response; higher values indicate slightly slower response, but all remain classified as fast-blow.

Q: Which substitute offers the best compliance profile?

A: The Littelfuse 217 series (021702.5MXP, 021702.5TXP, 021702.5HXP, 021702.5VXP) offers the broadest international certification coverage, including BSI, CE, CCC, CSA, KC, PSE, SEMKO, UR, and VDE. All listed substitutes are ROHS3 compliant and REACH unaffected.

Q: Does the DC cold resistance difference between parts affect circuit performance?

A: DC cold resistance values range from 0.026 Ω to 0.0334 Ω across the substitute parts. These minimal differences have negligible impact on circuit operation in typical applications. Selection based on DC cold resistance alone is not a primary substitution criterion.

Q: What is the inventory status of these substitute parts?

A: All substitute parts are currently in active production with available inventory. The 5SF 2.5-R (2,698 pcs), 5MF 2.5-R (23,563 pcs), and Littelfuse 021702.5MXP (3,295 pcs) offer the highest stock levels for immediate procurement.