3AP 2.5-R Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 3AP 2.5-R is a 2.5 A, 250 V AC/DC fast-blow glass cartridge fuse in 3AB/3AG package format (1/4" x 1-1/4" axial). This component is classified as obsolete, making equivalent substitute parts necessary for ongoing system maintenance and new design implementations. Littelfuse Inc. Series 318 fuses provide direct functional equivalents with active product status and expanded certification coverage.

Substiute Parts

3AP 2.5-R

Bel Fuse Inc.In Stock: 11723AP 2.5-R Datasheet

Current PartRFQ

031802.5HXP

Littelfuse Inc.In Stock: 976031802.5HXP Datasheet

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031802.5MXP

Littelfuse Inc.In Stock: 791031802.5MXP Datasheet

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031802.5VXP

Littelfuse Inc.In Stock: 1017031802.5VXP Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 3AP 2.5-R is determined by strict equivalence across the following parameters:

• Current Rating: 2.5 A (exact match required)
• Voltage Rating: 250 V AC (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Response Time: Fast Blow (exact match required)
• Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (exact match required)
• Mounting Type: Through Hole (exact match required)
• Operating Temperature Range: -55°C ~ 125°C (exact match required)

All three Littelfuse Series 318 parts (031802.5HXP, 031802.5MXP, 031802.5VXP) meet these criteria and are qualified substitutes. Variations in Breaking Capacity, Melting I²t, and DC Cold Resistance do not disqualify substitution when all primary electrical and mechanical parameters align.

Parameter Comparison

Engineering Selection Recommendations

All three Littelfuse Series 318 substitutes (031802.5HXP, 031802.5MXP, 031802.5VXP) are qualified replacements for the obsolete 3AP 2.5-R. Selection among these three interchangeable parts should be based on:

• Availability: 031802.5VXP (929 pcs), 031802.5HXP (950 pcs), 031802.5MXP (714 pcs)
• Certification requirements: All three carry CE, CSA, KC, PSE, and UL approvals, exceeding the original part's CE, CSA, cULus, and PSE certifications
• RoHS3 compliance: All substitutes maintain regulatory compliance equivalent to the original part

The Littelfuse parts feature slightly higher dimensional tolerances (0.275" Dia x 1.288" L versus 0.272" Dia x 1.280" L) and lower Breaking Capacity (100A versus 200A), but these variations remain within acceptable substitution parameters for 2.5 A, 250 V AC/DC fast-blow cartridge fuse applications.

Frequently Asked Questions (FAQ)

Q: Can 031802.5HXP, 031802.5MXP, and 031802.5VXP be used interchangeably with 3AP 2.5-R?

A: Yes. All three Littelfuse parts are direct functional equivalents. They share identical current rating (2.5 A), voltage rating (250 V AC), fuse type (cartridge glass), response time (fast blow), package format (3AB/3AG), and mounting type (through hole). Physical dimensions and electrical characteristics are within acceptable tolerance for this component category.

Q: What is the difference between 031802.5HXP, 031802.5MXP, and 031802.5VXP?

A: These three part numbers are electrically and mechanically identical. Differences exist only in packaging designation and internal manufacturing specifications. All three are Series 318 fuses with active product status and equivalent performance characteristics.

Q: Why does the 3AP 2.5-R have higher Breaking Capacity (200A) than the Littelfuse substitutes (100A)?

A: Breaking Capacity represents the maximum current the fuse can safely interrupt without rupturing. The 3AP 2.5-R specification of 200A exceeds typical application requirements for 2.5 A fuses. The Littelfuse 100A Breaking Capacity remains adequate for standard 2.5 A, 250 V AC/DC circuit protection applications.

Q: Are the dimensional differences between 3AP 2.5-R and Littelfuse Series 318 significant?

A: Dimensional variations (0.272" Dia x 1.280" L versus 0.275" Dia x 1.288" L) are within standard manufacturing tolerances for 3AB/3AG cartridge fuses. Both sets of dimensions conform to the 1/4" x 1-1/4" axial package specification and are mechanically compatible with standard fuse holders.

Q: Do the Littelfuse substitutes carry the same certifications as the original 3AP 2.5-R?

A: The Littelfuse Series 318 substitutes carry expanded certification coverage (CE, CSA, KC, PSE, UL) compared to the original part (CE, CSA, cULus, PSE). This provides equivalent or superior regulatory compliance for most applications.

Q: Is the DC Cold Resistance difference (0.047 Ohms versus 0.0513 Ohms) significant?

A: The DC Cold Resistance variation is minimal and does not affect substitution eligibility. Both values are within acceptable ranges for 2.5 A cartridge fuses and do not impact circuit protection performance in standard applications.