SR-5-1.25A-AP Board Mount Fuse Equivalent & Substitute Parts

Part Overview

The SR-5-1.25A-AP is a 1.25 A, 250 V AC/DC board mount fuse manufactured by Eaton - Electronics Division. This radial, can-style through-hole fuse features slow-blow response characteristics and is designed for circuit protection applications requiring moderate inrush current tolerance. The part is currently active in production with 1882 units in stock. Equivalent and substitute parts are identified to support procurement flexibility, inventory management, and supply chain continuity for applications where the original part may be unavailable or where alternative manufacturers' products meet identical electrical and mechanical specifications.

Substiute Parts

SR-5-1.25A-AP

Eaton - Electronics DivisionIn Stock: 1985SR-5-1.25A-AP Datasheet

Current PartRFQ

37211250001

Littelfuse Inc.In Stock: 2112637211250001 Datasheet

DirectRFQ

37011250000

Littelfuse Inc.In Stock: 1033537011250000 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of board mount fuses is determined by strict equivalence across electrical and mechanical parameters. The primary criteria for substitution are:

Electrical Parameters:

• Current Rating: 1.25 A (exact match required)
• Voltage Rating (AC): 250 V (exact match required)
• Breaking Capacity @ Rated Voltage: 35 A (exact match required)
• Operating Temperature Range: -40°C ~ 85°C (exact match required)

Mechanical Parameters:

• Mounting Type: Through Hole (exact match required)
• Fuse Type: Board Mount (Cartridge Style Excluded) (exact match required)
• Package / Case: Radial, Can, Vertical (exact match required)
• Size / Dimension: 0.335" Dia x 0.319" H / 8.50mm x 8.10mm (exact match required)

Response Characteristic:

• Response Time: Slow Blow (exact match required for direct equivalence)

The substitute parts identified below meet all electrical and mechanical parameters. Variations in melting I²t, DC cold resistance, and dimensional tolerances within the specified range do not affect functional substitution for this application category.

Parameter Comparison

Engineering Selection Recommendations

Direct Equivalent (Preferred Substitute):

The Littelfuse 37211250001 (TR5® 372 series) is a direct functional equivalent to the SR-5-1.25A-AP. Both parts share identical electrical ratings (1.25 A, 250 V AC), slow-blow response characteristics, breaking capacity (35 A), and operating temperature range (-40°C ~ 85°C). Dimensional differences are within acceptable manufacturing tolerances for through-hole radial can fuses (height variation of 0.004" / 0.10mm). Both parts carry equivalent regulatory approvals (CCC, PSE, SEMKO, VDE) and are RoHS compliant. The 37211250001 offers superior inventory availability (21100 units in stock) and ROHS3 compliance status.

Alternative Substitute (Application-Dependent):

The Littelfuse 37011250000 (TR5® 370 series) meets all mechanical and electrical parameters but features fast-blow response characteristics instead of slow-blow. This part is suitable only for applications where fast-blow response is acceptable or required. The fast-blow characteristic (melting I²t of 0.31 versus 13 for slow-blow) results in faster circuit interruption with minimal inrush current tolerance. Selection of this part requires confirmation that the application circuit does not require the inrush current tolerance provided by slow-blow fuses.

Compliance Considerations:

All three parts carry CCC, PSE, SEMKO, and VDE certifications. The SR-5-1.25A-AP additionally carries cULus and KC-MARK approvals. The Littelfuse alternatives carry cURus approval. For applications requiring specific regional certifications, verify that the selected substitute meets all mandatory approval requirements for the target market.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 37211250001 be used as a direct replacement for the SR-5-1.25A-AP?

A: Yes. The 37211250001 is a direct functional equivalent. Both parts have identical current rating (1.25 A), voltage rating (250 V AC), response time (slow-blow), breaking capacity (35 A), mounting type (through-hole), package style (radial can vertical), and operating temperature range (-40°C ~ 85°C). Dimensional tolerances are within acceptable limits for this product category.

Q: What is the difference between the Littelfuse 37211250001 and 37011250000?

A: The primary difference is response time. The 37211250001 is slow-blow (melting I²t of 13.75), while the 37011250000 is fast-blow (melting I²t of 0.31). Both share identical current, voltage, breaking capacity, and mechanical specifications. The fast-blow characteristic of the 37011250000 provides faster circuit interruption but offers no inrush current tolerance. Selection depends on application requirements.

Q: Are there dimensional compatibility issues when substituting these parts?

A: Dimensional differences are minimal and within acceptable manufacturing tolerances. The SR-5-1.25A-AP measures 0.335" Dia x 0.319" H (8.50mm x 8.10mm). The Littelfuse alternatives measure 0.335" Dia x 0.315" H (8.50mm x 8.00mm). The height difference of 0.004" (0.10mm) does not affect through-hole mounting compatibility or PCB layout.

Q: Do all substitute parts carry the same regulatory approvals?

A: The SR-5-1.25A-AP carries CCC, cULus, KC-MARK, PSE, SEMKO, and VDE approvals. The Littelfuse 37211250001 and 37011250000 carry CCC, cURus, PSE, SEMKO, and VDE approvals. The SR-5-1.25A-AP includes KC-MARK certification, which the Littelfuse parts do not. For applications requiring KC-MARK certification, the original part must be used. For other markets, the Littelfuse alternatives meet equivalent regulatory requirements.

Q: What is the difference between RoHS and ROHS3 compliance?

A: Both indicate RoHS compliance. RoHS Compliant indicates compliance with the original RoHS Directive (2002/95/EC). ROHS3 Compliant indicates compliance with RoHS Recast (Directive 2011/65/EU as amended). ROHS3 is the current standard and includes additional restricted substances. Both compliance levels are acceptable for new designs; ROHS3 is preferred for long-term supply chain stability.

Q: Can I use the fast-blow 37011250000 in place of the slow-blow SR-5-1.25A-AP?

A: Only if the application circuit does not require inrush current tolerance. The fast-blow response (melting I²t of 0.31) will interrupt circuits much faster than the slow-blow response (melting I²t of 13). If the application has inrush current requirements (such as motor startup or transformer energization), the fast-blow fuse will nuisance trip. Verify application requirements before substitution.

Q: Which substitute part should I select for new designs?

A: The Littelfuse 37211250001 (TR5® 372) is recommended for new designs. It provides direct functional equivalence to the SR-5-1.25A-AP with superior inventory availability (21100 units in stock), ROHS3 compliance, and equivalent regulatory approvals for most markets. Use the SR-5-1.25A-AP only if KC-MARK certification is a mandatory requirement.