Equivalent & Substitute Parts for S501-1.25-R Ceramic Fuse

Part Overview

The S501-1.25-R is a ceramic cartridge fuse manufactured by Eaton - Electronics Division, rated at 1.25 A, 250 V AC/DC with fast-blow response characteristics. This component is designed for circuit protection in applications requiring a 5mm x 20mm form factor and operates within a breaking capacity of 1.5 kA at rated voltage. The part maintains Active product status with ROHS3 compliance and multiple international approvals including CCC, cURus, MITI/JET, and SEMKO certifications.

Equivalent and substitute parts are necessary when the primary part becomes unavailable, when supply chain optimization is required, or when alternative manufacturers offer identical electrical and mechanical specifications within the same product category.

Substiute Parts

S501-1.25-R

Eaton - Electronics DivisionIn Stock: 721S501-1.25-R Datasheet

Current PartRFQ

BK/S501-1.25-R

Eaton - Electronics DivisionIn Stock: 930BK/S501-1.25-R Datasheet

Parametric EquivalentRFQ

02161.25MXP

Littelfuse Inc.In Stock: 199002161.25MXP Datasheet

DirectRFQ

0001.1005

SCHURTER Inc.In Stock: 19240001.1005 Datasheet

Parametric EquivalentRFQ

02161.25HXP

Littelfuse Inc.In Stock: 854402161.25HXP Datasheet

Parametric EquivalentRFQ

FCD-1.25A

OptiFuseIn Stock: 3360FCD-1.25A Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the S501-1.25-R is determined by strict equivalence across the following critical parameters:

Mandatory Matching Parameters:

• Current Rating: 1.25 A (exact match required)
• Voltage Rating - AC: 250 V (exact match required)
• Fuse Type: Cartridge, Ceramic (exact match required)
• Response Time: Fast Blow (exact match required)
• Package / Case: 5mm x 20mm (exact match required)
• Breaking Capacity @ Rated Voltage: 1.5 kA (exact match required)
• Mounting Type: Requires Holder (exact match required)

All substitute parts listed below meet these mandatory parameters. Variations in secondary parameters such as melting I²t, DC cold resistance, operating temperature range, and approval agency certifications do not disqualify substitution but indicate manufacturer-specific design characteristics.

Parameter Comparison

Engineering Selection Recommendations

Primary Equivalent (Same Manufacturer): BK/S501-1.25-R from Eaton - Electronics Division is the direct parametric equivalent with identical electrical characteristics and mechanical specifications. This part carries the same approval agencies (CCC, cULus, MITI/JET, SEMKO) and maintains Active product status. Selection of this part eliminates any cross-manufacturer compatibility considerations.

Cross-Manufacturer Equivalents: All listed substitute parts (02161.25MXP, 02161.25HXP, 0001.1005, FCD-1.25A) meet the mandatory parameter requirements and maintain ROHS3 compliance. Each manufacturer provides Active product status with established international certifications:

• Littelfuse Inc. parts (02161.25MXP, 02161.25HXP) carry comprehensive approvals including CE, CSA, KC, PSE, SEMKO, UL, and VDE with specified operating temperature range of -55°C to 125°C.
• SCHURTER Inc. part (0001.1005) carries CCC, cURus, KC, and VDE approvals with operating temperature range of -55°C to 125°C.
• OptiFuse part (FCD-1.25A) carries IEC 60127 approval with operating temperature range of -55°C to 125°C.

Selection among cross-manufacturer equivalents should be based on supply availability, approval agency requirements for the end application, and inventory levels. All parts are suitable for direct substitution in applications where the S501-1.25-R is specified.

Frequently Asked Questions (FAQ)

Q: Can I substitute the S501-1.25-R with any of the listed equivalent parts?

A: Yes. All listed parts meet the mandatory electrical and mechanical parameters: 1.25 A current rating, 250 V AC voltage rating, fast-blow ceramic cartridge fuse type, 5mm x 20mm package, and 1.5 kA breaking capacity. Direct substitution is permissible from an electrical standpoint.

Q: What is the difference between the S501-1.25-R and BK/S501-1.25-R?

A: Both parts are manufactured by Eaton - Electronics Division and share identical electrical specifications and mechanical dimensions. The BK designation indicates a different packaging or distribution variant. Both are equivalent for circuit protection applications.

Q: Why do the substitute parts have different melting I²t values?

A: Melting I²t represents the thermal energy required to melt the fuse element and is a manufacturer-specific characteristic. Variations in melting I²t (ranging from 0.313 to 0.538 in the listed parts) reflect different internal fuse element designs while maintaining the same fast-blow response classification and 1.25 A current rating. These variations do not affect substitution eligibility.

Q: Do all substitute parts have the same approval certifications?

A: No. While all parts maintain ROHS3 compliance and Active product status, approval agencies vary by manufacturer. The S501-1.25-R carries CCC, cURus, MITI/JET, and SEMKO approvals. Littelfuse parts carry additional certifications including CE, CSA, UL, and VDE. SCHURTER and OptiFuse parts carry different certification combinations. Verify that the selected substitute meets the specific approval requirements of your application.

Q: Can I use these parts interchangeably in the same circuit?

A: Yes, provided the circuit design does not depend on manufacturer-specific characteristics such as DC cold resistance or specific operating temperature ranges. All parts are mechanically compatible with standard 5mm x 20mm fuse holders and electrically equivalent for the specified 1.25 A, 250 V AC circuit protection function.

Q: What should I consider when selecting between Littelfuse 02161.25MXP and 02161.25HXP?

A: Both Littelfuse parts are parametric equivalents with identical electrical specifications, melting I²t (0.48), DC cold resistance (0.153 Ohms), and operating temperature range (-55°C to 125°C). Selection between these parts should be based on availability and inventory levels. The 02161.25HXP currently has higher inventory (8481 pcs) compared to 02161.25MXP (1952 pcs).

Q: Are there any DC voltage considerations for these fuses?

A: The S501-1.25-R is rated for 250 V AC/DC operation. The FCD-1.25A from OptiFuse explicitly specifies 250 V DC rating. Other manufacturers do not specify separate DC ratings but are suitable for DC applications within the 250 V rating. Verify DC application requirements with the specific manufacturer if critical to your design.