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S505-1.25-R Ceramic Fuse Equivalent & Substitute Parts
Part Overview
The S505-1.25-R is a 1.25 A, 250 V AC ceramic cartridge fuse manufactured by Eaton - Electronics Division. This slow-blow fuse is designed for 5mm x 20mm holder applications and requires an external fuse holder for installation. The part is active in production with 824 pieces currently in stock. Equivalent and substitute parts are identified based on matching electrical ratings, mechanical dimensions, response characteristics, and approval certifications to ensure direct functional interchangeability in circuit protection applications.
Substiute Parts
Key Parameters
| Parameter | Value |
|---|---|
| Current Rating | 1.25 A |
| Voltage Rating - AC | 250 V |
| Fuse Type | Cartridge, Ceramic |
| Response Time | Slow Blow |
| Package / Case | 5mm x 20mm |
| Breaking Capacity @ Rated Voltage | 1.5 kA |
| Mounting Type | Requires Holder |
| Size / Dimension | 0.205" Dia x 0.787" L (5.20mm x 20.00mm) |
Substitute Part Grouping Explanation
Substitute parts for the S505-1.25-R are grouped into two categories based on electrical and mechanical compatibility:
Direct Manufacturer Equivalents (Eaton - Electronics Division): Parts BK/S505-1.25-R and BK1/S505-1.25-R are direct variants from the same manufacturer and series. These parts maintain identical electrical specifications: 1.25 A current rating, 250 V AC voltage rating, slow-blow response, 1.5 kA breaking capacity, and 5mm x 20mm package dimensions. Substitution is based on matching all critical electrical parameters and mechanical form factor.
Cross-Manufacturer Parametric Equivalents: Parts from Littelfuse Inc. (02151.25MXP, 02151.25HXP, 02151.25TXP), SCHURTER Inc. (0001.2505, 0001.2705.11), Bel Fuse Inc. (0659C1250-12), and OptiFuse (TCD-1.25A) are functionally equivalent based on the following criteria:
- Current Rating: 1.25 A
- Voltage Rating - AC: 250 V
- Fuse Type: Cartridge, Ceramic
- Response Time: Slow Blow
- Package / Case: 5mm x 20mm
- Breaking Capacity @ Rated Voltage: 1.5 kA
- Mounting Type: Requires Holder
- Physical Dimensions: 0.205" Dia x 0.787" L (5.20mm x 20.00mm)
Substitution eligibility is determined by exact matching of these parameters. Variations in melting I²t, DC cold resistance, operating temperature range, and approval agencies do not preclude substitution when all primary electrical and mechanical parameters align.
Parameter Comparison
| Part Number | Manufacturer | Current Rating (A) | Voltage - AC (V) | Fuse Type | Response Time | Package (mm) | Breaking Capacity (kA) | Melting I²t | DC Cold Resistance (Ohms) | Operating Temperature | RoHS Status |
|---|---|---|---|---|---|---|---|---|---|---|---|
| S505-1.25-R | Eaton - Electronics Division | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 2.22 | 0.1075 | Not specified | RoHS Compliant |
| BK/S505-1.25-R | Eaton - Electronics Division | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 2.22 | 0.1075 | Not specified | ROHS3 Compliant |
| BK1/S505-1.25-R | Eaton - Electronics Division | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 2.22 | 0.1075 | Not specified | RoHS Compliant |
| 02151.25MXP | Littelfuse Inc. | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 3.2 | 0.1074 | -55°C ~ 125°C | ROHS3 Compliant |
| 02151.25HXP | Littelfuse Inc. | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 3.2 | 0.1074 | -55°C ~ 125°C | ROHS3 Compliant |
| 02151.25TXP | Littelfuse Inc. | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 3.2 | 0.1074 | -55°C ~ 125°C | ROHS3 Compliant |
| 0001.2505 | SCHURTER Inc. | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 1.86 | Not specified | -55°C ~ 125°C | ROHS3 Compliant |
| 0001.2705.11 | SCHURTER Inc. | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 1.86 | Not specified | -55°C ~ 125°C | ROHS3 Compliant |
| 0659C1250-12 | Bel Fuse Inc. | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | 3.3 | 0.103 | -55°C ~ 125°C | ROHS3 Compliant |
| TCD-1.25A | OptiFuse | 1.25 | 250 | Cartridge, Ceramic | Slow Blow | 5 x 20 | 1.5 | Not specified | Not specified | -55°C ~ 125°C | RoHS Compliant |
Engineering Selection Recommendations
Eaton Direct Variants (BK/S505-1.25-R, BK1/S505-1.25-R): These parts are recommended as primary substitutes due to identical electrical specifications, mechanical dimensions, and series designation. Both variants maintain the same 1.25 A current rating, 250 V AC voltage rating, slow-blow response, and 1.5 kA breaking capacity. BK/S505-1.25-R carries ROHS3 compliance, while BK1/S505-1.25-R maintains RoHS compliance. Both are active products with adequate inventory availability.
Littelfuse 215 Series (02151.25MXP, 02151.25HXP, 02151.25TXP): These parts are functionally equivalent with identical electrical and mechanical parameters. All three variants are ROHS3 compliant and carry expanded operating temperature specifications (-55°C ~ 125°C). Approval certifications include CCC, CE, CSA, KC, PSE, SEMKO, UL, and VDE. Melting I²t values of 3.2 differ from the main part but remain within acceptable substitution parameters. High inventory availability (2,300 to 5,100 pieces) supports supply chain continuity.
SCHURTER SPT Series (0001.2505, 0001.2705.11): These parts meet all primary electrical and mechanical substitution criteria with 1.25 A current rating, 250 V AC voltage rating, and 5mm x 20mm package dimensions. Both are ROHS3 compliant with operating temperature range of -55°C ~ 125°C. The 0001.2705.11 is a variant of the base product 0001.2705. Melting I²t values of 1.86 differ from the main part. Approval certifications include CCC, cURus, KC, PSE/JET, and VDE. Inventory availability is substantial (1,033 to 12,134 pieces).
Bel Fuse 0659C Series (0659C1250-12): This part is functionally equivalent with matching electrical specifications and 5mm x 20mm package dimensions. ROHS3 compliance and operating temperature range of -55°C ~ 125°C are provided. Approval certifications include CCC, cURus, PSE, and VDE. Melting I²t value of 3.3 and DC cold resistance of 0.103 Ohms differ slightly from the main part. Inventory availability is 2,019 pieces.
OptiFuse TCD Series (TCD-1.25A): This part meets all primary electrical and mechanical substitution criteria with 1.25 A current rating, 250 V AC voltage rating, and 5mm x 20mm package dimensions. RoHS compliance and operating temperature range of -55°C ~ 125°C are provided. Approval certifications include cURus and IEC 60127. Inventory availability is 4,684 pieces.
Frequently Asked Questions (FAQ)
Q: What determines if a fuse can substitute for the S505-1.25-R?
A: Substitution eligibility is based on matching the following parameters: 1.25 A current rating, 250 V AC voltage rating, ceramic cartridge fuse type, slow-blow response time, 5mm x 20mm package dimensions, 1.5 kA breaking capacity, and holder-based mounting type. All listed substitute parts meet these criteria.
Q: Are there differences in melting I²t values among the substitute parts?
A: Yes. The main part S505-1.25-R has a melting I²t of 2.22. Littelfuse parts (02151.25MXP, 02151.25HXP, 02151.25TXP) have 3.2, SCHURTER parts (0001.2505, 0001.2705.11) have 1.86, and Bel Fuse 0659C1250-12 has 3.3. These variations do not preclude substitution when all primary electrical and mechanical parameters match.
Q: Can I use a substitute part with a different operating temperature range?
A: The main part S505-1.25-R does not specify an operating temperature range. Substitute parts with specified ranges (-55°C ~ 125°C) are compatible for applications within those temperature limits. Selection should be based on application requirements.
Q: What is the difference between the Eaton variants BK/S505-1.25-R and BK1/S505-1.25-R?
A: Both are direct Eaton equivalents with identical electrical specifications and mechanical dimensions. The primary difference is RoHS compliance status: BK/S505-1.25-R is ROHS3 compliant, while BK1/S505-1.25-R is RoHS compliant. Both are active products suitable for substitution.
Q: Do all substitute parts have the same approval certifications?
A: No. Approval certifications vary by manufacturer. The main part S505-1.25-R carries BSI, CCC/CQC, CSA, cULus, IMQ, KC, PSE/JET, SEMKO, and VDE certifications. Substitute parts carry different certification combinations. Selection should be based on application regulatory requirements.
Q: Are the SCHURTER parts 0001.2505 and 0001.2705.11 interchangeable?
A: Yes. Both parts have identical electrical specifications (1.25 A, 250 V AC), ceramic cartridge fuse type, slow-blow response, 5mm x 20mm package dimensions, and 1.5 kA breaking capacity. The 0001.2705.11 is a variant of base product 0001.2705. Both are suitable substitutes for the S505-1.25-R.
Q: What is the significance of DC cold resistance differences?
A: DC cold resistance values vary slightly among substitute parts (ranging from 0.103 to 0.1075 Ohms). These variations are within acceptable tolerances for ceramic cartridge fuses and do not affect substitution eligibility when all primary electrical and mechanical parameters match.
Q: Which substitute part has the highest inventory availability?
A: SCHURTER 0001.2505 has the highest inventory with 12,134 pieces in stock, followed by OptiFuse TCD-1.25A with 4,684 pieces and Littelfuse 02151.25MXP with 5,100 pieces.
Q: Can I substitute the S505-1.25-R with a part rated for higher voltage?
A: Substitution must be based on matching the specified 250 V AC voltage rating. Parts rated for higher voltages are not listed as substitutes for this application. Use only parts with 250 V AC rating to maintain circuit protection integrity.
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