GDB-1.25A Equivalent & Substitute Parts

Part Overview

The GDB-1.25A is a 1.25 A, 250 V AC/DC fast-blow glass cartridge fuse manufactured by Eaton - Electronics Division. This fuse is designed for applications requiring overcurrent protection in a 5mm x 20mm form factor and operates with a breaking capacity of 35 A at rated voltage. The part is active in production with 1193 pieces in current inventory. Substitute parts are identified to provide alternative sourcing options when the primary part is unavailable or when design requirements necessitate different electrical characteristics or approval agency certifications.

Key Parameters

Parameter	Value
Current Rating	1.25 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Fast Blow
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	35 A (standard); 100 A (enhanced variants)
Melting I²t	0.84 to 2.23
DC Cold Resistance	0.0701 to 0.122 Ohms

Substitute Part Grouping Explanation

Substitute parts for the GDB-1.25A are grouped based on strict electrical and mechanical parameter equivalence. All substitute parts maintain the following core parameters identical to the main part:

Current Rating: 1.25 A
Voltage Rating (AC): 250 V
Fuse Type: Cartridge, Glass
Package / Case: 5mm x 20mm
Response Time: Fast Blow
Mounting Type: Requires Holder

Substitution is permitted when these parameters are matched. Secondary parameters such as breaking capacity, melting I²t, DC cold resistance, and approval agency certifications may vary between substitute parts. These variations are documented to allow selection based on specific application requirements and regulatory compliance needs.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Series	Current Rating (A)	Voltage Rating (V AC)	Package	Response Time	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ohms)	Inventory (Pcs)
GDB-1.25A	Eaton - Electronics Division	GDB	1.25	250	5x20mm	Fast Blow	35	0.84	0.096	1193
BK/GMA-1.25-R	Eaton - Electronics Division	GMA	1.25	250	5x20mm	Fast Blow	100	0.84	0.122	1110
BK/S500-1.25-R	Eaton - Electronics Division	S500	1.25	250	5x20mm	Fast Blow	35	0.84	0.096	832
BK1/S500-1.25-R	Eaton - Electronics Division	S500	1.25	250	5x20mm	Fast Blow	35	0.84	0.096	2212
S500-1.25-R	Eaton - Electronics Division	S500	1.25	250	5x20mm	Fast Blow	35	0.84	0.096	835
0034.1517	SCHURTER Inc.	FSF 5x20	1.25	250	5x20mm	Fast Blow	35	1.81	Not Specified	1951
02171.25HXP	Littelfuse Inc.	217	1.25	250	5x20mm	Fast Blow	35	2.23	0.0701	1500
02171.25MXP	Littelfuse Inc.	217	1.25	250	5x20mm	Fast Blow	35	2.23	0.0701	5025
02171.25VXP	Littelfuse Inc.	217	1.25	250	5x20mm	Fast Blow	35	2.23	0.0701	831
02351.25HXP	Littelfuse Inc.	235	1.25	250	5x20mm	Fast Blow	100	1.085	0.1055	1372
02351.25MXP	Littelfuse Inc.	235	1.25	250	5x20mm	Fast Blow	100	1.085	0.1055	2630

Engineering Selection Recommendations

Selection of substitute parts for the GDB-1.25A is determined by application-specific requirements for breaking capacity, thermal characteristics, and regulatory compliance.

Standard Substitutes (35 A Breaking Capacity, Matched Melting I²t):

The BK/S500-1.25-R, BK1/S500-1.25-R, and S500-1.25-R from Eaton - Electronics Division provide direct electrical equivalence to the GDB-1.25A with identical breaking capacity and melting I²t values. These parts are suitable for applications where VDE, BSI, CSA, and cULus certifications are required. The BK1/S500-1.25-R offers the highest inventory availability at 2212 pieces.

Enhanced Breaking Capacity Substitutes (100 A Breaking Capacity):

The BK/GMA-1.25-R from Eaton and the 02351.25HXP and 02351.25MXP from Littelfuse provide 100 A breaking capacity while maintaining the 1.25 A current rating and 250 V voltage rating. These parts are specified for applications requiring higher fault current withstand capability. The 02351.25MXP offers the highest inventory at 2630 pieces and includes UL, CSA, and PSE certifications.

Alternative Manufacturer Options:

The 02171.25HXP, 02171.25MXP, and 02171.25VXP from Littelfuse (Series 217) and the 0034.1517 from SCHURTER provide cross-manufacturer substitution with full electrical parameter equivalence. The Littelfuse 217 series parts feature the highest melting I²t value at 2.23 and the lowest DC cold resistance at 0.0701 Ohms. The 02171.25MXP provides the largest inventory pool at 5025 pieces and includes comprehensive international certifications (BSI, CE, CCC, CSA, KC, PSE, SEMKO, UR, VDE).

Regulatory Compliance Considerations:

Applications requiring specific approval agency certifications should reference the provided certification lists. The GDB-1.25A carries VDE and UR approvals. Substitute parts with expanded certification coverage (such as the Littelfuse 217 and 235 series with BSI, CE, CCC, CSA, KC, PSE, SEMKO, UR, and VDE) are suitable for multi-market applications.

Frequently Asked Questions (FAQ)

Q: Can the BK/GMA-1.25-R be used as a direct replacement for the GDB-1.25A?

A: The BK/GMA-1.25-R is electrically equivalent in current rating, voltage rating, package, and response time. The primary difference is the breaking capacity: 100 A versus 35 A. This higher breaking capacity does not prevent substitution; it provides enhanced fault current withstand capability. Substitution is valid when the application circuit can accommodate the higher breaking capacity specification.

Q: What is the significance of melting I²t variation among substitute parts?

A: Melting I²t is a thermal characteristic that defines the fuse's response to overcurrent conditions. The GDB-1.25A has a melting I²t of 0.84. Substitute parts range from 0.84 to 2.23. Higher melting I²t values indicate slower thermal response. Selection should match the application's overcurrent protection requirements. Parts with identical melting I²t (such as the Eaton S500 series at 0.84) provide the closest thermal equivalence.

Q: Are all substitute parts compatible with the same fuse holder as the GDB-1.25A?

A: All substitute parts specified maintain the identical 5mm x 20mm package dimension and cartridge glass fuse type. All require a fuse holder for mounting. Physical compatibility with existing fuse holders is confirmed by the matching package specification. Electrical compatibility is confirmed by the matching current rating, voltage rating, and response time.

Q: Which substitute part offers the best inventory availability?

A: The 02171.25MXP from Littelfuse (Series 217) provides the highest inventory at 5025 pieces. The BK1/S500-1.25-R from Eaton (Series S500) offers the second-highest availability at 2212 pieces. Both parts are active in production and provide full electrical equivalence to the GDB-1.25A.

Q: What approval agencies are common across all substitute parts?

A: CSA and VDE certifications are present across multiple substitute parts. However, no single approval agency certification is universal to all listed substitutes. Applications requiring specific regulatory compliance should cross-reference the approval agency list for each candidate part.

Q: Can substitute parts with 100 A breaking capacity be used in applications designed for 35 A breaking capacity?

A: Yes. A higher breaking capacity specification does not restrict use in applications designed for lower breaking capacity. The 100 A breaking capacity parts (BK/GMA-1.25-R, 02351.25HXP, 02351.25MXP) provide enhanced fault current withstand capability and are suitable for any application requiring 35 A or lower breaking capacity.

Q: How do DC cold resistance variations affect part selection?

A: DC cold resistance ranges from 0.0701 Ohms (Littelfuse 217 series) to 0.122 Ohms (Eaton BK/GMA-1.25-R). Lower resistance reduces voltage drop across the fuse during normal operation. Selection based on DC cold resistance is application-specific and depends on circuit voltage drop requirements. The GDB-1.25A specifies 0.096 Ohms; substitute parts with similar values (0.096 Ohms) provide the closest thermal and electrical match.

Q: Are RoHS and REACH compliance requirements met by all substitute parts?

A: Most substitute parts carry RoHS3 compliance and REACH Unaffected status. The GDB-1.25A does not specify RoHS or REACH status in the provided data. Applications requiring explicit RoHS3 compliance should select from parts with documented RoHS3 Compliant status, such as the Eaton S500 series, SCHURTER 0034.1517, or Littelfuse 217 and 235 series parts.

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