Littelfuse 02171.25H Glass Cartridge Fuse 1.25A 250VAC 5x20mm Equivalent & Substitute Parts

Part Overview

The Littelfuse 02171.25H is a 1.25A 250VAC fast-blow glass cartridge fuse in 5x20mm form factor, designed for circuit protection in AC/DC applications. This part is classified as obsolete. Equivalent and substitute parts are available from Littelfuse's active product lines, offering improved availability and compliance status while maintaining electrical and mechanical compatibility.

Key Parameters

Parameter	Value
Current Rating	1.25 A
Voltage Rating (AC)	250 V
Response Time	Fast Blow
Package / Case	5mm x 20mm
Fuse Type	Cartridge, Glass
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	35A
Melting I²t	2.23
Operating Temperature Range	-55°C ~ 125°C
Size / Dimension	0.205" Dia x 0.787" L (5.20mm x 20.00mm)

Substitute Part Grouping Explanation

Substitution for the 02171.25H is determined by strict equivalence across the following electrical and mechanical parameters:

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

Substitute parts are grouped into two categories:

Category 1: Series 217 Littelfuse Parts (Direct Electrical Equivalents) Parts 02171.25HXP, 02171.25MXBP, 02171.25MXP, 02171.25TXP, and 02171.25VXP maintain identical electrical characteristics (Breaking Capacity 35A, Melting I²t 2.23) and are active products with improved RoHS3 compliance.

Category 2: Series 235 Littelfuse Parts (Enhanced Breaking Capacity) Parts 02351.25HXP, 02351.25MXP, and 02351.25VXP share all core electrical and mechanical parameters but feature increased Breaking Capacity (100A) and reduced Melting I²t (1.085), suitable for applications requiring higher fault current protection.

Category 3: Series 617 Littelfuse Parts (Alternative Certification) Part 06171.25MXP maintains identical electrical characteristics with alternative approval agency certifications (CCC, CE, CSA, UR, VDE).

Category 4: Eaton Alternative Part BK/GDB-1.25A from Eaton Electronics Division provides cross-manufacturer equivalence with identical electrical and mechanical parameters.

Parameter Comparison

Part Number	Manufacturer	Series	Current (A)	Voltage (V AC)	Response	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status
02171.25H	Littelfuse Inc.	217	1.25	250	Fast Blow	5x20mm	35	2.23	0.07	Obsolete	RoHS non-compliant
02171.25HXP	Littelfuse Inc.	217	1.25	250	Fast Blow	5x20mm	35	2.23	0.0701	Active	ROHS3 Compliant
02171.25MXBP	Littelfuse Inc.	217	1.25	250	Fast Blow	5x20mm	35	2.23	0.0701	Active	ROHS3 Compliant
02171.25MXP	Littelfuse Inc.	217	1.25	250	Fast Blow	5x20mm	35	2.23	0.0701	Active	ROHS3 Compliant
02171.25TXP	Littelfuse	217	1.25	250	Fast Blow	5x20mm	35	2.23	0.0701	Active	ROHS3 Compliant
02171.25VXP	Littelfuse Inc.	217	1.25	250	Fast Blow	5x20mm	35	2.23	0.0701	Active	ROHS3 Compliant
02351.25HXP	Littelfuse Inc.	235	1.25	250	Fast Blow	5x20mm	100	1.085	0.1055	Active	ROHS3 Compliant
02351.25MXP	Littelfuse Inc.	235	1.25	250	Fast Blow	5x20mm	100	1.085	0.1055	Active	ROHS3 Compliant
02351.25VXP	Littelfuse Inc.	235	1.25	250	Fast Blow	5x20mm	100	1.085	0.1055	Active	ROHS3 Compliant
06171.25MXP	Littelfuse Inc.	617	1.25	250	Fast Blow	5x20mm	35	2.23	0.0701	Active	ROHS3 Compliant
BK/GDB-1.25A	Eaton - Electronics Division	GDB	1.25	250	Fast Blow	5x20mm	35	0.84	0.096	Active	RoHS Compliant

Engineering Selection Recommendations

Primary Recommendation: Series 217 Active Parts (02171.25HXP, 02171.25MXBP, 02171.25MXP, 02171.25TXP, 02171.25VXP)

These parts provide direct electrical and mechanical equivalence to the obsolete 02171.25H with active product status and ROHS3 compliance. All maintain identical breaking capacity (35A) and melting I²t (2.23). Selection among these variants is based on packaging preference and inventory availability. Approval agencies include BSI, CE, CCC, CSA, KC, PSE, SEMKO, UR, and VDE.

Secondary Recommendation: Series 235 Parts (02351.25HXP, 02351.25MXP, 02351.25VXP)

These parts are suitable for applications requiring enhanced fault current protection, with breaking capacity increased to 100A. Melting I²t is reduced to 1.085, resulting in faster response to higher fault currents. Approval agencies include CE, CSA, KC, PSE, and UL. Use only when circuit design accommodates the different thermal response characteristic.

Alternative Recommendation: Series 617 Part (06171.25MXP)

Part 06171.25MXP maintains identical electrical characteristics to Series 217 parts with alternative certification coverage (CCC, CE, CSA, UR, VDE). Suitable for applications requiring specific regional compliance certifications.

Cross-Manufacturer Option: Eaton BK/GDB-1.25A

This part provides electrical and mechanical equivalence from an alternative manufacturer. Melting I²t differs (0.84 vs. 2.23), indicating faster thermal response. Approved by UL and VDE. Use only when cross-manufacturer sourcing is required and circuit design accommodates the different thermal characteristic.

Frequently Asked Questions (FAQ)

Q: Can I directly replace the obsolete 02171.25H with any of the recommended substitutes?

A: Yes. All recommended Series 217 parts (02171.25HXP, 02171.25MXBP, 02171.25MXP, 02171.25TXP, 02171.25VXP) are direct replacements. They maintain identical current rating (1.25A), voltage rating (250V AC), response time (Fast Blow), package (5x20mm), and breaking capacity (35A). The primary difference is product status (active vs. obsolete) and RoHS compliance.

Q: What is the difference between Series 217 and Series 235 parts?

A: Series 235 parts feature increased breaking capacity (100A vs. 35A) and reduced melting I²t (1.085 vs. 2.23). This results in faster thermal response to higher fault currents. Use Series 235 only if your circuit design requires this enhanced protection characteristic.

Q: Are the packaging variants (HXP, MXBP, MXP, TXP, VXP) electrically interchangeable?

A: Yes. All Series 217 variants maintain identical electrical specifications. Packaging designations indicate different distribution formats (bulk, tape, tray). Selection is based on procurement and assembly requirements, not electrical performance.

Q: Can I use the Eaton BK/GDB-1.25A as a substitute?

A: The Eaton part is mechanically and electrically compatible for the core parameters (1.25A, 250V, 5x20mm, Fast Blow). However, its melting I²t (0.84) differs significantly from the Littelfuse 02171.25H (2.23), resulting in faster thermal response. Use only if your circuit design accommodates this difference and cross-manufacturer sourcing is required.

Q: What certifications should I verify for my application?

A: Verify that the selected substitute part includes all certifications required by your application and regional standards. Series 217 parts include BSI, CE, CCC, CSA, KC, PSE, SEMKO, UR, and VDE. Series 235 parts include CE, CSA, KC, PSE, and UL. The Eaton part includes UL and VDE. Confirm compliance with your specific regulatory requirements.

Q: Is the 02171.25H still available?

A: The 02171.25H is classified as obsolete. Active equivalent parts are available from Littelfuse's Series 217, 235, and 617 product lines with improved availability and compliance status.

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