Littelfuse 031302.5H Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 031302.5H is a 2.5 A, 250 V AC/DC slow-blow glass cartridge fuse in the 3AB/3AG package format (1/4" x 1-1/4"). This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing system maintenance and new designs. The fuse requires a compatible holder for installation and is designed for circuit protection applications requiring slow-blow response characteristics.

Key Parameters

Parameter	Value
Current Rating	2.5 A
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (6.35mm x 31.75mm)
Fuse Type	Cartridge, Glass
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	100A
DC Cold Resistance	0.0805 Ohms
Melting I²t	130

Substitute Part Grouping Explanation

Substitution for the 031302.5H is determined by strict equivalence across the following parameters: current rating (2.5 A), voltage rating (250 V AC), response time (slow blow), package format (3AB/3AG, 1/4" x 1-1/4"), and fuse type (cartridge, glass). All substitute parts listed maintain these core electrical and mechanical specifications.

Substitute parts are grouped into two categories:

Direct Manufacturer Equivalents (Littelfuse): Parts 031302.5HXP, 031302.5MXP, and 031302.5VXP are active-status variants from the same manufacturer with identical electrical ratings and package specifications. These parts differ primarily in packaging format (bulk) and compliance certifications.

Parametric Equivalents (Cross-Manufacturer): Parts from Eaton Electronics Division (MDL and MDQ series) and SCHURTER (0034.3421) meet the core electrical and mechanical parameters. These parts maintain the same current, voltage, response time, and physical dimensions, though breaking capacity and melting I²t values may vary within acceptable ranges for the application.

Parameter Comparison

Part Number	Manufacturer	Current (A)	Voltage (V AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Resistance (Ohms)	Product Status	RoHS Status
031302.5H	Littelfuse	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	130	0.0805	Obsolete	Non-compliant
031302.5HXP	Littelfuse	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	130	0.0811	Active	ROHS3 Compliant
031302.5MXP	Littelfuse	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	130	0.0811	Active	ROHS3 Compliant
031302.5VXP	Littelfuse	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	130	0.0811	Active	ROHS3 Compliant
0034.3421	SCHURTER	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	35	48	Not specified	Obsolete	ROHS3 Compliant
BK/MDL-2-1/2-R	Eaton	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	63.1	0.081	Active	ROHS3 Compliant
BK/MDL-2-1/2EX-R	Eaton	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	63.1	0.081	Active	RoHS Compliant
BK/MDQ-2-1/2	Eaton	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	Not specified	0.1005	Active	Non-compliant
MDL-2-1/2-R	Eaton	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	100	63.1	0.081	Active	RoHS Compliant
MDQ-2-1/2	Eaton	2.5	250	Slow Blow	3AB/3AG, 1/4" x 1-1/4"	35	Not specified	0.1005	Active	Not specified

Engineering Selection Recommendations

For applications requiring direct replacement of the obsolete 031302.5H, the Littelfuse active-status variants (031302.5HXP, 031302.5MXP, 031302.5VXP) provide the highest compatibility. These parts maintain identical electrical specifications and package dimensions while offering improved compliance status (ROHS3 Compliant) and extended operating temperature range (-55°C to 125°C).

When cross-manufacturer substitution is necessary, Eaton MDL series parts (BK/MDL-2-1/2-R, BK/MDL-2-1/2EX-R, MDL-2-1/2-R) are preferred due to matching breaking capacity (100A) and active product status. These parts are RoHS compliant and maintain equivalent DC cold resistance values.

Eaton MDQ series parts (BK/MDQ-2-1/2, MDQ-2-1/2) present a lower breaking capacity (35A) compared to the original specification (100A). Selection of MDQ variants should be limited to applications where the reduced breaking capacity is acceptable for the circuit protection requirement.

The SCHURTER 0034.3421 is obsolete and presents reduced breaking capacity (35A) and melting I²t (48) relative to the original part. This part should be considered only when no other alternatives are available and application requirements permit the reduced performance parameters.

Frequently Asked Questions (FAQ)

Q: Can I use any of these substitute parts interchangeably with the 031302.5H?

A: All listed substitute parts share the core electrical specifications (2.5 A, 250 V AC, slow-blow response) and physical package format (3AB/3AG, 1/4" x 1-1/4"). However, breaking capacity and melting I²t values differ. Verify that the substitute part's breaking capacity meets or exceeds your circuit protection requirements before selection.

Q: What is the difference between Littelfuse 031302.5HXP, 031302.5MXP, and 031302.5VXP?

A: These three parts are electrically and mechanically identical. The primary differences are packaging format (all bulk) and approval agency certifications. 031302.5HXP carries CE, CSA, K-MARK, PSE, and UL approvals. 031302.5MXP carries CE, CSA, K-MARK, PSE, and UL approvals. 031302.5VXP carries CE, CSA, KC, PSE, and UL approvals. Select based on required regulatory certifications for your application region.

Q: Why do some substitute parts have lower breaking capacity?

A: Breaking capacity indicates the maximum fault current the fuse can safely interrupt. The original 031302.5H and most Eaton MDL variants specify 100A breaking capacity. Eaton MDQ series and SCHURTER 0034.3421 specify 35A. Lower breaking capacity may be acceptable in applications with inherently limited fault current, but must be verified against circuit design requirements.

Q: Are all substitute parts RoHS compliant?

A: No. The original 031302.5H is RoHS non-compliant. Littelfuse active variants (031302.5HXP, 031302.5MXP, 031302.5VXP) are ROHS3 compliant. Eaton MDL series parts are RoHS compliant. Eaton MDQ series and SCHURTER 0034.3421 compliance status varies. Verify RoHS requirements for your application before selection.

Q: Can I use these fuses in any 3AB/3AG holder?

A: Yes. All substitute parts maintain the 3AB/3AG package format and 1/4" x 1-1/4" physical dimensions. They are mechanically compatible with any holder designed for this standard package format.

Q: What is the significance of melting I²t values?

A: Melting I²t indicates the thermal energy required to melt the fuse element. The original 031302.5H specifies 130. Eaton MDL variants specify 63.1, and SCHURTER 0034.3421 specifies 48. Lower melting I²t values result in faster response to overcurrent conditions. Verify that the substitute part's melting I²t is appropriate for your circuit protection timing requirements.

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