Littelfuse 02321.25M Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The Littelfuse 02321.25M is a 1.25 A, 250 V AC/DC glass cartridge fuse with a 5mm x 20mm form factor, designed for applications requiring medium-blow response characteristics. This part is classified as obsolete, making equivalent and substitute parts necessary for ongoing system maintenance and new designs. The fuse requires a holder for installation and operates across a temperature range of -55°C to 125°C.

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	Medium Blow
Breaking Capacity @ Rated Voltage	100 A
Mounting Type	Requires Holder
Operating Temperature Range	-55°C to 125°C

Substitute Part Grouping Explanation

Substitution for the 02321.25M is determined by strict equivalence across the following parameters: current rating (1.25 A), voltage rating (250 V AC), fuse type (cartridge glass), physical dimensions (5mm x 20mm), response time (medium blow), and breaking capacity (100 A). All substitute parts listed maintain these core electrical and mechanical specifications, ensuring functional compatibility within applications originally designed for the 02321.25M.

Substitute parts are grouped into two categories: Littelfuse parametric equivalents (02321.25MXP, 02341.25MXBP, 02341.25MXP) and cross-manufacturer alternatives (Eaton GMC series and OptiFuse MSC series). Each substitute maintains identical current, voltage, and physical specifications while differing in product status, compliance certifications, and internal electrical characteristics such as melting I²t and DC cold resistance.

Parameter Comparison

Part Number	Manufacturer	Current Rating (A)	Voltage Rating (V AC)	Package	Response Time	Breaking Capacity (A)	Product Status	RoHS Status
02321.25M	Littelfuse Inc.	1.25	250	5mm x 20mm	Medium Blow	100	Obsolete	Non-compliant
02321.25MXP	Littelfuse	1.25	250	5mm x 20mm	Medium Blow	100	Active	ROHS3 Compliant
02341.25MXBP	Littelfuse Inc.	1.25	250	5mm x 20mm	Medium Blow	100	Active	ROHS3 Compliant
02341.25MXP	Littelfuse Inc.	1.25	250	5mm x 20mm	Medium Blow	100	Active	ROHS3 Compliant
BK/GMC-1.25-R	Eaton - Electronics Division	1.25	250	5mm x 20mm	Medium Blow	100	Active	ROHS3 Compliant
BK1/GMC-1.25-R	Eaton - Electronics Division	1.25	250	5mm x 20mm	Medium Blow	100	Active	ROHS3 Compliant
GMC-1.25-R	Eaton - Electronics Division	1.25	250	5mm x 20mm	Medium Blow	100	Active	ROHS3 Compliant
MSC-1.25A	OptiFuse	1.25	250	5mm x 20mm	Medium Blow	100	Active	ROHS3 Compliant

Engineering Selection Recommendations

All substitute parts maintain electrical and mechanical equivalence to the 02321.25M. Selection among available substitutes should be based on product status and compliance requirements:

Littelfuse parametric equivalents (02321.25MXP, 02341.25MXBP, 02341.25MXP) are active products with ROHS3 compliance, providing direct manufacturer continuity. These parts are recommended for applications requiring Littelfuse-specific certifications or supply chain consistency.

Eaton GMC series alternatives (BK/GMC-1.25-R, BK1/GMC-1.25-R, GMC-1.25-R) are active products with ROHS3 compliance and certifications including CSA, KC-MARK, MITI, and UL. These parts are suitable for applications where cross-manufacturer sourcing is acceptable.

OptiFuse MSC-1.25A is an active product with ROHS3 compliance and cULus/UL 248 certifications, providing an alternative source for applications requiring OptiFuse-specific approvals.

Frequently Asked Questions (FAQ)

Q: Can I directly replace the 02321.25M with any of the listed substitutes?

A: Yes. All listed substitutes maintain identical current rating (1.25 A), voltage rating (250 V AC), physical dimensions (5mm x 20mm), response time (medium blow), and breaking capacity (100 A). Direct mechanical and electrical substitution is supported.

Q: What is the difference between Littelfuse series 232 and series 234?

A: Both series maintain the same electrical specifications for the 1.25 A, 250 V rating. The primary differences are internal characteristics such as melting I²t and DC cold resistance. Series 234 parts (02341.25MXBP, 02341.25MXP) have lower melting I²t values (3.39) compared to series 232 parts (4.22 for the obsolete 02321.25M, 4.11 for 02321.25MXP).

Q: Are there compliance differences between manufacturers?

A: Yes. The 02321.25M is RoHS non-compliant. All active substitutes are ROHS3 compliant. Certification agencies vary by manufacturer: Littelfuse parts carry CE, KC, PSE, CSA, and UL approvals; Eaton GMC series carry CSA, KC-MARK, MITI, and UL; OptiFuse MSC series carry cULus and UL 248 certifications.

Q: Does the fuse holder compatibility change between substitutes?

A: No. All substitute parts require a holder and maintain the 5mm x 20mm form factor, ensuring compatibility with existing fuse holder installations.

Q: What is the significance of melting I²t and DC cold resistance differences?

A: Melting I²t and DC cold resistance are internal electrical characteristics that affect fuse response behavior under specific fault conditions. All listed substitutes maintain the same medium-blow response classification and 100 A breaking capacity, ensuring equivalent protection performance in the specified application range.

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