Littelfuse 0239.300H Glass Cartridge Fuse 300mA 250VAC 5x20mm Equivalent & Substitute Parts

Part Overview

The Littelfuse 0239.300H is a 300mA 250VAC glass cartridge fuse in 5x20mm form factor, classified as obsolete. This fuse requires a holder for installation and is designed for slow-blow response characteristics. Due to its obsolete status, equivalent and substitute parts from active manufacturers are necessary for ongoing system maintenance and new designs. The substitute parts listed maintain the core electrical and mechanical specifications while offering improved availability and compliance status.

Key Parameters

Parameter	Value
Current Rating	300 mA
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Slow Blow
Mounting Type	Requires Holder
Operating Temperature Range	-55°C to 125°C
Breaking Capacity @ Rated Voltage	35A (main part); 100A (some substitutes)

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence in the following parameters:

Current Rating: 300 mA (exact match required)
Voltage Rating (AC): 250 V (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Response Time: Slow Blow (exact match required)
Mounting Type: Requires Holder (exact match required)

All substitute parts listed meet these criteria. Variations in breaking capacity, melting I²t, DC cold resistance, and approval agencies do not disqualify substitution but may influence selection based on application requirements and regulatory compliance needs.

Parameter Comparison

Part Number	Manufacturer	Current Rating	Voltage (AC)	Package	Response Time	Breaking Capacity @ Rated Voltage	Melting I²t	DC Cold Resistance (Ohms)	Product Status	RoHS Status
0239.300H	Littelfuse Inc.	300 mA	250 V	5x20mm	Slow Blow	35A	0.63	2.25	Obsolete	Non-compliant
0239.300HXP	Littelfuse Inc.	300 mA	250 V	5x20mm	Slow Blow	35A	0.615	2.3	Active	ROHS3 Compliant
0239.300MXP	Littelfuse Inc.	300 mA	250 V	5x20mm	Slow Blow	35A	0.615	2.3	Active	ROHS3 Compliant
0239.300TXP	Littelfuse	300 mA	250 V	5x20mm	Slow Blow	35A	0.615	2.3	Active	ROHS3 Compliant
0239.300VXP	Littelfuse Inc.	300 mA	250 V	5x20mm	Slow Blow	35A	0.615	2.3	Active	ROHS3 Compliant
5TT 300-R	Bel Fuse Inc.	300 mA	250 V	5x20mm	Slow Blow	100A	0.885	2.14	Active	ROHS3 Compliant
BK/GMD-300-R	Eaton - Electronics Division	300 mA	250 V	5x20mm	Slow Blow	35A	0.65	3.215	Active	ROHS3 Compliant
BK1/GMD-300-R	Eaton - Electronics Division	300 mA	250 V	5x20mm	Slow Blow	35A	0.65	3.215	Active	ROHS3 Compliant
TSC-300MA	OptiFuse	300 mA	250 V	5x20mm	Slow Blow	100A	0.4817	Not specified	Active	ROHS3 Compliant

Engineering Selection Recommendations

All listed substitute parts are electrically and mechanically equivalent to the 0239.300H. Selection should prioritize active product status and regulatory compliance:

Littelfuse 0239.300HXP, 0239.300MXP, 0239.300TXP, and 0239.300VXP are direct Littelfuse alternatives with active status and ROHS3 compliance. These parts maintain the same breaking capacity (35A) as the original 0239.300H.

Bel Fuse 5TT 300-R and OptiFuse TSC-300MA offer higher breaking capacity (100A) with active status and ROHS3 compliance. These are suitable for applications requiring enhanced fault protection.

Eaton BK/GMD-300-R and BK1/GMD-300-R provide equivalent specifications with active status and ROHS3 compliance. Note that DC cold resistance is higher (3.215 Ohms) compared to the original part.

All substitute parts carry appropriate regulatory approvals (CE, CSA, UL, or cULus) suitable for industrial and consumer applications.

Frequently Asked Questions (FAQ)

Q: Can I directly replace 0239.300H with any of these substitute parts?

A: Yes. All listed parts are electrically and mechanically equivalent. They share identical current rating (300mA), voltage rating (250V AC), package dimensions (5x20mm), fuse type (cartridge glass), and response time (slow blow). Physical installation in the same holder is compatible.

Q: What is the difference between Littelfuse substitutes (0239.300HXP, 0239.300MXP, 0239.300TXP, 0239.300VXP)?

A: These parts are parametrically equivalent with identical electrical specifications. Differences exist in melting I²t (0.615 vs 0.63) and DC cold resistance (2.3 vs 2.25 Ohms), which are within acceptable tolerance ranges. Selection may depend on packaging availability and inventory.

Q: Why do some substitutes have higher breaking capacity (100A vs 35A)?

A: Breaking capacity indicates the maximum fault current the fuse can safely interrupt. Higher breaking capacity (5TT 300-R at 100A, TSC-300MA at 100A) provides enhanced protection in circuits with higher available fault currents. This does not affect normal operation at 300mA rated current.

Q: Are all substitutes RoHS compliant?

A: Yes. All active substitute parts listed are ROHS3 compliant. The original 0239.300H is RoHS non-compliant, making the substitutes necessary for applications requiring RoHS compliance.

Q: What certifications should I verify for my application?

A: Littelfuse substitutes carry CE, CSA, KC, and UL approvals. Bel Fuse 5TT 300-R carries CE, CSA, and cULus approvals. Eaton GMD series carry CSA and UL approvals. OptiFuse TSC-300MA carries cULus and UL 248 approvals. Verify that the selected part's certifications match your application requirements.

Q: Can I use these substitutes in new designs?

A: Yes. All substitute parts have active product status, making them suitable for new designs. Littelfuse 0239.300HXP, 0239.300MXP, 0239.300TXP, and 0239.300VXP are recommended for designs requiring Littelfuse components. Alternative manufacturers (Bel Fuse, Eaton, OptiFuse) are suitable when multi-source qualification is required.

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