3SB 2.5 Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The 3SB 2.5 is a 2.5 A, 250 V AC/DC glass cartridge fuse manufactured by Bel Fuse Inc. with slow-blow response characteristics. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts that maintain electrical and mechanical compatibility. The fuse requires a 3AB or 3AG holder and is designed for applications requiring overcurrent protection in industrial and commercial equipment.

Key Parameters

Parameter	Value
Current Rating	2.5 A
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Fuse Type	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4"
Size / Dimension	0.250" Dia x 1.252" L (6.35mm x 31.80mm)
Breaking Capacity @ Rated Voltage	100 A
Operating Temperature Range	-55°C ~ 125°C
Mounting Type	Requires Holder

Substitute Part Grouping Explanation

Substitution of the 3SB 2.5 is determined by strict equivalence across the following parameters:

Current Rating: 2.5 A (exact match required)
Voltage Rating: 250 V AC (exact match required)
Response Time: Slow Blow (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (exact match required)
Operating Temperature Range: -55°C ~ 125°C (exact match required)

All identified substitute parts meet these core electrical and mechanical parameters. Variations in breaking capacity, melting I²t, DC cold resistance, and approval agencies do not preclude substitution when the above parameters are identical.

Parameter Comparison

Parameter	3SB 2.5	3SB 2.5-R	031302.5HXP	031302.5MXP	031302.5VXP	TSA-2.5A
Manufacturer	Bel Fuse Inc.	Bel Fuse Inc.	Littelfuse Inc.	Littelfuse Inc.	Littelfuse Inc.	OptiFuse
Current Rating (Amps)	2.5 A	2.5 A	2.5 A	2.5 A	2.5 A	2.5 A
Voltage Rating - AC	250 V	250 V	250 V	250 V	250 V	250 V
Response Time	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"	3AB, 3AG, 1/4" x 1-1/4"
Size / Dimension	0.250" Dia x 1.252" L (6.35mm x 31.80mm)	0.250" Dia x 1.252" L (6.35mm x 31.80mm)	0.250" Dia x 1.250" L (6.35mm x 31.75mm)	0.250" Dia x 1.250" L (6.35mm x 31.75mm)	0.250" Dia x 1.250" L (6.35mm x 31.75mm)	0.250" Dia x 1.252" L (6.35mm x 31.80mm)
Breaking Capacity @ Rated Voltage	100 A	200 A	100 A	100 A	100 A	100 A
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Product Status	Obsolete	Active	Active	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

The 3SB 2.5 is obsolete and should be replaced with an active equivalent. All substitute parts listed maintain identical electrical and mechanical specifications required for direct substitution.

3SB 2.5-R (Bel Fuse Inc.): Direct manufacturer replacement from Bel Fuse Inc. with active product status. Offers higher breaking capacity (200 A vs. 100 A) and improved RoHS3 compliance. Recommended for applications requiring continued Bel Fuse sourcing.

031302.5HXP, 031302.5MXP, 031302.5VXP (Littelfuse Inc.): All three Littelfuse variants meet core substitution parameters. 031302.5MXP offers highest inventory availability (9,244 pcs). All variants are RoHS3 compliant with active product status. Littelfuse variants include K-MARK certification (031302.5HXP and 031302.5MXP) or KC certification (031302.5VXP).

TSA-2.5A (OptiFuse): Active product with RoHS3 compliance and cULus/UL 248 certification. Suitable for applications where OptiFuse sourcing is preferred.

Frequently Asked Questions (FAQ)

Q: Can the 3SB 2.5 be directly replaced with any of the listed substitutes?

A: Yes. All substitute parts maintain identical current rating (2.5 A), voltage rating (250 V AC), response time (slow blow), fuse type (cartridge, glass), package designation (3AB, 3AG, 1/4" x 1-1/4"), and operating temperature range (-55°C ~ 125°C). Physical dimensions are equivalent within manufacturing tolerance.

Q: What is the difference between the Littelfuse variants (031302.5HXP, 031302.5MXP, 031302.5VXP)?

A: All three Littelfuse variants are electrically and mechanically identical. Differences exist only in approval agency certifications: 031302.5HXP and 031302.5MXP include K-MARK certification, while 031302.5VXP includes KC certification. Selection should be based on regional regulatory requirements and inventory availability.

Q: Does the higher breaking capacity of 3SB 2.5-R (200 A vs. 100 A) affect compatibility?

A: No. Higher breaking capacity does not affect substitution compatibility. The 3SB 2.5-R maintains all other electrical and mechanical parameters identical to the original 3SB 2.5 and can be used as a direct replacement.

Q: Are there RoHS compliance considerations for substitution?

A: The original 3SB 2.5 is RoHS non-compliant. All active substitutes (3SB 2.5-R, Littelfuse variants, and TSA-2.5A) are RoHS3 compliant, making them suitable for applications with RoHS requirements.

Q: Which substitute offers the best inventory availability?

A: 031302.5MXP (Littelfuse Inc.) offers the highest inventory with 9,244 pcs in stock, followed by 3SB 2.5-R (Bel Fuse Inc.) with 2,344 pcs.

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