Bel Fuse Inc. 5ST 2 Glass Cartridge Fuse - Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 5ST 2 is a 2 A, 250 V AC/DC glass cartridge fuse with slow-blow response characteristics, designed for 5mm x 20mm holder-based applications. This part is classified as obsolete, making identification of active equivalent and substitute components essential for ongoing system support and new design implementations. The 5ST 2 requires a dedicated fuse holder for installation and operates across a temperature range of -55°C to 125°C with a breaking capacity of 35 A at rated voltage.

Key Parameters

Parameter	Value
Current Rating	2 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Slow Blow
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	35 A
Operating Temperature Range	-55°C to 125°C
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution for the 5ST 2 is determined by strict equivalence across the following parameters: current rating (2 A), voltage rating (250 V AC), fuse type (cartridge glass), package dimensions (5mm x 20mm), response time (slow blow), and mounting configuration (holder-based). Parts are categorized into three groups:

Direct Manufacturer Equivalents maintain identical electrical and mechanical specifications with active product status, ensuring drop-in compatibility. These include the 5ST 2-R (Bel Fuse Inc., same series, active status), 0218002.MXBP, 0218002.MXP, and 0218002.VXP (Littelfuse Inc., 218 series), and 0034.3120 (SCHURTER Inc., FST 5x20 series).

Parametric Equivalents share core electrical parameters (2 A, 250 V, slow blow, 5mm x 20mm) but differ in breaking capacity or melting I²t characteristics. These include 5ET 2-R (150 A breaking capacity, 92 melting I²t), 5TT 2-R (100 A breaking capacity, 29.9 melting I²t), and 0034.3779 (SCHURTER Inc., FSL 5x20 series, 100 A breaking capacity, 4.45 melting I²t).

Mounting Variant includes 5STP 2-R (Bel Fuse Inc., 5STP series), which maintains all electrical specifications but uses through-hole mounting instead of holder-based installation, with slightly larger physical dimensions (5.50mm x 21.00mm).

Parameter Comparison

Part Number	Manufacturer	Series	Current (A)	Voltage (V AC)	Response	Package	Breaking Capacity (A)	Melting I²t	Mounting Type	Product Status	RoHS Status
5ST 2	Bel Fuse Inc.	5ST	2	250	Slow Blow	5x20mm	35	12	Requires Holder	Obsolete	Non-compliant
5ST 2-R	Bel Fuse Inc.	5ST	2	250	Slow Blow	5x20mm	35	12	Requires Holder	Active	ROHS3 Compliant
5STP 2-R	Bel Fuse Inc.	5STP	2	250	Slow Blow	5x20mm (Axial)	35	12	Through Hole	Active	ROHS3 Compliant
5ET 2-R	Bel Fuse Inc.	5ET	2	250	Slow Blow	5x20mm	150	92	Requires Holder	Active	ROHS3 Compliant
5TT 2-R	Bel Fuse Inc.	5TT	2	250	Slow Blow	5x20mm	100	29.9	Requires Holder	Active	ROHS3 Compliant
0034.3120	SCHURTER Inc.	FST 5x20	2	250	Slow Blow	5x20mm	35	16	Requires Holder	Active	ROHS3 Compliant
0218002.MXBP	Littelfuse Inc.	218	2	250	Slow Blow	5x20mm	35	14.45	Requires Holder	Active	ROHS3 Compliant
0218002.MXP	Littelfuse Inc.	218	2	250	Slow Blow	5x20mm	35	14.45	Requires Holder	Active	ROHS3 Compliant
0218002.VXP	Littelfuse Inc.	218	2	250	Slow Blow	5x20mm	35	14.45	Requires Holder	Active	ROHS3 Compliant
0034.3779	SCHURTER Inc.	FSL 5x20	2	250	Slow Blow	5x20mm	100	4.45	Requires Holder	Active	ROHS3 Compliant
0213002.MXP	Littelfuse Inc.	213	2	250	Slow Blow	5x20mm	35	92.705	Requires Holder	Active	ROHS3 Compliant

Engineering Selection Recommendations

For direct replacement of the obsolete 5ST 2 in existing designs, the 5ST 2-R from Bel Fuse Inc. is the primary choice, offering identical electrical and mechanical specifications with active product status and ROHS3 compliance. This part maintains the same series designation, breaking capacity (35 A), and melting I²t (12), ensuring functional equivalence.

When cross-manufacturer substitution is required, the Littelfuse 218 series parts (0218002.MXBP, 0218002.MXP, 0218002.VXP) provide direct electrical equivalence with 35 A breaking capacity and 14.45 melting I²t. The SCHURTER 0034.3120 (FST 5x20 series) also qualifies as a direct substitute with matching 35 A breaking capacity and 16 melting I²t.

For applications requiring higher breaking capacity, the 5ET 2-R (150 A) and 5TT 2-R (100 A) from Bel Fuse Inc., as well as the SCHURTER 0034.3779 (100 A), are parametric equivalents that maintain the 2 A current rating and 250 V voltage rating. These parts differ in melting I²t and breaking capacity characteristics and should be selected based on specific circuit protection requirements.

The 5STP 2-R represents a mounting variant for applications requiring through-hole installation instead of holder-based mounting. Physical dimensions increase slightly to 5.50mm x 21.00mm, and this part maintains identical electrical specifications.

All recommended substitutes carry active product status and ROHS3 compliance, supporting long-term supply chain continuity and regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can the 5ST 2-R be used as a direct replacement for the obsolete 5ST 2?

A: Yes. The 5ST 2-R maintains identical electrical specifications (2 A, 250 V, slow blow), mechanical dimensions (5mm x 20mm), breaking capacity (35 A), and melting I²t (12). Both require holder-based mounting. The primary difference is product status: 5ST 2-R is active with ROHS3 compliance.

Q: What is the difference between direct equivalents and parametric equivalents?

A: Direct equivalents (5ST 2-R, 0218002.MXBP, 0218002.MXP, 0218002.VXP, 0034.3120) share identical breaking capacity (35 A) and melting I²t values. Parametric equivalents (5ET 2-R, 5TT 2-R, 0034.3779) maintain the 2 A current rating and 250 V voltage rating but feature higher breaking capacities (100-150 A) and different melting I²t characteristics. Selection depends on circuit protection requirements.

Q: Can I use the 5STP 2-R as a substitute for the 5ST 2?

A: The 5STP 2-R is electrically equivalent but uses through-hole mounting instead of holder-based installation. Physical dimensions are slightly larger (5.50mm x 21.00mm versus 5.10mm x 20.00mm). Use this part only if your application supports through-hole mounting.

Q: Are all substitute parts ROHS3 compliant?

A: All recommended active substitutes carry ROHS3 compliance. The original 5ST 2 is marked as RoHS non-compliant due to its obsolete status.

Q: What certifications should I verify when selecting a substitute?

A: The original 5ST 2 carries CE, CSA, IMQ, SEMKO, UL, and VDE approvals. Direct equivalents maintain comparable certification coverage. Verify that your selected substitute carries certifications required by your application and regional standards.

Q: How do melting I²t values affect fuse selection?

A: Melting I²t indicates the thermal energy required to melt the fuse element. The 5ST 2 has a melting I²t of 12. Direct equivalents maintain similar values (12-16). Parametric equivalents with higher melting I²t values (29.9-92.705) provide different thermal response characteristics and should be selected based on specific circuit protection requirements.

Q: What is the operating temperature range for substitute parts?

A: Most substitute parts operate across -55°C to 125°C, matching the original 5ST 2. The SCHURTER 0034.3779 operates across a narrower range (-40°C to 85°C) and should be verified for temperature-critical applications.

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