5ST 8 Glass Cartridge Fuse - Equivalent & Substitute Parts

Part Overview

The 5ST 8 is an 8A, 250V AC/DC slow-blow glass cartridge fuse manufactured by Bel Fuse Inc. in a 5mm x 20mm form factor. This part is classified as obsolete, though it remains in stock with 797 units available. Due to its obsolete status, identifying active equivalent and substitute parts is essential for ongoing system maintenance and new design implementations. Substitute parts maintain identical electrical ratings and mechanical dimensions while offering improved availability and compliance with current regulatory standards.

Key Parameters

Parameter	Value
Current Rating	8 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Package / Case	5mm x 20mm
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	80A
Operating Temperature Range	-55°C to 125°C
RoHS Status	RoHS non-compliant (main part); ROHS3 compliant (substitutes)

Substitute Part Grouping Explanation

Substitution for the 5ST 8 is determined by strict equivalence across the following critical parameters:

Current Rating: 8 A (exact match required)
Voltage Rating: 250 V AC (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 identified substitutes meet these criteria. Secondary parameters including Breaking Capacity, Melting I²t, DC Cold Resistance, and approval certifications vary within acceptable ranges for the 5mm x 20mm slow-blow cartridge fuse category. These variations reflect different manufacturing standards and regional compliance requirements but do not affect functional interchangeability in applications designed for the 5ST 8 specification.

Parameter Comparison

Part Number	Manufacturer	Current (A)	Voltage (V AC)	Package	Response Time	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status
5ST 8	Bel Fuse Inc.	8	250	5mm x 20mm	Slow Blow	80	260	0.006	Obsolete	Non-compliant
5ST 8-R	Bel Fuse Inc.	8	250	5mm x 20mm	Slow Blow	80	260	0.006	Active	ROHS3 Compliant
5ET 8-R	Bel Fuse Inc.	8	250	5mm x 20mm	Slow Blow	150	252	0.007	Active	ROHS3 Compliant
0034.3126	SCHURTER Inc.	8	250	5mm x 20mm	Slow Blow	80	275	—	Active	ROHS3 Compliant
0218008.MXP	Littelfuse Inc.	8	250	5mm x 20mm	Slow Blow	80	341.5	0.0059	Active	ROHS3 Compliant
0218008.HXP	Littelfuse Inc.	8	250	5mm x 20mm	Slow Blow	80	341.5	0.0059	Active	ROHS3 Compliant
0218008.TXP	Littelfuse Inc.	8	250	5mm x 20mm	Slow Blow	80	341.5	0.0059	Active	ROHS3 Compliant
0218008.VXP	Littelfuse Inc.	8	250	5mm x 20mm	Slow Blow	80	341.5	0.0059	Active	ROHS3 Compliant

Engineering Selection Recommendations

Direct Replacement Priority:

5ST 8-R (Bel Fuse Inc.) is the primary direct substitute. It maintains identical electrical and mechanical specifications to the 5ST 8 while offering active product status and ROHS3 compliance. This part is recommended for applications requiring minimal design validation.

Alternative Manufacturers:

0218008.MXP, 0218008.HXP, 0218008.TXP, and 0218008.VXP (Littelfuse Inc. Series 218) provide functionally equivalent performance with broader international certification coverage (CE, CSA, K-MARK, PSE, UL, VDE). These parts are suitable for designs requiring multi-regional compliance documentation.

0034.3126 (SCHURTER Inc. FST 5x20 series) offers equivalent performance with certifications including CQC, cURus, PSE/JET, and VDE, making it suitable for applications with specific regional requirements.

Higher Breaking Capacity Option:

5ET 8-R (Bel Fuse Inc.) provides a higher breaking capacity of 150A compared to the standard 80A, with marginally lower melting I²t (252 vs. 260). This part is suitable for applications requiring enhanced fault protection while maintaining identical current and voltage ratings.

All substitute parts are active products with current manufacturing support and improved regulatory compliance compared to the obsolete 5ST 8.

Frequently Asked Questions (FAQ)

Q: Can I use 5ST 8-R as a direct replacement for 5ST 8?

A: Yes. The 5ST 8-R maintains identical electrical ratings (8A, 250V AC), response time (slow blow), and mechanical dimensions (5mm x 20mm). The primary difference is product status (active vs. obsolete) and RoHS compliance. No circuit modifications are required.

Q: What is the difference between the Bel Fuse and Littelfuse substitutes?

A: All maintain identical current, voltage, and package specifications. Littelfuse parts (0218008 series) feature higher melting I²t values (341.5 vs. 260) and broader international certifications. Bel Fuse parts offer direct lineage to the original 5ST 8 design. Selection depends on certification requirements and supply chain preferences.

Q: Why does 5ET 8-R have a higher breaking capacity?

A: The 5ET 8-R is from a different Bel Fuse series (5ET vs. 5ST) with enhanced fault protection capability (150A vs. 80A breaking capacity). It remains functionally equivalent for the 8A, 250V application but provides additional margin in high-fault-current environments. Melting I²t is slightly lower (252 vs. 260), reflecting the different thermal design.

Q: Are all substitutes RoHS3 compliant?

A: All identified substitutes are ROHS3 compliant. The original 5ST 8 is RoHS non-compliant. If RoHS compliance is a design requirement, any substitute part satisfies this criterion.

Q: Does package size vary among substitutes?

A: All substitutes maintain the 5mm x 20mm form factor. Minor dimensional variations exist (e.g., 0034.3126 at 5.20mm diameter vs. 5.10mm for others), but these fall within standard mechanical tolerances for 5x20 cartridge fuse holders and do not affect interchangeability.

Q: Which substitute has the broadest certification coverage?

A: Littelfuse 0218008 series parts (MXP, HXP, TXP, VXP) carry the most comprehensive certification set: CE, CSA, K-MARK, PSE, UL, VDE. These are recommended for applications requiring multi-regional compliance documentation.

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