5TT 250 Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The 5TT 250 is a 250 mA, 250 V AC/DC slow-blow glass cartridge fuse in 5mm x 20mm form factor manufactured by Bel Fuse Inc. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing system maintenance and new design implementations. The fuse requires a compatible holder for installation and is designed for general-purpose circuit protection applications requiring slow-blow response characteristics.

Key Parameters

Parameter	Value
Current Rating	250 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	100 A

Substitute Part Grouping Explanation

Substitution eligibility for the 5TT 250 is determined by strict equivalence across the following critical parameters:

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

All substitute parts listed meet these core electrical and mechanical requirements. Variations in secondary parameters such as breaking capacity, melting I²t, DC cold resistance, and approval agencies are documented to support engineering selection based on specific application requirements.

Parameter Comparison

Parameter	5TT 250	5TT 250-R	5ST 250-R	0218.250HXP
Manufacturer	Bel Fuse Inc.	Bel Fuse Inc.	Bel Fuse Inc.	Littelfuse Inc.
Current Rating (Amps)	250 mA	250 mA	250 mA	250 mA
Voltage Rating - AC	250 V	250 V	250 V	250 V
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Package / Case	5mm x 20mm	5mm x 20mm	5mm x 20mm	5mm x 20mm
Response Time	Slow Blow	Slow Blow	Slow Blow	Slow Blow
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C
Breaking Capacity @ Rated Voltage	100 A	100 A	35 A	35 A
Melting I²t	0.72	0.719	0.26	0.5405
DC Cold Resistance (Ohms)	3.2	3.16	1.9	1.0495
Product Status	Obsolete	Active	Active	Active
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Approval Agency	CE, CSA, UL	CE, CSA, cULus	CCC, CE, CSA, cURus, IMQ, SEMKO, VDE	CCC, CE, CSA, K-MARK, SEMKO, UL, VDE

Engineering Selection Recommendations

5TT 250-R (Direct Equivalent): This part is the active production equivalent of the obsolete 5TT 250. It maintains identical electrical specifications and mechanical form factor. The 5TT 250-R is ROHS3 compliant and carries expanded certification (cULus). This is the primary substitute for direct replacement applications.

5ST 250-R (Parametric Equivalent): This Bel Fuse Inc. part meets all core electrical and mechanical requirements. It differs in breaking capacity (35 A versus 100 A) and melting I²t (0.26 versus 0.72). The 5ST 250-R carries the broadest approval agency coverage, including CCC, IMQ, and SEMKO certifications. Selection of this part requires confirmation that the reduced breaking capacity is acceptable for the target application.

0218.250HXP (Cross-Manufacturer Equivalent): This Littelfuse Inc. part is electrically and mechanically equivalent with minor dimensional tolerance variation (5.20mm diameter versus 5.10mm). It features the lowest DC cold resistance (1.0495 Ohms) and intermediate melting I²t (0.5405). The 0218.250HXP carries comprehensive international certifications including K-MARK and VDE. Physical fit verification in existing holder assemblies is required due to diameter tolerance.

All substitute parts are ROHS3 compliant and REACH unaffected, supporting modern regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can the 5TT 250-R be used as a direct replacement for the obsolete 5TT 250?

A: Yes. The 5TT 250-R is the active production equivalent with identical current rating (250 mA), voltage rating (250 V), fuse type (cartridge glass), package dimensions (5mm x 20mm), and response time (slow blow). Both parts require the same holder assembly.

Q: What is the difference between the 5TT 250-R and 5ST 250-R?

A: Both are Bel Fuse Inc. products with identical electrical ratings and mechanical form factors. The primary difference is breaking capacity: 5TT 250-R provides 100 A breaking capacity, while 5ST 250-R provides 35 A. The 5ST 250-R also has lower melting I²t (0.26 versus 0.719) and lower DC cold resistance (1.9 versus 3.16 Ohms). Selection depends on application-specific breaking capacity requirements.

Q: Is the Littelfuse 0218.250HXP physically compatible with existing 5TT 250 holder assemblies?

A: The 0218.250HXP has a diameter of 5.20mm compared to the 5TT 250 specification of 5.10mm. Physical fit verification in the specific holder assembly is required before implementation. Length (20mm) and all electrical specifications are equivalent.

Q: What are the compliance differences between substitute parts?

A: The 5TT 250 is RoHS non-compliant. All substitute parts (5TT 250-R, 5ST 250-R, and 0218.250HXP) are ROHS3 compliant. The 5ST 250-R and 0218.250HXP carry the broadest approval agency coverage, including CCC and K-MARK certifications in addition to CE, CSA, and UL/cULus.

Q: Which substitute part should be selected for new designs?

A: The 5TT 250-R is recommended for new designs requiring direct electrical and mechanical equivalence to the original 5TT 250. For applications where breaking capacity can be reduced to 35 A, the 5ST 250-R offers expanded international certifications. The 0218.250HXP provides cross-manufacturer sourcing flexibility with equivalent electrical performance.

Q: Are all substitute parts available in the same packaging options?

A: The 5TT 250 was available in standard packaging. The 5TT 250-R, 5ST 250-R, and 0218.250HXP are all available in bulk packaging, supporting production volume requirements.

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