Bel Fuse Inc. 5ET 2.5 Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 5ET 2.5 is a 2.5 A, 250 V AC/DC slow blow glass cartridge fuse in a 5mm x 20mm package format. This component is classified as obsolete, requiring identification of active equivalent and substitute parts for ongoing system support and procurement. The 5ET 2.5 series fuse is designed for applications requiring slow blow response characteristics with a 150 A breaking capacity at rated voltage and operates across a temperature range of -55°C to 125°C.

Key Parameters

Parameter	Value
Manufacturer Part Number	5ET 2.5
Manufacturer	Bel Fuse Inc.
Current Rating	2.5 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Slow Blow
Breaking Capacity @ Rated Voltage	150 A
Melting I²t	137
Operating Temperature Range	-55°C to 125°C
Mounting Type	Requires Holder
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitution eligibility for the 5ET 2.5 is determined by the following critical parameters: current rating (2.5 A), voltage rating (250 V AC), fuse type (cartridge glass), package dimensions (5mm x 20mm), response time (slow blow), and operating temperature range (-55°C to 125°C). Parts are classified into three substitution categories:

Direct Manufacturer Equivalents maintain identical electrical and mechanical specifications with active product status, ensuring seamless replacement without design modification.

Parametric Equivalents share all critical electrical and mechanical parameters but originate from the same manufacturer with different series designations. These parts are functionally interchangeable within the specified parameter envelope.

Similar Manufacturer Parts originate from alternative manufacturers (Littelfuse, Eaton) and maintain equivalent current, voltage, package, and response time specifications. Dimensional tolerances and DC cold resistance values may vary within acceptable engineering margins. These parts require verification of holder compatibility and certification requirements for the target application.

Parameter Comparison

Part Number	Manufacturer	Current Rating (A)	Voltage (V AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status
5ET 2.5	Bel Fuse Inc.	2.5	250	Slow Blow	5mm x 20mm	150	137	0.031	Obsolete	Non-compliant
5ET 2.5-R	Bel Fuse Inc.	2.5	250	Slow Blow	5mm x 20mm	150	137	0.031	Active	RoHS3 Compliant
5ST 2.5-R	Bel Fuse Inc.	2.5	250	Slow Blow	5mm x 20mm	35	20	0.02	Active	RoHS3 Compliant
5TT 2.5-R	Bel Fuse Inc.	2.5	250	Slow Blow	5mm x 20mm	100	45	0.056	Active	RoHS3 Compliant
021802.5HXP	Littelfuse	2.5	250	Slow Blow	5mm x 20mm	35	23.25	0.0219	Active	RoHS3 Compliant
021802.5TXP	Littelfuse Inc.	2.5	250	Slow Blow	5mm x 20mm	35	23.25	0.0219	Active	RoHS3 Compliant
021902.5MXAP	Littelfuse	2.5	250	Slow Blow	5mm x 20mm	150	138	0.0305	Active	RoHS3 Compliant
BK1/GMC-2.5-R	Eaton - Electronics Division	2.5	250	Medium Blow	5mm x 20mm	100	13	0.035	Active	RoHS3 Compliant
BK1/GMD-2.5-R	Eaton - Electronics Division	2.5	250	Slow Blow	5mm x 20mm	100	94	0.0905	Active	RoHS3 Compliant
GDC-2.5A	Eaton - Electronics Division	2.5	250	Slow Blow	5mm x 20mm	35	59.4	0.0255	Active	RoHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: 5ET 2.5-R (Bel Fuse Inc.)

The 5ET 2.5-R is the direct active equivalent of the obsolete 5ET 2.5. This part maintains identical electrical specifications (2.5 A, 250 V, 150 A breaking capacity, 137 melting I²t) and mechanical package (5mm x 20mm). The 5ET 2.5-R is RoHS3 compliant and carries active product status with 1441 units in stock. Certifications include CCC, CE, CSA, cURus, SEMKO, and VDE. This part requires no design modification and provides direct pin-for-pin compatibility.

Secondary Recommendation: 021902.5MXAP (Littelfuse)

The Littelfuse 021902.5MXAP provides parametric equivalence with matching electrical performance (2.5 A, 250 V, 150 A breaking capacity, 138 melting I²t). This part is RoHS3 compliant and active. Dimensional tolerance is 5.20mm diameter versus 5.10mm for the original part; holder compatibility must be verified. Certifications include CCC, CE, CSA, PSE, SEMKO, UL, and VDE. This option is suitable when Bel Fuse supply is constrained.

Alternative Consideration: 5ST 2.5-R or 5TT 2.5-R (Bel Fuse Inc.)

These parametric equivalents from Bel Fuse maintain the 2.5 A, 250 V, 5mm x 20mm specifications but differ in breaking capacity and melting I²t values. The 5ST 2.5-R provides 35 A breaking capacity with 20 melting I²t, while the 5TT 2.5-R provides 100 A breaking capacity with 45 melting I²t. These parts are suitable only when the application's fault current environment is confirmed to be within their respective breaking capacity ratings.

Not Recommended: BK1/GMC-2.5-R (Eaton)

The Eaton BK1/GMC-2.5-R exhibits medium blow response time, which differs from the slow blow characteristic of the original 5ET 2.5. This response time difference alters circuit protection behavior and is not suitable for direct substitution without circuit analysis and validation.

Frequently Asked Questions (FAQ)

Q: Can the 5ET 2.5-R be used as a direct replacement for the obsolete 5ET 2.5?

A: Yes. The 5ET 2.5-R is the active equivalent with identical electrical and mechanical specifications. No design modification is required.

Q: What is the difference between the 5ET 2.5-R and the 5ST 2.5-R?

A: Both maintain 2.5 A and 250 V ratings in a 5mm x 20mm package. The 5ET 2.5-R provides 150 A breaking capacity with 137 melting I²t, while the 5ST 2.5-R provides 35 A breaking capacity with 20 melting I²t. Selection depends on the application's maximum fault current.

Q: Are Littelfuse parts compatible with Bel Fuse holders?

A: Littelfuse 021802.5HXP and 021802.5TXP have a 5.20mm diameter versus 5.10mm for Bel Fuse parts. Holder compatibility must be verified with the specific holder manufacturer. The Littelfuse 021902.5MXAP maintains similar dimensional specifications and is more likely to be compatible.

Q: Why is the Eaton BK1/GMC-2.5-R not recommended?

A: The BK1/GMC-2.5-R has a medium blow response time, whereas the original 5ET 2.5 is slow blow. This difference affects circuit protection timing and inrush current handling, making it unsuitable for direct substitution without circuit validation.

Q: What certifications should I verify for my application?

A: Verify that the substitute part carries certifications required by your application's regulatory framework. The 5ET 2.5-R carries CCC, CE, CSA, cURus, SEMKO, and VDE certifications. Littelfuse alternatives carry UL certification in addition to regional certifications. Confirm alignment with your target market requirements.

Q: Is the 5ET 2.5-R RoHS compliant?

A: Yes. The 5ET 2.5-R is RoHS3 compliant, whereas the original 5ET 2.5 is RoHS non-compliant. This compliance improvement is beneficial for applications subject to RoHS regulations.

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