5VT 1.25-R Equivalent & Substitute Parts

Part Overview

The 5VT 1.25-R is a 1.25 A, 250 V AC/DC glass cartridge fuse manufactured by Bel Fuse Inc. in a 5mm x 20mm package format. This fuse is classified as obsolete, necessitating identification of active equivalent and substitute parts from current manufacturers. The 5VT 1.25-R requires a dedicated fuse holder for installation and operates across a temperature range of -55°C to 125°C with slow-blow response characteristics.

Key Parameters

Parameter	Value
Current Rating	1.25 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Slow Blow
Mounting Type	Requires Holder
Operating Temperature	-55°C ~ 125°C
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitution of the 5VT 1.25-R is determined by strict equivalence across the following parameters: current rating (1.25 A), voltage rating (250 V AC), fuse type (cartridge glass), package dimensions (5mm x 20mm), response time (slow blow), and mounting configuration (requires holder). All identified substitute parts maintain these core electrical and mechanical specifications. Variations in secondary parameters such as breaking capacity, melting I²t, DC cold resistance, and approval agency certifications do not preclude substitution when the primary parameters remain constant.

Parameter Comparison

Parameter	5VT 1.25-R (Bel Fuse)	02131.25MXP (Littelfuse)	02181.25TXP (Littelfuse)	02391.25HXP (Littelfuse)	BK1/GMD-1.25-R (Eaton)	GDC-1.25A (Eaton)
Current Rating (Amps)	1.25 A	1.25 A	1.25 A	1.25 A	1.25 A	1.25 A
Voltage Rating - AC	250 V	250 V	250 V	250 V	250 V	250 V
Fuse Type	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass	Cartridge, Glass
Package / Case	5mm x 20mm	5mm x 20mm	5mm x 20mm	5mm x 20mm	5mm x 20mm	5mm x 20mm
Response Time	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow	Slow Blow
Mounting Type	Requires Holder	Requires Holder	Requires Holder	Requires Holder	Requires Holder	Requires Holder
Operating Temperature	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-55°C ~ 125°C	-	-
Breaking Capacity @ Rated Voltage	35A	35A	35A	100A	100A	35A
Melting I²t	42	27.15	12.65	19.525	16	10.05
DC Cold Resistance (Ohms)	0.08	0.0817	0.0446	0.198	0.1995	0.06
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	Not Specified
Product Status	Obsolete	Active	Active	Active	Active	Active

Engineering Selection Recommendations

All six substitute parts maintain electrical and mechanical equivalence to the 5VT 1.25-R across primary specification parameters. Selection among active alternatives depends on compliance requirements and approval agency certifications relevant to the application.

The Littelfuse 02131.25MXP (Series 213) provides the broadest approval agency coverage, including BSI, CCC, CE, CSA, PSE, SEMKO, UR, and VDE certifications. This part is suitable for applications requiring multi-regional compliance.

The Littelfuse 02181.25TXP (Series 218) offers certifications including CCC, CE, CSA, KC, PSE, SEMKO, UL, and VDE, with the lowest melting I²t value (12.65) among Littelfuse options.

The Littelfuse 02391.25HXP (Series 239) features the highest breaking capacity (100A) and certifications from CE, CSA, KC, PSE, and UL.

The Eaton BK1/GMD-1.25-R (Series GMD) provides 100A breaking capacity with CSA, PSE/JET, and UL certifications, suitable for applications requiring these specific approvals.

The Eaton GDC-1.25A (Series GDC) offers the lowest DC cold resistance (0.06 Ohms) and certifications from cURus, IMQ, and MITI/JET, appropriate for applications requiring these regional approvals.

Frequently Asked Questions (FAQ)

Q: Can the 5VT 1.25-R be directly replaced with any of these substitute parts?

A: Yes. All substitute parts maintain identical current rating (1.25 A), voltage rating (250 V AC), fuse type (cartridge glass), package dimensions (5mm x 20mm), response time (slow blow), and mounting configuration (requires holder). Direct mechanical and electrical substitution is supported.

Q: What is the significance of the different melting I²t values?

A: Melting I²t represents the thermal energy required to melt the fuse element. Variations in this parameter reflect different fuse element designs among manufacturers but do not affect substitution eligibility when all primary specifications remain constant.

Q: Do all substitute parts require the same fuse holder as the 5VT 1.25-R?

A: Yes. All substitute parts are cartridge glass fuses in the 5mm x 20mm package format and require a compatible 5mm x 20mm fuse holder. Existing holder installations are compatible with all listed substitutes.

Q: Which substitute part should be selected for international applications?

A: The Littelfuse 02131.25MXP (Series 213) provides the most comprehensive approval agency coverage across multiple regions, including BSI, CCC, CE, CSA, PSE, SEMKO, UR, and VDE certifications.

Q: Are there differences in operating temperature ranges among the substitutes?

A: The Littelfuse parts (02131.25MXP, 02181.25TXP, 02391.25HXP) specify -55°C to 125°C operating temperature. The Eaton parts (BK1/GMD-1.25-R, GDC-1.25A) do not specify operating temperature limits in the provided data.

Q: What is the difference between 35A and 100A breaking capacity?

A: Breaking capacity indicates the maximum fault current the fuse can safely interrupt. The 02391.25HXP, BK1/GMD-1.25-R, and GDC-1.25A offer 100A breaking capacity, while the 5VT 1.25-R, 02131.25MXP, and 02181.25TXP offer 35A. Selection depends on the maximum fault current expected in the application circuit.

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