Bel Fuse Inc. 5MF 1 Glass Cartridge Fuse 1A 250VAC 5x20mm Equivalent & Substitute Parts

Part Overview

The Bel Fuse Inc. 5MF 1 is a 1 A, 250 V AC/DC fast-blow glass cartridge fuse in 5mm x 20mm form factor, designed for use with appropriate fuse holders. This part is classified as obsolete. Equivalent and substitute parts are necessary to maintain circuit protection functionality in applications where the original 5MF 1 is no longer available. Substitute parts must maintain electrical and mechanical compatibility based on current rating, voltage rating, response time, package dimensions, and mounting requirements.

Key Parameters

Parameter	5MF 1 Value
Current Rating	1 A
Voltage Rating (AC)	250 V
Response Time	Fast Blow
Package / Case	5mm x 20mm
Fuse Type	Cartridge, Glass
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	200A
Melting I²t	0.88
Operating Temperature Range	-55°C ~ 125°C
DC Cold Resistance	0.12 Ohms

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence in the following parameters:

Current Rating: 1 A (mandatory match)
Voltage Rating (AC): 250 V (mandatory match)
Response Time: Fast Blow (mandatory match)
Package / Case: 5mm x 20mm (mandatory match)
Fuse Type: Cartridge, Glass (mandatory match)
Mounting Type: Requires Holder (mandatory match)

Parts meeting all mandatory criteria are classified as direct equivalents or parametric equivalents. Parts with variations in secondary parameters (breaking capacity, melting I²t, operating temperature, or DC cold resistance) are classified as similar substitutes and require application-specific evaluation.

The following parts satisfy the mandatory substitution criteria:

Direct Manufacturer Equivalent: 5MF 1-R (Bel Fuse Inc.)

Parametric Equivalents: 5SF 1-R (Bel Fuse Inc.)

Similar Substitutes: 0034.3872 (SCHURTER Inc.), 0034.1516 (SCHURTER Inc.), 0217001.HXP (Littelfuse Inc.), 0235001.HXP (Littelfuse Inc.), BK1/S500-1-R (Eaton - Electronics Division), GDB-1A (Eaton - Electronics Division), S500-1-R (Eaton - Electronics Division)

Non-Equivalent: BP/GMA-1A (Eaton - Bussmann Electrical Division) — voltage rating is 125 V AC, not 250 V AC.

Parameter Comparison

Part Number	Manufacturer	Current Rating (A)	Voltage Rating (AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	Operating Temp (°C)	DC Cold Resistance (Ohms)	Product Status	RoHS Status
5MF 1	Bel Fuse Inc.	1	250	Fast Blow	5x20mm	200	0.88	-55 ~ 125	0.12	Obsolete	Non-compliant
5MF 1-R	Bel Fuse Inc.	1	250	Fast Blow	5x20mm	200	0.88	-55 ~ 125	0.118	Active	ROHS3 Compliant
5SF 1-R	Bel Fuse Inc.	1	250	Fast Blow	5x20mm	35	1.6	-55 ~ 125	0.09	Active	ROHS3 Compliant
0034.3872	SCHURTER Inc.	1	250	Fast Blow	5x20mm	35	0.68	-40 ~ 85	—	Active	ROHS3 Compliant
0034.1516	SCHURTER Inc.	1	250	Fast Blow	5x20mm	35	1.13	-55 ~ 125	—	Active	ROHS3 Compliant
0217001.HXP	Littelfuse Inc.	1	250	Fast Blow	5x20mm	35	1.045	-55 ~ 125	0.0964	Active	ROHS3 Compliant
0235001.HXP	Littelfuse	1	250	Fast Blow	5x20mm	100	0.4675	-55 ~ 125	0.153	Active	ROHS3 Compliant
BK1/S500-1-R	Eaton - Electronics Division	1	250	Fast Blow	5x20mm	35	0.6	—	0.125	Active	ROHS3 Compliant
GDB-1A	Eaton - Electronics Division	1	250	Fast Blow	5x20mm	35	0.6	—	0.125	Active	—
S500-1-R	Eaton - Electronics Division	1	250	Fast Blow	5x20mm	35	0.6	—	0.125	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: 5MF 1-R (Bel Fuse Inc.)

The 5MF 1-R is the direct manufacturer equivalent with identical electrical characteristics to the obsolete 5MF 1. It maintains the same 200A breaking capacity and 0.88 melting I²t. The part is active in production, ROHS3 compliant, and carries the same approval agencies (CE, CSA, cULus, PSE). DC cold resistance is 0.118 Ohms, negligibly different from the original 0.12 Ohms. This is the preferred direct replacement.

Secondary Recommendation: 5SF 1-R (Bel Fuse Inc.)

The 5SF 1-R is a parametric equivalent from the same manufacturer with identical current, voltage, response time, and package specifications. It differs in breaking capacity (35A vs. 200A) and melting I²t (1.6 vs. 0.88). This part is suitable for applications where the lower breaking capacity is acceptable. It is ROHS3 compliant and active in production.

Alternative Substitutes: SCHURTER, Littelfuse, and Eaton Parts

Parts 0034.3872, 0034.1516, 0217001.HXP, 0235001.HXP, BK1/S500-1-R, GDB-1A, and S500-1-R all meet the mandatory substitution criteria (1 A, 250 V AC, fast-blow, 5x20mm cartridge). These parts vary in breaking capacity, melting I²t, and operating temperature range. Selection among these alternatives depends on application-specific requirements for breaking capacity and thermal performance. All active parts listed are ROHS3 compliant.

Non-Equivalent: BP/GMA-1A

The BP/GMA-1A is not a suitable substitute. Although it matches current rating and package dimensions, its voltage rating is 125 V AC, not 250 V AC. This part is not electrically equivalent and must not be used as a replacement for the 5MF 1.

Frequently Asked Questions (FAQ)

Q: Can I use 5SF 1-R as a direct replacement for 5MF 1?

A: Yes, 5SF 1-R is electrically and mechanically compatible. Both are 1 A, 250 V AC fast-blow fuses in 5x20mm cartridge form. The 5SF 1-R has a lower breaking capacity (35A vs. 200A) and higher melting I²t (1.6 vs. 0.88). Verify that your application does not require the higher breaking capacity of the original part.

Q: What is the difference between breaking capacity and melting I²t?

A: Breaking capacity is the maximum current the fuse can safely interrupt at rated voltage. Melting I²t is a measure of the thermal energy required to melt the fuse element. Both parameters affect fuse performance under fault conditions. Application requirements determine which values are necessary.

Q: Are all substitute parts RoHS compliant?

A: Most active substitute parts listed are ROHS3 compliant. The original 5MF 1 is RoHS non-compliant. GDB-1A does not specify RoHS status in available data. Verify RoHS compliance requirements for your application before selection.

Q: Can I use parts with different operating temperature ranges?

A: The original 5MF 1 operates from -55°C to 125°C. Some substitutes (0034.3872) have a narrower range (-40°C to 85°C). Verify that the substitute part's operating temperature range is suitable for your application environment.

Q: Why is BP/GMA-1A listed as a substitute but not recommended?

A: BP/GMA-1A is listed in the original part's substitute field but has a voltage rating of 125 V AC, not 250 V AC. It does not meet the mandatory substitution criteria and is not electrically equivalent. It must not be used as a replacement.

Q: What certifications should I verify for my application?

A: The original 5MF 1 carries CE, CSA, PSE, and UL approvals. Substitute parts carry varying approval agencies. Verify that your selected substitute part carries the certifications required by your application and regional standards.

Q: Can I mix different substitute parts in the same circuit?

A: All substitute parts listed meet the mandatory electrical and mechanical criteria. However, mixing parts with different breaking capacities or melting I²t values in the same circuit may result in inconsistent fault protection. Use identical parts throughout a circuit for consistent performance.

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