MRF 4-BULK Equivalent & Substitute Parts

Part Overview

The MRF 4-BULK is a 4 A, 250 V AC/DC board mount fuse with fast blow response characteristics, manufactured by Bel Fuse Inc. This radial, can-style through-hole fuse is designed for circuit protection in industrial and electronic applications requiring reliable overcurrent protection. The part maintains active product status with 1065 units in current inventory. Equivalent and substitute parts are identified to support procurement flexibility, design redundancy, and supply chain continuity.

Substiute Parts

MRF 4-BULK

Bel Fuse Inc.In Stock: 1104MRF 4-BULK Datasheet

Current PartRFQ

SR-5-2A-BK

Eaton - Electronics DivisionIn Stock: 5007SR-5-2A-BK Datasheet

DirectRFQ

37014000000

Littelfuse Inc.In Stock: 93537014000000 Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the MRF 4-BULK is determined by the following critical parameters:

Primary Substitution Criteria:

• Current Rating: 4 A (exact match required for direct substitution)
• Voltage Rating (AC): 250 V (exact match required)
• Mounting Type: Through Hole
• Fuse Type: Board Mount (Cartridge Style Excluded)
• Package / Case: Radial, Can, Vertical

Secondary Compatibility Factors:

• Response Time: Fast Blow (preferred for equivalent function)
• Breaking Capacity @ Rated Voltage: 40 A (minimum acceptable)
• Operating Temperature Range: Must support application requirements
• Physical Dimensions: Mechanical fit within PCB layout constraints
• Regulatory Approvals: Compliance with applicable standards (AEC-Q200, CE, CSA, cULus, PSE, SEMKO, VDE)

Identified Substitutes:

1. 37014000000 (Littelfuse Inc., TR5® 370 Series) – Direct equivalent with matching current rating, voltage, response time, and breaking capacity. Dimensions vary slightly (0.335" Dia x 0.315" H vs. 0.329" Dia x 0.303" H). Operating temperature range differs (-40°C ~ 85°C vs. -55°C ~ 125°C). Melting I²t value is 6.7 (vs. 8 for MRF 4-BULK).

2. SR-5-2A-BK (Eaton - Electronics Division, SR-5 Series) – Partial substitute with reduced current rating (2 A vs. 4 A). Voltage rating matches (250 V). Response time differs (Slow Blow vs. Fast Blow). Dimensions and breaking capacity differ. This part is suitable only for applications requiring lower current protection.

Parameter Comparison

Engineering Selection Recommendations

Direct Equivalent (Recommended for 1:1 Replacement):

The 37014000000 (Littelfuse TR5® 370 Series) is the primary equivalent substitute for the MRF 4-BULK. Both parts share identical current rating (4 A), voltage rating (250 V), response time (Fast Blow), and breaking capacity (40 A). Physical dimensions are comparable with minor variations (0.335" Dia x 0.315" H vs. 0.329" Dia x 0.303" H), which typically accommodate standard PCB footprints. Both parts maintain ROHS3 compliance and active product status. The operating temperature range of the Littelfuse part (-40°C ~ 85°C) is narrower than the MRF 4-BULK (-55°C ~ 125°C); verify application temperature requirements before selection.

Conditional Substitute (Current Derating Required):

The SR-5-2A-BK (Eaton SR-5 Series) is a partial substitute suitable only for applications where the circuit protection requirement is 2 A or lower. This part cannot be used as a direct replacement for 4 A protection circuits due to its reduced current rating. The Slow Blow response time differs from the MRF 4-BULK's Fast Blow characteristic, affecting transient protection behavior. Selection of this part requires circuit redesign and thermal analysis.

Regulatory Compliance:

All three parts maintain ROHS3 compliance and active product status. The MRF 4-BULK carries broader regulatory approvals (AEC-Q200, CE, CSA, cULus, PSE, SEMKO, VDE) compared to the Littelfuse part (CCC, cURus, PSE, SEMKO, VDE) and Eaton part (CCC, cULus, KC-MARK, PSE, SEMKO, VDE). Verify that selected substitute meets application-specific certification requirements.

Frequently Asked Questions (FAQ)

Q: Can the SR-5-2A-BK be used as a direct replacement for the MRF 4-BULK?

A: No. The SR-5-2A-BK has a current rating of 2 A, while the MRF 4-BULK is rated for 4 A. Using a lower-rated fuse in a 4 A circuit will cause nuisance trips and inadequate circuit protection. The SR-5-2A-BK is suitable only for circuits designed for 2 A protection.

Q: What are the key differences between the MRF 4-BULK and the 37014000000?

A: Both parts share the same current rating (4 A), voltage rating (250 V), response time (Fast Blow), and breaking capacity (40 A). The primary differences are: physical dimensions (MRF 4-BULK: 0.329" Dia x 0.303" H; 37014000000: 0.335" Dia x 0.315" H), operating temperature range (MRF 4-BULK: -55°C ~ 125°C; 37014000000: -40°C ~ 85°C), and melting I²t value (MRF 4-BULK: 8; 37014000000: 6.7). Verify PCB layout compatibility and application temperature requirements before substitution.

Q: Does the MRF 4-BULK meet automotive qualification standards?

A: The MRF 4-BULK carries AEC-Q200 approval, indicating compliance with automotive reliability standards. The 37014000000 (Littelfuse) does not list AEC-Q200 approval. If automotive qualification is required, the MRF 4-BULK is the specified choice.

Q: Are there packaging differences between these parts?

A: The MRF 4-BULK is supplied in Bulk packaging. The 37014000000 is supplied in Cut Tape (CT) packaging. The SR-5-2A-BK is supplied in Bulk packaging. Packaging format affects procurement, handling, and assembly processes but does not impact electrical or mechanical compatibility.

Q: What is the significance of the melting I²t value in fuse selection?

A: The melting I²t value indicates the thermal energy required to melt the fuse element. The MRF 4-BULK has a melting I²t of 8, while the 37014000000 has 6.7. Lower I²t values result in faster response to overcurrent conditions. The SR-5-2A-BK has a melting I²t of 30, reflecting its Slow Blow characteristic. Selection must align with circuit protection requirements and transient tolerance specifications.

Q: Can physical dimension differences affect PCB assembly?

A: Yes. The MRF 4-BULK measures 0.329" Dia x 0.303" H, while the 37014000000 measures 0.335" Dia x 0.315" H. These variations are typically within standard PCB footprint tolerances for radial through-hole components. However, verify mechanical clearance in confined layouts, particularly near adjacent components or heat-generating elements. The SR-5-2A-BK dimensions (0.335" Dia x 0.319" H) are comparable to the 37014000000.

Q: What operating temperature range should I consider for my application?

A: The MRF 4-BULK operates from -55°C to 125°C, providing the widest temperature range among the three parts. The 37014000000 and SR-5-2A-BK both operate from -40°C to 85°C. If your application requires operation below -40°C or above 85°C, the MRF 4-BULK is the only suitable option. Verify your circuit's thermal environment and component proximity to heat sources.