3JS 4-R Equivalent & Substitute Parts Reference

Part Overview

The 3JS 4-R is a 4A glass cartridge fuse manufactured by Bel Fuse Inc., rated for 350V AC and 140V DC operation. This slow-blow fuse is designed for through-hole mounting in the 2AG package format (5mm x 15mm axial). The part maintains active product status with 1756 units in current inventory. Equivalent and substitute parts are identified to support procurement flexibility, design revisions, or supply chain continuity when the primary part becomes unavailable or when application requirements permit alternative electrical characteristics within acceptable parameters.

Substiute Parts

3JS 4-R

Bel Fuse Inc.In Stock: 17693JS 4-R Datasheet

Current PartRFQ

0209004.MXEP

Littelfuse Inc.In Stock: 14000209004.MXEP Datasheet

SimilarRFQ

0230004.MXP

Littelfuse Inc.In Stock: 40410230004.MXP Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 3JS 4-R is determined by the following critical parameters:

Primary Matching Criteria:

• Current Rating: 4 A (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Response Time: Slow Blow (exact match required)
• Mounting Type: Through Hole (exact match required)
• Package Format: 2AG or compatible axial cartridge (5mm x 15mm nominal dimensions)
• Operating Temperature Range: -55°C ~ 125°C (minimum requirement)

Voltage Compatibility Criteria:

• AC Voltage Rating: Minimum 350 V required for direct substitution
• DC Voltage Rating: Minimum 140 V required for direct substitution
• Parts with lower voltage ratings are acceptable only in applications where the circuit operates below the substitute part's rated voltage

Secondary Considerations:

• Breaking Capacity: Minimum 100A AC required
• Melting I²t: Values between 86 and 148 are acceptable within slow-blow fuse performance envelope
• DC Cold Resistance: Nominal range 0.0258 to 0.026 Ohms acceptable
• RoHS and regulatory compliance maintained across all substitutes

The identified substitute parts meet the primary matching criteria with noted voltage derating considerations for the 0230004.MXP variant.

Parameter Comparison

Engineering Selection Recommendations

0209004.MXEP (Littelfuse 209 Series): This substitute maintains full electrical compatibility with the 3JS 4-R across all critical parameters. The 350V AC rating matches the primary part exactly. Physical dimensions are nominally equivalent (4.70mm x 14.48mm versus 5.50mm x 15.00mm), permitting direct socket compatibility in standard 2AG fuse holders. The elevated melting I²t value (148 versus 86) represents a slightly slower thermal response but remains within the slow-blow classification. Regulatory compliance includes CE, cULus, and PSE certifications. This part is recommended as the primary substitute for direct replacement applications.

0230004.MXP (Littelfuse 230 Series): This substitute is suitable only for applications where circuit voltage does not exceed 125V AC/DC. The significantly reduced voltage rating (125V AC/125V DC versus 350V AC/140V DC) restricts its use to lower-voltage circuits. The non-standard package designation and smaller physical dimensions (4.50mm x 14.50mm) may require mechanical verification for socket fit, though axial orientation is maintained. The superior breaking capacity (400A) and expanded regulatory approval (UL addition) provide enhanced performance in compatible voltage domains. This part is recommended only when application voltage requirements are confirmed below 125V AC/DC.

Both substitutes maintain ROHS3 compliance, slow-blow response characteristics, and through-hole mounting configuration. Product status is active for both alternatives, ensuring continued availability.

Frequently Asked Questions (FAQ)

Q: Can the 0209004.MXEP be used as a direct replacement for the 3JS 4-R?

A: Yes. The 0209004.MXEP matches the 3JS 4-R in current rating (4A), voltage rating (350V AC), fuse type (cartridge glass), response time (slow blow), and package format (2AG, 5mm x 15mm axial). Physical dimensions are nominally compatible with standard 2AG fuse holders. The slightly higher melting I²t (148 versus 86) remains within acceptable slow-blow performance parameters.

Q: Why is the 0230004.MXP listed as a substitute if it has a lower voltage rating?

A: The 0230004.MXP is included as a substitute for applications where circuit voltage does not exceed 125V AC/DC. It meets all other critical parameters: 4A current rating, cartridge glass type, slow-blow response, and through-hole mounting. Substitution is valid only when the application voltage requirement is confirmed below the 125V AC/DC rating. Using this part in circuits exceeding 125V would violate electrical safety requirements.

Q: Are there physical compatibility concerns with the substitute parts?

A: The 0209004.MXEP maintains standard 2AG package dimensions (4.70mm x 14.48mm) and is directly compatible with 2AG fuse holders. The 0230004.MXP uses a non-standard package (4.50mm x 14.50mm) and should be mechanically verified for fit in the target fuse holder before deployment, though axial orientation is maintained across all three parts.

Q: What is the significance of the melting I²t difference between the main part and substitutes?

A: The melting I²t value characterizes the thermal response of the fuse element. The 3JS 4-R has a melting I²t of 86, while both Littelfuse substitutes have a value of 148. Both values fall within the slow-blow classification. The higher I²t in the substitutes indicates a slightly slower thermal response to transient overcurrent conditions. This difference is acceptable for most applications but should be verified if the circuit design depends on precise thermal response timing.

Q: Are all three parts RoHS compliant?

A: Yes. The 3JS 4-R, 0209004.MXEP, and 0230004.MXP are all ROHS3 compliant. All three parts are also REACH unaffected and carry EAR99 ECCN classification.

Q: Which regulatory certifications are common across all three parts?

A: CE and PSE certifications are present on all three parts. The 3JS 4-R adds CSA and cURus approvals. The 0209004.MXEP includes cULus certification. The 0230004.MXP includes CSA and UL certifications. Application requirements should determine whether specific certifications are mandatory for your design.