Littelfuse 39212000000 Board Mount Fuse - Equivalent & Substitute Parts

Part Overview

The Littelfuse 39212000000 is a 2 A, 250 V AC/DC board mount fuse with slow blow response characteristics, designed for through-hole radial mounting in standard box packaging. This component is classified as Active product status and is widely stocked with 226,800 units available. Board mount fuses of this specification are essential in power distribution and circuit protection applications where controlled current limiting and thermal response are required. Substitute parts may be necessary due to supply constraints, regional availability, or specific application requirements within the defined electrical and mechanical parameters.

Substiute Parts

39212000000

Littelfuse Inc.In Stock: 22683339212000000 Datasheet

Current PartRFQ

RST 2-AMMO

Bel Fuse Inc.In Stock: 29654RST 2-AMMO Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the Littelfuse 39212000000 is determined by strict alignment of the following critical parameters:

• Current Rating: 2 A (exact match required)
• Voltage Rating (AC): 250 V (exact match required)
• Response Time: Slow Blow (exact match required)
• Mounting Type: Through Hole (exact match required)
• Fuse Type: Board Mount (Cartridge Style Excluded) (exact match required)
• Package / Case: Radial, Box (exact match required)

The Bel Fuse Inc. RST 2-AMMO meets all mandatory substitution criteria. Both parts share identical electrical ratings, response characteristics, and mechanical form factors. Variations in secondary parameters such as breaking capacity, melting I²t, operating temperature range, and approval agency certifications do not disqualify substitution when primary electrical and mechanical specifications are matched.

Parameter Comparison

Engineering Selection Recommendations

Both the Littelfuse 39212000000 and Bel Fuse RST 2-AMMO are Active product status components with full RoHS3 compliance and REACH unaffected status, making them suitable for current regulatory environments. The Littelfuse part carries approvals from CQC, cULus, KC, PSE/JET, SEMKO, and VDE. The Bel Fuse substitute carries approvals from CCC, CE, cURus, PSE, SEMKO, and VDE. Selection between these parts should be based on regional certification requirements and supply availability. The RST 2-AMMO offers extended low-temperature operating range (-55°C versus -40°C) and higher breaking capacity (100 A versus 25 A), which may provide additional margin in applications with demanding environmental or fault-current conditions.

Frequently Asked Questions (FAQ)

Q: Can the Bel Fuse RST 2-AMMO be used as a direct replacement for the Littelfuse 39212000000?

A: Yes. Both parts share identical current rating (2 A), voltage rating (250 V AC), response time (Slow Blow), mounting type (Through Hole), fuse type (Board Mount), and package configuration (Radial, Box). These are the primary substitution criteria for board mount fuses.

Q: What is the difference in breaking capacity between these parts?

A: The Littelfuse 39212000000 has a breaking capacity of 25 A at rated voltage, while the Bel Fuse RST 2-AMMO has 100 A. Breaking capacity defines the maximum fault current the fuse can safely interrupt. The higher breaking capacity of the RST 2-AMMO does not affect substitution eligibility but may provide additional safety margin in high-fault-current applications.

Q: Are there differences in operating temperature ranges?

A: Yes. The Littelfuse part operates from -40°C to 125°C, while the Bel Fuse part operates from -55°C to 125°C. The extended low-temperature range of the RST 2-AMMO may be advantageous in cold environment applications, but both parts meet standard industrial temperature requirements.

Q: Do the approval certifications differ between these parts?

A: Yes. The Littelfuse 39212000000 carries CQC, cULus, KC, PSE/JET, SEMKO, and VDE approvals. The Bel Fuse RST 2-AMMO carries CCC, CE, cURus, PSE, SEMKO, and VDE approvals. Selection should account for regional regulatory requirements specific to your application market.

Q: Is the physical size identical between these parts?

A: No. The Littelfuse part measures 0.335" L x 0.157" W x 0.315" H (8.50mm x 4.00mm x 8.00mm), while the Bel Fuse part measures 0.329" L x 0.157" W x 0.303" H (8.35mm x 4.00mm x 7.70mm). Both are radial box package configurations with minor dimensional variation. Verify PCB footprint compatibility before substitution.

Q: What is the difference in melting I²t values?

A: The Littelfuse 39212000000 has a melting I²t of 21, while the Bel Fuse RST 2-AMMO has 27. Melting I²t indicates the thermal energy required to melt the fuse element. The higher value in the RST 2-AMMO reflects slightly different thermal characteristics but does not affect the 2 A current rating or slow blow response classification.