3AG 4 Glass Cartridge Fuse - Equivalent & Substitute Parts

Part Overview

The 3AG 4 is a 4 A, 250 V AC/DC fast-blow glass cartridge fuse manufactured by Bel Fuse Inc. This component is classified as obsolete, requiring identification of active equivalent alternatives for new designs and ongoing maintenance applications. The 3AG form factor (1/4" x 1-1/4") is a standard cartridge fuse package that requires a compatible holder (3AB or 3AG series). Substitute parts must maintain identical electrical ratings, mechanical dimensions, and holder compatibility to ensure direct replacement capability.

Substiute Parts

3AG 4

Bel Fuse Inc.In Stock: 9463AG 4 Datasheet

Current PartRFQ

3AG 4-R

Bel Fuse Inc.In Stock: 19473AG 4-R Datasheet

DirectRFQ

0034.5138

SCHURTER Inc.In Stock: 8700034.5138 Datasheet

Parametric EquivalentRFQ

FSA-4A

OptiFuseIn Stock: 5876FSA-4A Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the 3AG 4 fuse is determined by strict equivalence across the following critical parameters:

• Current Rating: Must be 4 A
• Voltage Rating: Must be 250 V AC minimum
• Response Characteristic: Must be Fast Blow
• Physical Dimensions: Must be 1/4" x 1-1/4" (6.35mm x 31.80mm) to fit 3AB/3AG holders
• Fuse Type: Must be glass cartridge construction
• Breaking Capacity: Must be 200 A at rated voltage

All substitute parts listed below meet these electrical and mechanical requirements and are compatible with existing 3AB and 3AG holder installations.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: 3AG 4-R (Bel Fuse Inc.)

The 3AG 4-R is the direct manufacturer equivalent from Bel Fuse Inc. and carries active product status. This part maintains identical electrical and mechanical specifications to the original 3AG 4 while offering ROHS3 compliance and expanded certification coverage (cULus added). Inventory availability is substantial (1,840 pcs), supporting both immediate and sustained procurement requirements.

Secondary Recommendation: FSA-4A (OptiFuse)

The FSA-4A provides parametric equivalence with active product status and ROHS3 compliance. This part is certified to UL 248 and cULus standards. Inventory availability is highest among all alternatives (5,807 pcs), ensuring supply continuity. The FSA series is widely used in industrial and commercial applications requiring 4 A, 250 V fast-blow protection.

Alternative: 0034.5138 (SCHURTER Inc.)

The 0034.5138 meets all electrical and mechanical substitution criteria and carries ROHS3 compliance. However, this part is classified as obsolete, limiting its suitability for new designs despite current inventory availability (809 pcs). This option is suitable only for legacy system maintenance where supply of the original 3AG 4 is exhausted.

Frequently Asked Questions (FAQ)

Q: Can I use any of these substitute parts in my existing 3AB/3AG holder?

A: Yes. All substitute parts listed maintain the identical 1/4" x 1-1/4" (6.35mm x 31.80mm) physical dimensions and are designed for 3AB and 3AG holder compatibility. No mechanical modification is required.

Q: What is the difference between the 3AG 4 and 3AG 4-R?

A: Both parts are manufactured by Bel Fuse Inc. and share identical electrical ratings (4 A, 250 V AC/DC, fast-blow). The primary difference is product status: the 3AG 4 is obsolete, while the 3AG 4-R is active. The 3AG 4-R also includes ROHS3 compliance and expanded certifications (cULus). For new designs and ongoing procurement, the 3AG 4-R is the recommended choice.

Q: Are all substitute parts RoHS compliant?

A: The 3AG 4 original part is RoHS non-compliant. All three substitute parts (3AG 4-R, 0034.5138, and FSA-4A) are ROHS3 compliant, meeting current environmental and regulatory requirements.

Q: Which substitute has the best inventory availability?

A: The FSA-4A (OptiFuse) has the highest inventory level at 5,807 pcs. The 3AG 4-R (Bel Fuse Inc.) has 1,840 pcs available. Both support immediate and sustained procurement needs.

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

A: Yes. All substitute parts meet identical electrical specifications (4 A, 250 V, fast-blow, 200 A breaking capacity) and are mechanically compatible with the same holders. Mixing different manufacturers' parts within the same equipment is permissible from an electrical and mechanical standpoint.

Q: What certifications should I verify for my application?

A: Verify that the selected substitute part carries the certifications required by your application and regional standards. The 3AG 4-R supports CE, CSA, cULus, and PSE. The FSA-4A supports cULus and UL 248. The 0034.5138 supports CSA and UL. Cross-reference these certifications against your equipment's regulatory requirements.

Q: Is the melting I²t value important for substitution?

A: The melting I²t values provided (3AG 4: 36; FSA-4A: 43.65) indicate thermal energy absorption characteristics. Both values fall within acceptable ranges for 4 A fast-blow fuses. The slight variation does not affect compatibility in standard 3AB/3AG holder applications, but should be verified against specific circuit protection requirements if thermal coordination is critical.