BK/MDL-4 Glass Cartridge Fuse 4A 250VAC Equivalent & Substitute Parts

Part Overview

The BK/MDL-4 is a 4 A, 250 V AC/DC slow-blow glass cartridge fuse manufactured by Eaton Electronics Division. This component is classified as obsolete product status. The fuse requires a 3AB or 3AG holder and is designed for applications requiring overcurrent protection in 250 V AC circuits with a slow-blow response characteristic. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for ongoing system maintenance and new design implementations.

Key Parameters

Parameter	Value
Current Rating	4 A
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Fuse Type	Cartridge, Glass
Package / Case	3AB, 3AG, 1/4" x 1-1/4" (6.35mm x 31.75mm)
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	200 A

Substitute Part Grouping Explanation

Substitution of the BK/MDL-4 is determined by strict equivalence across the following electrical and mechanical parameters:

Critical Matching Parameters:

Current Rating: 4 A (exact match required)
Voltage Rating: 250 V AC (exact match required)
Response Time: Slow Blow (exact match required)
Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Breaking Capacity: 200 A (exact match required)

All substitute parts listed below meet these critical parameters. Substitutes are grouped into two categories: direct manufacturer equivalents from Eaton Electronics Division and parametric equivalents from Littelfuse Inc. All substitute parts maintain identical electrical performance and mechanical compatibility with the original BK/MDL-4 specification.

Parameter Comparison

Part Number	Manufacturer	Current (A)	Voltage (V AC)	Response	Package	Breaking Capacity (A)	Product Status	RoHS Status
BK/MDL-4	Eaton	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Obsolete	Non-compliant
BK/MDL-4-R	Eaton	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	ROHS3 Compliant
MDL-4-R	Eaton	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	ROHS3 Compliant
BK/MDL-4GX-R	Eaton	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	RoHS Compliant
BK/MDQ-4	Eaton	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	Non-compliant
MDQ-4	Eaton	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	Non-compliant
0313004.HXIDP	Littelfuse	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	ROHS3 Compliant
0313004.HXP	Littelfuse	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	ROHS3 Compliant
0313004.MXP	Littelfuse	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	ROHS3 Compliant
0313004.VXIDP	Littelfuse	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	ROHS3 Compliant
0313004.VXP	Littelfuse	4	250	Slow Blow	3AB, 3AG, 1/4" x 1-1/4"	200	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation - Eaton Direct Equivalents:

For applications requiring continuity with the original Eaton product line, BK/MDL-4-R or MDL-4-R are the preferred direct substitutes. Both parts are active products with ROHS3 compliance, addressing the RoHS non-compliance limitation of the obsolete BK/MDL-4. These parts maintain identical electrical and mechanical specifications while offering improved regulatory compliance and current inventory availability (2092 and 822 units respectively).

Secondary Recommendation - Eaton Alternative Series:

BK/MDL-4GX-R and BK/MDQ-4 / MDQ-4 provide active product alternatives within the Eaton portfolio. BK/MDL-4GX-R offers RoHS compliance. The MDQ series (BK/MDQ-4 and MDQ-4) maintains the same electrical performance with active product status, though RoHS compliance differs.

Cross-Manufacturer Equivalents - Littelfuse 313 Series:

The Littelfuse 313 series fuses (0313004.HXIDP, 0313004.HXP, 0313004.MXP, 0313004.VXIDP, 0313004.VXP) provide parametric equivalence with extended operating temperature range (-55°C to 125°C) and ROHS3 compliance. These parts are certified by CE, CSA, K-MARK, PSE, and UL. The 0313004.MXP variant offers the highest inventory availability (3952 units).

Compliance Considerations:

All recommended substitutes maintain the required electrical ratings and mechanical package compatibility. For new designs or systems requiring RoHS compliance, Littelfuse 313 series or Eaton RoHS-compliant variants (BK/MDL-4-R, MDL-4-R, BK/MDL-4GX-R) are appropriate selections. For legacy system maintenance where RoHS compliance is not mandated, all listed substitutes are electrically and mechanically compatible.

Frequently Asked Questions (FAQ)

Q: Can BK/MDL-4-R be used as a direct replacement for BK/MDL-4?

A: Yes. BK/MDL-4-R is a direct equivalent with identical electrical ratings (4 A, 250 V AC, slow-blow response) and mechanical package (3AB, 3AG, 1/4" x 1-1/4"). The primary difference is product status (active vs. obsolete) and RoHS compliance (ROHS3 vs. non-compliant). Both parts are functionally interchangeable in the same holder.

Q: What is the difference between MDL and MDQ series fuses?

A: Both MDL and MDQ series from Eaton meet the same electrical specifications for the 4 A, 250 V slow-blow application. The series designation reflects internal design variations. All listed MDL and MDQ variants are mechanically and electrically compatible with the original BK/MDL-4 specification.

Q: Are Littelfuse 313 series fuses compatible with Eaton 3AB/3AG holders?

A: Yes. The Littelfuse 0313004 series fuses share the identical 3AB, 3AG package specification (1/4" x 1-1/4" / 6.35mm x 31.75mm) and are mechanically compatible with standard 3AB and 3AG holders. Electrical performance is equivalent across all listed Littelfuse variants.

Q: Which substitute offers the best inventory availability?

A: The Littelfuse 0313004.MXP provides the highest current inventory with 3952 units in stock. Among Eaton products, BK/MDL-4-R offers 2092 units.

Q: Do all substitutes have the same breaking capacity?

A: Yes. All listed substitute parts maintain the 200 A breaking capacity @ rated voltage, matching the original BK/MDL-4 specification.

Q: What is the operating temperature range for substitute parts?

A: Eaton MDL and MDQ series fuses do not specify an operating temperature range in the provided data. Littelfuse 313 series fuses operate across -55°C to 125°C, providing an extended temperature capability for applications requiring wider thermal performance.

Q: Are all substitutes UL and CSA certified?

A: Yes. All listed substitute parts carry UL and CSA certifications. Littelfuse 313 series variants additionally include CE, K-MARK, and PSE certifications.

Q: Can I use RoHS non-compliant substitutes in new designs?

A: Substitution decisions based on RoHS compliance depend on application requirements and regulatory jurisdiction. BK/MDQ-4 and MDQ-4 are RoHS non-compliant but electrically and mechanically equivalent. For applications requiring RoHS compliance, select BK/MDL-4-R, MDL-4-R, BK/MDL-4GX-R, or any Littelfuse 313 series variant.

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