Equivalent & Substitute Parts for MDQ-2-1/2 Glass Cartridge Fuse

Part Overview

The MDQ-2-1/2 is a 2.5 A, 250 V AC/DC glass cartridge fuse manufactured by Eaton - Electronics Division. This slow-blow fuse is designed for applications requiring holder-based mounting in 3AB and 3AG configurations with dimensions of 1/4" x 1-1/4" (6.35mm x 31.75mm). The product maintains active status with 685 pieces in current inventory. Equivalent and substitute parts are identified to provide design flexibility, support obsolescence management, and accommodate supply chain variations while maintaining electrical and mechanical compatibility.

Key Parameters

Parameter	Value
Current Rating	2.5 A
Voltage Rating (AC)	250 V
Fuse Type	Cartridge, Glass
Response Time	Slow Blow
Package / Case	3AB, 3AG, 1/4" x 1-1/4"
Mounting Type	Requires Holder
Size / Dimension	0.250" Dia x 1.250" L (6.35mm x 31.75mm)
Approval Agencies	CSA, UL (minimum)

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following critical parameters:

Mandatory Matching Parameters:

Current Rating: 2.5 A
Voltage Rating (AC): 250 V
Fuse Type: Cartridge, Glass
Response Time: Slow Blow
Package / Case: 3AB, 3AG, 1/4" x 1-1/4"
Mounting Type: Requires Holder
Size / Dimension: 0.250" Dia x 1.250" L (6.35mm x 31.75mm)

Allowable Variation Parameters:

Breaking Capacity @ Rated Voltage: 35 A to 100 A
DC Cold Resistance: 0.0811 Ohms to 0.1005 Ohms
Approval Agencies: CSA, UL, CE, K-MARK, PSE
RoHS Status: Compliant or non-compliant
Melting I²t: 48 to 130

All identified substitute parts meet the mandatory matching criteria. Variations in breaking capacity, resistance, and certifications do not affect functional interchangeability within the specified electrical and mechanical envelope.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Current Rating (A)	Voltage Rating (AC)	Breaking Capacity @ Rated Voltage	DC Cold Resistance (Ohms)	Product Status	Approval Agencies	RoHS Status
MDQ-2-1/2	Eaton - Electronics Division	2.5	250 V	35 A	0.1005	Active	CSA, UL	Non-compliant
BK/MDL-2-1/2-R	Eaton - Electronics Division	2.5	250 V	100 A	0.081	Active	CE, CSA, UL	ROHS3 Compliant
BK/MDQ-2-1/2	Eaton - Electronics Division	2.5	250 V	100 A	0.1005	Active	CSA, UL	Non-compliant
0034.3421	SCHURTER Inc.	2.5	250 V	35 A	Not Specified	Obsolete	CSA	ROHS3 Compliant
031302.5HXP	Littelfuse Inc.	2.5	250 V	100 A	0.0811	Active	CE, CSA, K-MARK, PSE, UL	ROHS3 Compliant
031302.5MXP	Littelfuse Inc.	2.5	250 V	100 A	0.0811	Active	CE, CSA, K-MARK, PSE, UL	ROHS3 Compliant

Engineering Selection Recommendations

Primary Selection (Active Status, Full Compliance):

031302.5MXP (Littelfuse Inc.): Highest inventory availability (9,244 pieces), active product status, ROHS3 compliant, broadest approval agency coverage (CE, CSA, K-MARK, PSE, UL), 100 A breaking capacity.
031302.5HXP (Littelfuse Inc.): Active product status, ROHS3 compliant, comprehensive certifications, 100 A breaking capacity, 1,241 pieces in stock.

Secondary Selection (Active Status, Eaton Manufacturer):

BK/MDL-2-1/2-R (Eaton - Electronics Division): Active status, ROHS3 compliant, 100 A breaking capacity, 728 pieces available. Maintains manufacturer continuity with original part.
BK/MDQ-2-1/2 (Eaton - Electronics Division): Active status, 100 A breaking capacity, 1,048 pieces in stock. Same series as original part.

Not Recommended for New Designs:

0034.3421 (SCHURTER Inc.): Obsolete product status. Use only for legacy system maintenance where no alternative is available.

Selection should prioritize active product status and ROHS3 compliance for new applications. Littelfuse 313 series parts (031302.5MXP, 031302.5HXP) offer superior inventory depth and regulatory compliance.

Frequently Asked Questions (FAQ)

Q: Can I substitute MDQ-2-1/2 with any of the listed equivalent parts?

A: Yes. All listed parts meet the mandatory electrical and mechanical parameters: 2.5 A current rating, 250 V AC voltage rating, slow-blow response, glass cartridge type, and 3AB/3AG holder compatibility with 1/4" x 1-1/4" dimensions. Physical interchangeability is guaranteed.

Q: What is the difference between 35 A and 100 A breaking capacity?

A: Breaking capacity indicates the maximum fault current the fuse can safely interrupt without rupturing the cartridge. Both ratings are acceptable for this fuse category. The 100 A rating provides enhanced performance margin in high-fault-current environments. Selection depends on circuit design requirements, not interchangeability.

Q: Why is 0034.3421 marked obsolete?

A: SCHURTER Inc. has discontinued this product line. While electrically equivalent, it should be used only for replacement in existing systems. New designs should specify active alternatives from Eaton or Littelfuse.

Q: Does RoHS compliance affect electrical performance?

A: No. RoHS3 compliance indicates lead-free construction and environmental compliance. Electrical characteristics (current rating, voltage rating, response time) remain identical. Selection based on RoHS status depends on application regulatory requirements, not functional compatibility.

Q: Are Littelfuse 313 series parts (031302.5MXP and 031302.5HXP) interchangeable with each other?

A: Yes. Both parts share identical electrical specifications, dimensions, and certifications. Selection between them depends on inventory availability and supply chain preference. 031302.5MXP has significantly higher stock (9,244 vs. 1,241 pieces).

Q: What does DC Cold Resistance variation (0.0811 to 0.1005 Ohms) mean for circuit design?

A: DC cold resistance is measured at room temperature before fuse operation. The variation across equivalent parts is within normal manufacturing tolerance and does not affect circuit performance or fuse selection. Both values are acceptable for standard applications.

Q: Can I use these fuses in DC applications?

A: The specifications indicate 250 V AC/DC rating. All listed parts are rated for both AC and DC operation at 250 V. Verify circuit voltage does not exceed 250 V DC for safe operation.

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