BK/MDL-2-1/2 Glass Cartridge Fuse 2.5A 250VAC Equivalent & Substitute Parts

Part Overview

The BK/MDL-2-1/2 is a 2.5 A, 250 V AC/DC slow-blow glass cartridge fuse manufactured by Eaton Electronics Division. This fuse is designed for use with 3AB and 3AG holders and measures 0.250" diameter by 1.250" length (6.35mm x 31.75mm). The part is currently listed as obsolete with 1030 pieces in stock inventory. Due to its obsolete status, identifying equivalent and substitute parts is necessary to ensure continued availability and system reliability for applications requiring this fuse specification.

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"
Size / Dimension	0.250" Dia x 1.250" L (6.35mm x 31.75mm)
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	100A

Substitute Part Grouping Explanation

Substitution for the BK/MDL-2-1/2 is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

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

Secondary Compatibility Factors:

Breaking Capacity @ Rated Voltage: 100A or 35A (both acceptable within application scope)
Melting I²t: 48 to 130 (range acceptable for slow-blow characteristic)
DC Cold Resistance: 0.081 to 0.1005 Ohms (acceptable variance)

All substitute parts listed meet these criteria and are mechanically and electrically interchangeable with the main part within the specified electrical parameters.

Parameter Comparison

Part Number	Manufacturer	Current (A)	Voltage (V AC)	Response Time	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status
BK/MDL-2-1/2	Eaton	2.5	250	Slow Blow	100	63.1	0.096	Obsolete	Non-compliant
BK/MDL-2-1/2-R	Eaton	2.5	250	Slow Blow	100	63.1	0.081	Active	ROHS3 Compliant
MDL-2-1/2-R	Eaton	2.5	250	Slow Blow	100	63.1	0.081	Active	RoHS Compliant
BK/MDL-2-1/2EX-R	Eaton	2.5	250	Slow Blow	100	63.1	0.081	Active	RoHS Compliant
BK/MDQ-2-1/2	Eaton	2.5	250	Slow Blow	100	Not specified	0.1005	Active	Non-compliant
MDQ-2-1/2	Eaton	2.5	250	Slow Blow	35	Not specified	0.1005	Active	Not specified
0034.3421	SCHURTER Inc.	2.5	250	Slow Blow	35	48	Not specified	Obsolete	ROHS3 Compliant
031302.5HXP	Littelfuse Inc.	2.5	250	Slow Blow	100	130	0.0811	Active	ROHS3 Compliant
031302.5MXP	Littelfuse Inc.	2.5	250	Slow Blow	100	130	0.0811	Active	ROHS3 Compliant
031302.5VXP	Littelfuse Inc.	2.5	250	Slow Blow	100	130	0.0811	Active	ROHS3 Compliant

Engineering Selection Recommendations

Tier 1 - Direct Manufacturer Substitutes (Eaton Electronics Division):

BK/MDL-2-1/2-R, MDL-2-1/2-R, and BK/MDL-2-1/2EX-R are the primary recommended substitutes. All three parts are active products from the same manufacturer with identical electrical specifications to the obsolete BK/MDL-2-1/2. These parts feature improved RoHS compliance status and lower DC cold resistance (0.081 Ohms vs. 0.096 Ohms). BK/MDL-2-1/2-R and MDL-2-1/2-R carry CE certification in addition to CSA and UL approvals, providing broader regulatory acceptance.

Tier 2 - Eaton Alternative Series:

BK/MDQ-2-1/2 and MDQ-2-1/2 are active Eaton products within the MDQ series. Both maintain identical current, voltage, and response time specifications. BK/MDQ-2-1/2 retains 100A breaking capacity matching the original part. MDQ-2-1/2 features reduced breaking capacity (35A) and should be selected only when application requirements permit lower breaking capacity.

Tier 3 - Cross-Manufacturer Equivalents:

Littelfuse 031302.5HXP, 031302.5MXP, and 031302.5VXP are parametrically equivalent alternatives. All three are active products with 100A breaking capacity, ROHS3 compliance, and extended operating temperature range (-55°C to 125°C). These parts carry comprehensive international certifications (CE, CSA, K-MARK, PSE, UL for HXP and MXP; CE, CSA, KC, PSE, UL for VXP). Higher melting I²t values (130 vs. 63.1) indicate slightly different thermal response characteristics within the slow-blow classification.

Tier 4 - Legacy Cross-Manufacturer Option:

SCHURTER 0034.3421 is an obsolete product with 35A breaking capacity. This part should be considered only when inventory constraints or specific application requirements necessitate its use, as it shares obsolete status with the original part.

Compliance Considerations:

For new designs or systems requiring RoHS compliance, select from Tier 1 (BK/MDL-2-1/2-R, MDL-2-1/2-R, BK/MDL-2-1/2EX-R) or Tier 3 (Littelfuse 031302.5 series). For applications requiring CE certification, BK/MDL-2-1/2-R, MDL-2-1/2-R, or Littelfuse alternatives are appropriate.

Frequently Asked Questions (FAQ)

Q: Can BK/MDL-2-1/2-R be used as a direct replacement for BK/MDL-2-1/2?

A: Yes. BK/MDL-2-1/2-R is a direct substitute with identical electrical and mechanical specifications. Both parts are 2.5 A, 250 V AC/DC slow-blow glass cartridge fuses in 3AB/3AG package format. BK/MDL-2-1/2-R is an active product with improved RoHS compliance and is the recommended replacement for the obsolete BK/MDL-2-1/2.

Q: What is the difference between MDL-2-1/2-R and BK/MDL-2-1/2-R?

A: Both parts are electrically and mechanically identical with 2.5 A, 250 V specifications and 100A breaking capacity. The primary difference is packaging designation. MDL-2-1/2-R is supplied in bulk packaging, while BK/MDL-2-1/2-R includes the BK prefix designation. Both are active Eaton products with RoHS compliance and CSA/UL certifications.

Q: Can Littelfuse 031302.5MXP replace the Eaton BK/MDL-2-1/2?

A: Yes. The Littelfuse 031302.5MXP meets all critical substitution parameters: 2.5 A current rating, 250 V AC voltage rating, slow-blow response time, and 3AB/3AG package format with identical 0.250" x 1.250" dimensions. The part is active, ROHS3 compliant, and carries comprehensive international certifications. The higher melting I²t value (130 vs. 63.1) represents a variation within acceptable slow-blow fuse characteristics.

Q: What is the significance of breaking capacity differences (100A vs. 35A)?

A: Breaking capacity indicates the maximum fault current the fuse can safely interrupt at rated voltage. Parts with 100A breaking capacity (BK/MDL-2-1/2, BK/MDL-2-1/2-R, MDL-2-1/2-R, BK/MDL-2-1/2EX-R, BK/MDQ-2-1/2, Littelfuse 031302.5 series) are suitable for applications with higher available fault currents. Parts with 35A breaking capacity (MDQ-2-1/2, 0034.3421) are suitable only for applications where available fault current does not exceed 35A. Verify application requirements before selecting a substitute with reduced breaking capacity.

Q: Are all substitute parts compatible with existing 3AB and 3AG fuse holders?

A: Yes. All substitute parts listed maintain the 3AB/3AG package designation and 0.250" diameter x 1.250" length dimensions. Physical compatibility with existing holders is confirmed. Electrical compatibility is also confirmed across all parts, as all maintain 2.5 A current rating and 250 V AC voltage rating.

Q: Which substitute offers the best compliance profile for new equipment designs?

A: Littelfuse 031302.5MXP and 031302.5HXP offer the most comprehensive compliance profile. Both are ROHS3 compliant, REACH unaffected, and carry CE, CSA, K-MARK, PSE, and UL certifications. These parts also feature extended operating temperature range (-55°C to 125°C) and are active products with high inventory availability (9244 and 1241 pieces respectively).

Q: Can MDQ-2-1/2 be used in applications originally designed for BK/MDL-2-1/2?

A: MDQ-2-1/2 is electrically and mechanically compatible but features reduced breaking capacity (35A vs. 100A). This part is suitable only if application fault current analysis confirms available fault current does not exceed 35A. Verify system specifications before substitution.

Q: What is the difference between 031302.5HXP, 031302.5MXP, and 031302.5VXP?

A: All three Littelfuse parts are parametrically identical with 2.5 A, 250 V, slow-blow characteristics and 100A breaking capacity. The primary difference is certification scope: 031302.5HXP and 031302.5MXP carry K-MARK certification, while 031302.5VXP carries KC certification. All three are ROHS3 compliant and active products. Selection between these parts depends on specific regional certification requirements.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message