Equivalent & Substitute Parts for BK/GMC-4A Glass Cartridge Fuse

Part Overview

The BK/GMC-4A is a 4 A, 125 V AC/DC glass cartridge fuse manufactured by Eaton - Electronics Division, designed for 5mm x 20mm holder applications. This fuse features medium blow response characteristics and a breaking capacity of 10 kA at rated voltage. The product is currently obsolete, with 872 pieces available in new original stock. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary to ensure continued availability and long-term supply chain reliability for replacement and new design applications.

Key Parameters

Parameter	Value
Current Rating	4 A
Voltage Rating (AC)	125 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Medium Blow
Breaking Capacity @ Rated Voltage	10 kA
Mounting Type	Requires Holder
Size / Dimension	0.205" Dia x 0.787" L (5.20mm x 20.00mm)

Substitute Part Grouping Explanation

Substitution for the BK/GMC-4A is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Current Rating: 4 A (exact match required)
Voltage Rating (AC): 125 V (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Mounting Type: Requires Holder (exact match required)
Breaking Capacity @ Rated Voltage: 10 kA (exact match required)

Secondary Consideration:

Response Time: Medium Blow is the primary characteristic; however, slow blow variants are listed as similar substitutes where all primary criteria are met.

Substitute parts are grouped into two categories:

Direct Equivalents (Active Status): Parts with identical electrical and mechanical specifications from Eaton - Electronics Division that maintain active product status.
Parametric Equivalents (Cross-Manufacturer): Parts from Littelfuse Inc. that match all critical electrical and mechanical parameters while maintaining compatibility with 5mm x 20mm holder systems.

Parameter Comparison

Part Number	Manufacturer	Current (A)	Voltage (V AC)	Response Time	Package	Breaking Capacity (kA)	Melting I²t	DC Cold Resistance (Ω)	Product Status	RoHS Status
BK/GMC-4A	Eaton	4	125	Medium Blow	5x20mm	10	36	0.019	Obsolete	Non-compliant
BK/GMC-4-R	Eaton	4	125	Medium Blow	5x20mm	10	36	0.019	Active	ROHS3 Compliant
BK1/GMC-4-R	Eaton	4	125	Medium Blow	5x20mm	10	36	0.019	Active	ROHS3 Compliant
GMC-4-R	Eaton	4	125	Medium Blow	5x20mm	10	36	0.019	Active	ROHS3 Compliant
0233004.MXBP	Littelfuse	4	125	Medium Blow	5x20mm	10	51.61	0.0293	Active	ROHS3 Compliant
0239004.HXP	Littelfuse	4	125	Slow Blow	5x20mm	10	270.703	0.0312	Active	ROHS3 Compliant
0232004.MX125P	Littelfuse	4	125	Medium Blow	5x20mm	10	37.73	0.0174	Active	ROHS3 Compliant
0233004.MXF11P	Littelfuse	4	125	Medium Blow	5x20mm	10	51.61	0.0293	Active	ROHS3 Compliant
0233004.MXF21P	Littelfuse	4	125	Medium Blow	5x20mm	10	51.61	0.0293	Active	ROHS3 Compliant
0233004.MXP	Littelfuse	4	125	Medium Blow	5x20mm	10	51.61	0.0293	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation - Eaton Direct Equivalents:

The BK/GMC-4-R, BK1/GMC-4-R, and GMC-4-R from Eaton - Electronics Division are direct functional equivalents with identical electrical and mechanical specifications to the obsolete BK/GMC-4A. These parts maintain active product status and are ROHS3 compliant, providing superior long-term supply chain continuity. Selection among these three Eaton variants should be based on packaging availability and internal procurement specifications.

Secondary Recommendation - Littelfuse Cross-Manufacturer Equivalents:

The 0233004.MXP, 0233004.MXF11P, 0233004.MXF21P, and 0233004.MXBP from Littelfuse Inc. are parametric equivalents that satisfy all critical electrical and mechanical requirements. These parts are active products with ROHS3 compliance and extended operating temperature ranges (-55°C to 125°C). The melting I²t value of 51.61 differs from the original 36, reflecting manufacturing process variations between suppliers while maintaining functional compatibility within the 5mm x 20mm holder system.

Alternative Response Characteristic:

The 0239004.HXP from Littelfuse Inc. is a slow blow variant that meets all dimensional and electrical parameters but features a significantly higher melting I²t of 270.703. This part is suitable only for applications where slow blow response is acceptable or required.

Tertiary Option:

The 0232004.MX125P from Littelfuse Inc. is a medium blow equivalent with a melting I²t of 37.73, closely matching the original BK/GMC-4A specification of 36. This part offers the closest thermal response profile to the obsolete original.

All recommended substitutes carry CSA, KC, MITI, and UL certifications, ensuring regulatory compliance across major markets.

Frequently Asked Questions (FAQ)

Q: Can I use BK/GMC-4-R as a direct replacement for BK/GMC-4A?

A: Yes. The BK/GMC-4-R is a direct functional equivalent with identical current rating (4 A), voltage rating (125 V AC), package dimensions (5mm x 20mm), response time (medium blow), and breaking capacity (10 kA). The primary difference is product status (active vs. obsolete) and RoHS compliance (ROHS3 compliant vs. non-compliant).

Q: What is the difference between the Eaton GMC-4-R variants (BK/GMC-4-R, BK1/GMC-4-R, GMC-4-R)?

A: All three variants are functionally identical with the same electrical and mechanical specifications. The differences are in part number designation and internal Eaton product line management. Selection should follow your organization's procurement specifications or consult with your supplier for availability and lead time.

Q: Can I substitute a Littelfuse part for the Eaton BK/GMC-4A?

A: Yes, Littelfuse parts 0233004.MXP, 0233004.MXF11P, 0233004.MXF21P, and 0233004.MXBP are parametric equivalents that meet all critical electrical and mechanical requirements. All are compatible with 5mm x 20mm holder systems. The melting I²t values differ slightly (51.61 vs. 36), but this reflects normal manufacturing variation between suppliers and does not affect functional compatibility.

Q: What is the significance of the melting I²t parameter?

A: Melting I²t defines the thermal energy required to melt the fuse element and is directly related to the fuse's response time and thermal characteristics. The original BK/GMC-4A has a melting I²t of 36. Littelfuse equivalents have values ranging from 37.73 to 51.61. These variations are within acceptable ranges for medium blow fuses and do not compromise circuit protection performance in standard applications.

Q: Should I use the 0239004.HXP slow blow variant?

A: The 0239004.HXP is a slow blow fuse with a melting I²t of 270.703, significantly higher than the original medium blow specification. Use this part only if your application specifically requires slow blow response characteristics. For standard applications requiring medium blow response, use the medium blow equivalents listed above.

Q: Are all substitute parts RoHS compliant?

A: The original BK/GMC-4A is RoHS non-compliant. All recommended substitute parts (Eaton and Littelfuse) are ROHS3 compliant, meeting current environmental regulations.

Q: What certifications do the substitute parts carry?

A: All substitute parts carry CSA, KC, MITI, and UL certifications. Littelfuse parts additionally carry CE and PSE certifications. These certifications ensure regulatory compliance across North American, European, and Asian markets.

Q: Can I mix Eaton and Littelfuse fuses in the same circuit or application?

A: Yes, provided all electrical and mechanical parameters match the circuit requirements. Both manufacturers' parts meet identical current, voltage, package, and breaking capacity specifications. However, maintain consistency within a single circuit or system where possible to simplify inventory management and maintenance procedures.

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

A: The original BK/GMC-4A does not specify an operating temperature range. Littelfuse equivalents operate from -55°C to 125°C, providing extended temperature performance. Eaton equivalents do not specify an operating temperature range in the provided data.

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