5MT 800-R Glass Cartridge Fuse Equivalent & Substitute Parts

Part Overview

The 5MT 800-R is an 800 mA, 250 V AC/DC glass cartridge fuse manufactured by Bel Fuse Inc. in a 5mm x 20mm form factor. This component is classified as obsolete, making equivalent substitute parts necessary for ongoing system maintenance and new design implementations. The fuse requires a compatible holder for installation and operates across a temperature range of -55°C to 125°C with medium blow response characteristics.

Substiute Parts

5MT 800-R

Bel Fuse Inc.In Stock: 11175MT 800-R Datasheet

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20108000001

Littelfuse Inc.In Stock: 117520108000001 Datasheet

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20108000021

Littelfuse Inc.In Stock: 76520108000021 Datasheet

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BK/GMC-800-R

Eaton - Electronics DivisionIn Stock: 1053BK/GMC-800-R Datasheet

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BK1/GMC-800-R

Eaton - Electronics DivisionIn Stock: 951BK1/GMC-800-R Datasheet

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GMC-800-R

Eaton - Electronics DivisionIn Stock: 973GMC-800-R Datasheet

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Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the 5MT 800-R is determined by strict alignment with the following electrical and mechanical parameters:

• Current Rating: 800 mA (exact match required)
• Voltage Rating: 250 V AC (exact match required)
• Package Dimensions: 5mm x 20mm (exact match required)
• Fuse Type: Cartridge, Glass (exact match required)
• Response Time: Medium Blow (exact match required)
• Mounting Configuration: Requires Holder (exact match required)

All five substitute parts listed meet these core criteria. Variations in breaking capacity, melting I²t, DC cold resistance, and operating temperature ranges are secondary parameters that may influence selection based on specific application requirements but do not disqualify substitution eligibility.

Parameter Comparison

Engineering Selection Recommendations

All five substitute parts satisfy the core electrical and mechanical requirements for direct substitution with the 5MT 800-R. Selection among these alternatives should be based on the following factors:

Product Availability and Status: The Littelfuse 20108000001 and 20108000021 parts, along with all three Eaton GMC series variants (BK/GMC-800-R, BK1/GMC-800-R, GMC-800-R), are classified as active products with current manufacturing support. This ensures long-term availability and supply chain continuity compared to the obsolete 5MT 800-R.

Regulatory Compliance: The Littelfuse parts carry cULus certification. The Eaton GMC series parts carry CSA, UL, and KC certifications. The original 5MT 800-R carries CE, CSA, and cULus certifications. Selection should align with the specific regulatory requirements of the target application and geographic market.

Thermal Operating Range: The original 5MT 800-R operates from -55°C to 125°C. The Littelfuse alternatives operate from -25°C to 70°C. Applications requiring extended low-temperature operation below -25°C should account for this limitation when selecting Littelfuse substitutes. Eaton GMC series parts do not specify operating temperature limits in the provided data.

Breaking Capacity: The Littelfuse 20108000001 and 20108000021 provide 80A breaking capacity, compared to 35A for the original 5MT 800-R and Eaton GMC series. Higher breaking capacity provides additional safety margin in high-fault-current environments.

DC Cold Resistance: The Eaton GMC series exhibits lower DC cold resistance (0.18 Ohms) compared to the original 5MT 800-R (0.261 Ohms), resulting in reduced resistive heating during normal operation.

Frequently Asked Questions (FAQ)

Q: Can the Littelfuse 20108000001 and 20108000021 be used interchangeably with the 5MT 800-R?

A: Yes. Both Littelfuse parts meet all core substitution criteria: 800 mA current rating, 250 V AC voltage rating, 5mm x 20mm package dimensions, glass cartridge type, medium blow response, and holder-based mounting. Both are active products with current manufacturing support.

Q: What is the difference between the Littelfuse 20108000001 and 20108000021?

A: Both parts are electrically and mechanically identical. They share the same current rating, voltage rating, package dimensions, response characteristics, and electrical parameters. The difference in part numbers reflects internal Littelfuse catalog organization. Either part is suitable for substitution.

Q: Are the Eaton GMC series parts (BK/GMC-800-R, BK1/GMC-800-R, GMC-800-R) interchangeable?

A: Yes. All three Eaton variants meet the core substitution criteria and are electrically equivalent. The BK1/GMC-800-R and BK/GMC-800-R are cross-referenced in the substitute list, indicating their interchangeability. GMC-800-R is also fully compatible.

Q: How do the Littelfuse and Eaton substitutes differ from the original 5MT 800-R?

A: The primary differences are melting I²t values and DC cold resistance. Littelfuse parts have lower melting I²t (1.1 vs. 3.8) and unspecified DC cold resistance. Eaton parts have the lowest melting I²t (0.85) and lower DC cold resistance (0.18 Ohms vs. 0.261 Ohms). These differences affect response speed and resistive heating but do not prevent substitution for applications designed around the 800 mA, 250 V specification.

Q: Does the operating temperature range difference affect substitution?

A: The Littelfuse parts operate from -25°C to 70°C, compared to the original -55°C to 125°C range. For applications operating within the -25°C to 70°C window, this difference is not relevant. Applications requiring operation below -25°C or above 70°C should account for this limitation or select alternatives with wider temperature specifications.

Q: What certifications should I consider for my application?

A: The original 5MT 800-R carries CE, CSA, and cULus certifications. Littelfuse substitutes carry cULus certification. Eaton substitutes carry CSA, UL, and KC certifications. Select the substitute whose certification profile aligns with your application's regulatory requirements and geographic market.

Q: Can I use these substitutes in existing 5MT 800-R fuse holders?

A: Yes. All substitute parts maintain the 5mm x 20mm package dimensions and holder-based mounting configuration, ensuring mechanical compatibility with existing 5MT 800-R fuse holders.