GMD-1A Equivalent & Substitute Parts Reference

Part Overview

The Eaton GMD-1A is a 1.25 A, 250 V AC/DC glass cartridge fuse in 5mm x 20mm form factor with slow blow response characteristics. This fuse requires a compatible holder for installation and is designed for circuit protection applications requiring slow blow response. The part is currently active in production with 703 pieces in stock. Equivalent and substitute parts are identified based on matching electrical ratings, mechanical dimensions, response time characteristics, and approval agency certifications to ensure functional interchangeability within specified parameters.

Key Parameters

Parameter	Value
Manufacturer Part Number	GMD-1A
Manufacturer	Eaton - Electronics Division
Series	GMD
Current Rating	1.25 A
Voltage Rating - AC	250 V
Fuse Type	Cartridge, Glass
Package / Case	5mm x 20mm
Response Time	Slow Blow
Mounting Type	Requires Holder
Size / Dimension	0.205" Dia x 0.787" L (5.20mm x 20.00mm)
RoHS Status	ROHS3 Compliant
Product Status	Active

Substitute Part Grouping Explanation

Substitute parts for the GMD-1A are grouped based on the following critical parameters that determine functional interchangeability:

Primary Matching Criteria:

Current Rating: 1.25 A
Voltage Rating - AC: 250 V
Fuse Type: Cartridge, Glass
Package / Case: 5mm x 20mm
Response Time: Slow Blow
Mounting Type: Requires Holder

Secondary Considerations:

Breaking Capacity @ Rated Voltage
Melting I²t characteristics
Approval Agency certifications (CSA, PSE/JET, UL, cULus, IMQ, VDE, BSI, CCC, SEMKO)
DC Cold Resistance
RoHS compliance status

Parts are considered equivalent when they maintain identical electrical ratings (1.25 A, 250 V AC), identical mechanical form factor (5mm x 20mm), and identical response time classification (Slow Blow). Variations in breaking capacity, melting I²t, and DC cold resistance are noted but do not preclude substitution when all primary criteria are met and approval certifications are appropriate for the application.

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating (A)	Voltage Rating - AC (V)	Response Time	Package / Case	Breaking Capacity @ Rated Voltage (A)	Melting I²t	DC Cold Resistance (Ohms)	Approval Agency	Inventory (Pcs)
GMD-1A	Eaton - Electronics Division	GMD	1.25	250	Slow Blow	5mm x 20mm	35	Not Specified	Not Specified	Not Specified	703
GMD-1-R	Eaton - Electronics Division	GMD	1	250	Slow Blow	5mm x 20mm	35	12	0.3065	CSA, PSE/JET, UL	853
BK/GDC-1.25A	Eaton - Electronics Division	GDC	1.25	250	Slow Blow	5mm x 20mm	35	10.05	0.06	cULus, IMQ, MITI/JET	1775
BK/GMD-1.25-R	Eaton - Electronics Division	GMD	1.25	250	Slow Blow	5mm x 20mm	100	16	0.1995	CSA, PSE/JET, UL	1115
BK/S506-1.25-R	Eaton - Electronics Division	S506	1.25	250	Slow Blow	5mm x 20mm	35	10.05	0.06	BSI, CCC, CSA, CURUS, IMQ, PSE/JET, SEMKO, VDE	2930
BK1/GMD-1.25-R	Eaton - Electronics Division	GMD	1.25	250	Slow Blow	5mm x 20mm	100	16	0.1995	CSA, PSE/JET, UL	1859
GDC-1.25A	Eaton - Electronics Division	GDC	1.25	250	Slow Blow	5mm x 20mm	35	10.05	0.06	cURus, IMQ, MITI/JET	975
GMD-1.25-R	Eaton - Electronics Division	GMD	1.25	250	Slow Blow	5mm x 20mm	100	16	0.1995	CSA, PSE/JET, UL	926
S506-1.25-R	Eaton - Electronics Division	S506	1.25	250	Slow Blow	5mm x 20mm	35	10.05	0.06	BSI, CCC, CSA, CURUS, IMQ, PSE/JET, SEMKO, VDE	624
0034.3118	SCHURTER Inc.	FST 5x20	1.25	250	Slow Blow	5mm x 20mm	35	5.5	Not Specified	CCC, cURus, PSE/JET, VDE	13782
0034.3776	SCHURTER Inc.	FSL 5x20	1.25	250	Slow Blow	5mm x 20mm	100	1.54	Not Specified	cULus	631

Engineering Selection Recommendations

Eaton GMD Series (Direct Manufacturer Match): GMD-1.25-R, BK/GMD-1.25-R, and BK1/GMD-1.25-R are direct series equivalents with identical current rating (1.25 A), voltage rating (250 V), and mechanical form factor. These parts carry CSA, PSE/JET, and UL certifications. Breaking capacity is rated at 100 A with melting I²t of 16. These are recommended for applications requiring GMD series continuity and North American certification compliance.

Eaton GDC Series (Parametric Equivalent): BK/GDC-1.25A and GDC-1.25A maintain identical electrical ratings and mechanical dimensions. These parts carry cULus, IMQ, and MITI/JET certifications. Breaking capacity is 35 A with melting I²t of 10.05. These are suitable for applications requiring international certification coverage.

Eaton S506 Series (Parametric Equivalent): BK/S506-1.25-R and S506-1.25-R provide the broadest certification coverage including BSI, CCC, CSA, CURUS, IMQ, PSE/JET, SEMKO, and VDE. Electrical and mechanical parameters match the main part. Breaking capacity is 35 A with melting I²t of 10.05. These are recommended for global applications requiring multi-region compliance.

SCHURTER FST 5x20 Series (0034.3118): This part maintains identical electrical ratings and mechanical form factor with CCC, cURus, PSE/JET, and VDE certifications. Melting I²t is 5.5. Operating temperature range is -55°C to 125°C. This part is suitable for applications requiring extended temperature performance.

SCHURTER FSL 5x20 Series (0034.3776): This part maintains identical electrical ratings and mechanical form factor with cULus certification. Breaking capacity is 100 A with melting I²t of 1.54. Operating temperature range is -40°C to 85°C. This part is suitable for applications requiring higher breaking capacity with cULus certification.

Current Rating Consideration: GMD-1-R is rated at 1 A, which is lower than the GMD-1A specification of 1.25 A. This part is not recommended as a direct substitute due to the current rating mismatch.

Frequently Asked Questions (FAQ)

Q: Can GMD-1.25-R be used as a direct replacement for GMD-1A?

A: Yes. GMD-1.25-R is a direct equivalent within the GMD series. Both parts are rated at 1.25 A, 250 V AC, with 5mm x 20mm form factor and slow blow response. Both require a compatible holder for installation. Certification differences should be verified against application requirements.

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

A: Breaking capacity indicates the maximum current the fuse can safely interrupt at rated voltage. Parts with 100 A breaking capacity (BK/GMD-1.25-R, BK1/GMD-1.25-R, GMD-1.25-R, 0034.3776) can handle higher fault currents than parts with 35 A breaking capacity. Selection depends on the maximum fault current expected in the application circuit.

Q: Are SCHURTER parts compatible with Eaton fuse holders?

A: SCHURTER 0034.3118 and 0034.3776 maintain identical 5mm x 20mm mechanical dimensions and cartridge glass fuse type as Eaton equivalents. Mechanical compatibility with standard 5mm x 20mm fuse holders is ensured. Electrical performance characteristics differ; verify melting I²t and breaking capacity against application requirements.

Q: What does melting I²t indicate?

A: Melting I²t is a thermal characteristic indicating the energy required to melt the fuse element. Lower values indicate faster response to overcurrent. Eaton parts range from 10.05 to 16, while SCHURTER FST 5x20 is 5.5 and FSL 5x20 is 1.54. Selection should match the circuit protection requirements.

Q: Which substitute part has the broadest international certification?

A: BK/S506-1.25-R and S506-1.25-R carry certifications from BSI, CCC, CSA, CURUS, IMQ, PSE/JET, SEMKO, and VDE, providing the widest geographic and regulatory compliance coverage among available substitutes.

Q: Can GMD-1-R replace GMD-1A?

A: No. GMD-1-R is rated at 1 A, while GMD-1A is rated at 1.25 A. The lower current rating makes GMD-1-R unsuitable as a direct replacement. Using an undersized fuse creates circuit protection inadequacy.

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

A: Eaton parts do not specify operating temperature ranges in provided data. SCHURTER 0034.3118 (FST 5x20) operates from -55°C to 125°C. SCHURTER 0034.3776 (FSL 5x20) operates from -40°C to 85°C. Verify temperature requirements against application environment.

Q: Are all substitute parts RoHS3 compliant?

A: Eaton parts (GMD-1.25-R, BK/GMD-1.25-R, BK1/GMD-1.25-R, GDC-1.25A, BK/GDC-1.25A, S506-1.25-R, BK/S506-1.25-R) are confirmed ROHS3 compliant. SCHURTER parts (0034.3118, 0034.3776) are confirmed ROHS3 compliant. All substitutes meet RoHS3 requirements.

Q: What is the difference in DC cold resistance between parts?

A: DC cold resistance varies among substitutes: Eaton GMD series parts range from 0.1995 to 0.3065 Ohms, while Eaton GDC and S506 series parts are 0.06 Ohms. SCHURTER parts do not specify DC cold resistance. Lower resistance reduces voltage drop across the fuse element during normal operation.

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