GMD-2.5A Glass Cartridge Fuse 1.25A 250VAC 5x20mm Equivalent & Substitute Parts

Part Overview

The GMD-2.5A is a 1.25 A, 250 V AC/DC glass cartridge fuse in 5mm x 20mm form factor manufactured by Eaton Electronics Division. This slow-blow fuse cartridge requires a holder for installation and is designed for circuit protection applications requiring slow response characteristics. The part is active in production with 1,135 pieces in current inventory stock. Equivalent and substitute parts are identified based on matching electrical ratings, mechanical dimensions, response time characteristics, and approval agency certifications.

Key Parameters

Parameter	Value
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

Substitute Part Grouping Explanation

Substitute parts for the GMD-2.5A are grouped based on strict equivalence of the following parameters:

Primary Equivalence 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

All identified substitute parts match these core electrical and mechanical parameters. Variations in secondary parameters such as Breaking Capacity, Melting I²t, DC Cold Resistance, and Approval Agency certifications are documented but do not disqualify substitution eligibility when primary parameters align.

Parameter Comparison

Part Number	Manufacturer	Series	Current Rating (A)	Voltage (V AC)	Response Time	Package	Breaking Capacity (A)	Melting I²t	DC Cold Resistance (Ohms)	Inventory (Pcs)
GMD-2.5A	Eaton	GMD	1.25	250	Slow Blow	5x20mm	100	16	0.1995	1,135
BK/GDC-1.25A	Eaton	GDC	1.25	250	Slow Blow	5x20mm	35	10.05	0.06	1,775
BK/GMD-1.25-R	Eaton	GMD	1.25	250	Slow Blow	5x20mm	100	16	0.1995	1,115
BK/S506-1.25-R	Eaton	S506	1.25	250	Slow Blow	5x20mm	35	10.05	0.06	2,930
BK1/GMD-1.25-R	Eaton	GMD	1.25	250	Slow Blow	5x20mm	100	16	0.1995	1,859
GDC-1.25A	Eaton	GDC	1.25	250	Slow Blow	5x20mm	35	10.05	0.06	975
GMD-1.25-R	Eaton	GMD	1.25	250	Slow Blow	5x20mm	100	16	0.1995	926
S506-1.25-R	Eaton	S506	1.25	250	Slow Blow	5x20mm	35	10.05	0.06	624
0034.3118	SCHURTER Inc.	FST 5x20	1.25	250	Slow Blow	5x20mm	35	5.5	Not Provided	13,782
0034.3776	SCHURTER Inc.	FSL 5x20	1.25	250	Slow Blow	5x20mm	100	1.54	Not Provided	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 electrical parameters and 100A breaking capacity. These parts carry CSA, PSE/JET, and UL certifications. Selection from this group is appropriate when the original GMD series specification is required.

Eaton GDC Series (Parametric Equivalent): BK/GDC-1.25A and GDC-1.25A match all primary electrical and mechanical parameters but feature 35A breaking capacity and different approval agencies (cULus, IMQ, MITI/JET). These parts are suitable for applications where the lower breaking capacity is acceptable and the specified certifications are sufficient.

Eaton S506 Series (Parametric Equivalent): BK/S506-1.25-R and S506-1.25-R provide the broadest approval agency coverage (BSI, CCC, CSA, CURUS, IMQ, PSE/JET, SEMKO, VDE) with 35A breaking capacity. These parts are appropriate for international applications requiring multiple regional certifications.

SCHURTER FST 5x20 Series (0034.3118): This part matches all primary electrical and mechanical parameters with 35A breaking capacity. It carries CCC, cURus, PSE/JET, and VDE certifications. Operating temperature range is specified as -55°C to 125°C. This part is suitable for applications requiring SCHURTER brand specification or when the specified certifications are required.

SCHURTER FSL 5x20 Series (0034.3776): This part matches all primary electrical and mechanical parameters with 100A breaking capacity. It carries cULus certification. Operating temperature range is specified as -40°C to 85°C. This part is suitable for applications requiring SCHURTER brand specification with higher breaking capacity.

Frequently Asked Questions (FAQ)

Q: What determines if a fuse can substitute for the GMD-2.5A?

A: Substitution is determined by matching the following parameters: 1.25 A current rating, 250 V AC voltage rating, slow-blow response time, 5mm x 20mm physical dimensions, glass cartridge type, and holder-mount configuration. All identified substitute parts meet these criteria.

Q: Are there differences in breaking capacity among the substitute parts?

A: Yes. The GMD-2.5A and certain substitutes (BK/GMD-1.25-R, BK1/GMD-1.25-R, GMD-1.25-R, 0034.3776) feature 100A breaking capacity. Other substitutes (BK/GDC-1.25A, GDC-1.25A, BK/S506-1.25-R, S506-1.25-R, 0034.3118) feature 35A breaking capacity. Breaking capacity selection depends on application requirements and circuit protection specifications.

Q: Do all substitute parts have the same approval certifications?

A: No. Approval agencies vary by part. The GMD series carries CSA, PSE/JET, and UL certifications. The GDC series carries cULus, IMQ, and MITI/JET certifications. The S506 series carries the broadest coverage: BSI, CCC, CSA, CURUS, IMQ, PSE/JET, SEMKO, and VDE. SCHURTER parts carry different certification combinations. Selection should align with application certification requirements.

Q: Can I use a SCHURTER fuse in place of an Eaton fuse?

A: Yes, provided the electrical parameters (1.25 A, 250 V AC, slow-blow, 5x20mm) and required certifications match. SCHURTER 0034.3118 and 0034.3776 meet the electrical equivalence criteria. Verify that the application's certification requirements are satisfied by the SCHURTER part's approval agencies.

Q: What is the difference between Melting I²t values in the substitute parts?

A: Melting I²t is a thermal characteristic that affects fuse response speed. Lower values indicate faster thermal response. The GMD-2.5A has a Melting I²t of 16. Substitutes range from 1.54 (0034.3776) to 10.05 (GDC and S506 series). All parts are classified as slow-blow, but the thermal response varies. Application thermal requirements should determine acceptable Melting I²t ranges.

Q: Is the 5mm x 20mm dimension critical for substitution?

A: Yes. The 5mm x 20mm dimension is the physical form factor that determines holder compatibility. All substitute parts maintain this exact dimension (0.205" Dia x 0.787" L). Substitution outside this dimension would require holder replacement and is not covered by this equivalence list.

Q: What does "Requires Holder" mean?

A: This fuse type is a cartridge fuse that must be installed in a dedicated fuse holder. It is not a plug-type fuse. The holder provides electrical contact and mechanical retention. All substitute parts require the same holder type.

Q: Can I substitute based on DC Cold Resistance values?

A: DC Cold Resistance is a measured characteristic but is not a primary substitution criterion. The GMD-2.5A has 0.1995 Ohms. GDC and S506 series have 0.06 Ohms. SCHURTER parts do not provide this specification. Substitution is based on electrical ratings and mechanical dimensions, not resistance values.

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