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Mersen GSF Series Time-Delay Ceramic Ferrule Fuse
The Mersen GSF Series is a time-delay miniature fuse built with a ceramic body in the 5mm x 20mm (5x20) size, designed to protect sensitive electronic and electrical circuits from inrush current surges while still responding to sustained overloads. Rated 250VAC and 2.5A, this AC-rated fuse uses a ferrule terminal design for clip mounting, making it a reliable supplemental-class overcurrent protection device for equipment where brief current spikes are normal but sustained faults must be cleared. Its ceramic insulating body adds thermal and mechanical durability compared to glass-body alternatives, and the fuse is RoHS compliant for use in environmentally regulated electronic assemblies.
Key Features
- Fuse Size: 5mm x 20mm (5x20) miniature format for compact fuse holders and clip mounts.
- Ceramic Body Construction: Ceramic insulating material provides added heat and mechanical durability versus glass-body fuses.
- Ferrule Terminal, Clip Mounting: Ferrule connection/terminal type installs securely into standard clip-style fuse holders.
- Time-Delay Characteristic: Time-delay (slow-blow) speed rating allows momentary inrush current without nuisance tripping.
- Ampere Rating: 2.5A rated current for precise circuit-level overcurrent protection.
- Voltage Rating: 250V AC rated voltage (AC or DC: AC) suitable for standard AC-powered equipment.
- Fuse Class: Supplemental fuse class intended for internal appliance and equipment protection.
Certifications & Compliance
- RoHS Compliant
Technical Specifications
- AC or DC: AC
- ROHS Compliant: Yes
Typical Applications
- Electronic Equipment and Control Circuit Protection
- Industrial Control Panels and Devices
- Power Supplies and Instrumentation
- Appliance and Equipment Internal Circuit Protection
- OEM Assemblies Requiring Time-Delay Overcurrent Protection
Why Mersen?
Mersen's GSF Series pairs a durable ceramic body with a time-delay characteristic engineered to distinguish harmless inrush current from genuine overload conditions, helping protect connected equipment without unnecessary interruptions. With a 250VAC, 2.5A rating, ferrule terminals for secure clip mounting, and RoHS-compliant construction, this fuse is built for dependable, code-conscious performance in professional and OEM electrical applications where consistent supplemental overcurrent protection matters.
Manufacturer Resources
Mersen Product Catalog
Product Specs
- list_batch:
- MERSEN-20260825
- Product Type:
- Time-Delay Fuse
- Product Material:
- Ceramic
- Connection Type:
- Ferrule
- Voltage Rating:
- 250V
- Amperage Rating:
- 2.5A
- Series:
- GSF
- Standards:
- RoHS
- Department:
- Electrical
- Product Group:
- Circuit Protection
- Product Subgroup:
- Fuses
Mersen GSF2-1/2 – Frequently Asked Questions
1) Will the Mersen GSF2-1/2 fuse fit a standard 5x20mm fuse holder?
Yes. The GSF Series is built in the 5mm x 20mm miniature format with ferrule terminals, so it drops into standard 5x20 clip-style holders and panel-mount fuse carriers. The ferrule ends are the plain cylindrical caps those clips grip, so no lead forming or soldering is involved.
2) Is the Mersen GSF 2.5A fuse slow-blow or fast-acting?
Time-delay, also called slow-blow. It rides through the brief inrush a transformer, motor or switching power supply draws at startup, then still opens on a sustained overload. If your circuit is nuisance-blowing a fast-acting fuse at power-up, this is the characteristic you want. If you are protecting semiconductors that need the fastest possible clearing, a fast-acting type such as the Littelfuse BLF Series midget fuse is the other direction.
3) Is this Mersen fuse suitable for branch circuit protection in a panel?
No. The GSF is a supplemental-class fuse, meant for protecting circuits inside equipment: control circuits, power supplies, instrumentation and appliance internals downstream of a branch circuit device. It is not a branch circuit protective device. For branch circuit duty in a panel you want a Class CC or similar listed fuse, such as the Littelfuse CCMR Series Class CC time-delay fuse.
4) Can I drop this in where a 2.5A glass 5x20 fuse keeps blowing on startup?
If the old fuse was fast-acting and the circuit has normal inrush, yes, the GSF2-1/2 is the same 5x20 ferrule envelope at the same 2.5A and 250V AC, with a time-delay characteristic that tolerates the startup surge. If the existing fuse was already time-delay at 2.5A and still opening, you have a real fault or an undersized rating, not a fuse type problem.
5) What is the difference between the Mersen GSF2-1/2 and the Littelfuse BLF series fuse?
The Mersen GSF2-1/2 is a time-delay ceramic-body fuse rated 2.5A at 250V with ferrule terminals for clip mounting. The Littelfuse BLF series is a midget fast-acting fuse rated 250V in a laminated tube body. Both share the 250V class, but the operating characteristic is opposite: the GSF tolerates momentary inrush before clearing, while the BLF is fast-acting and intended to open quickly on overcurrent. Choose the GSF where motor, transformer, or power-supply inrush would nuisance-trip a fast-acting element, and the BLF where the circuit needs the quickest possible clearing.
6) If I need a time-delay fuse for a larger branch circuit than the Mersen GSF2-1/2 covers, what should I use instead?
The Mersen GSF2-1/2 is a 2.5A supplemental-class miniature fuse in the 5mm x 20mm ferrule format, sized for internal equipment and control circuit protection rather than branch-circuit duty. For a branch circuit at higher current, the Littelfuse CCMR040 is a Class CC time-delay fuse rated 40A, which uses a rejection-style midget body rather than a 5x20 clip holder. The two are not interchangeable in the same holder - the CCMR requires a Class CC fuse block, while the GSF drops into standard 5x20 clips.
7) What is the difference between a ceramic fuse and a glass fuse of the same size?
The GSF uses a ceramic insulating body instead of glass. Ceramic adds heat and mechanical durability, which matters inside a hot control panel or a vibrating machine enclosure. The tradeoff is that you cannot see the element, so you cannot tell by eye whether it has opened, you have to meter it. Glass-body alternatives we carry include the Littelfuse AGA and AGU Series tube fuses if visual inspection is the priority.
8) What exact part number do I order for the 2.5 amp Mersen GSF fuse?
The 2.5A version is Mersen part GSF2-1/2, rated 250V AC in the 5x20 ceramic ferrule body. Mersen writes the fractional amperage into the number, so GSF2-1/2 means two and a half amps, not a dash-two variant.
9) Can I substitute a Littelfuse AGA or AGU glass fuse for the Mersen GSF2-1/2?
Not as a direct equivalent. The Mersen GSF2-1/2 uses a ceramic insulating body, which adds thermal and mechanical durability over glass-body construction, and carries a 2.5A 250V time-delay rating. The Littelfuse AGA5 is a 5A glass fuse and the Littelfuse AGU is a glass tube fuse in the AG family - different body material, different physical size family, and in the AGA5 case a different ampere rating. Only consider a glass AG-series fuse where the holder and the equipment's fuse specification actually call for that size and rating.
10) We need fuses for a PowerLogic energy meter - will the Mersen GSF2-1/2 work?
Use the metering fuse specified for the instrument. The Square D PowerLogic energy meter fuse pack is a set of three rated 0.5A at 600V, matched to meter voltage-sensing leads. The Mersen GSF2-1/2 is rated 2.5A at 250V, so it is both a higher ampere rating and a lower voltage rating than a 600V metering application requires. The GSF belongs in equipment and control circuits at 250V or less where time-delay response to inrush is wanted.
11) Does the Mersen GSF fuse meet RoHS for electronic assemblies we export?
Yes, the GSF Series is RoHS compliant, which is what OEMs building into regulated electronic assemblies need on the bill of materials.
12) For an OEM assembly that has to meet RoHS, how does the Mersen GSF compare to other fuse options?
The Mersen GSF2-1/2 is documented as RoHS compliant, which is the reason it is commonly specified for electronic assemblies built to environmental compliance requirements, along with its ceramic body and 5x20 ferrule format for clip-mounted holders. Among the alternatives, the Littelfuse CCMR040 is a Class CC time-delay fuse for panel fuse blocks and the Littelfuse BLF is a midget fast-acting fuse - both are larger panel-level formats rather than board or holder-level supplemental protection, so they address a different part of the assembly.
How fast can I get the Mersen GSF2-1/2 delivered?
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Does the Mersen GSF2-1/2 come with a warranty?
Absolutely. The Mersen GSF2-1/2 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
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