Mersen OT1 Amp-Trap Class K5 F...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$55.06
$6.79
Mersen OT1 Fuse Amp-Trap 250V 1A Fast-Acting Class K5 OT Series

Mersen OT1 Amp-Trap Class K5 Fast-Acting Fuse, 250V 1A

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Model: OT1

In Stock (leaves warehouse same day if ordered before 3pm ET)

$55.06
$6.79
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Mersen OT1 Amp-Trap Class K5 Fast-Acting Fuse, 250V 1A

The Mersen OT1 is a 250V, 1A fast-acting Class K5 fuse from the Amp-Trap OT Series, built for reliable overcurrent protection in feeders, resistive heating circuits, and branch circuits. Rated for a 50 kA AC breaking capacity and self-certified for DC use per UL248, this OT1 fuse pairs a compact 2 in length with an easy-to-read imprint label for quick recognition and replacement, delivering high protection value at low cost for residential and small commercial installations.

Key Features

  • Trade Size: 2 in length by 0.56 in diameter for standard fuse clip mounting.
  • Durable Construction: Paper body insulating material provides reliable dielectric protection within the fuse body.
  • Terminal Connection: Ferrule-style copper connection terminals for secure, low-resistance contact in fuse clips.
  • Mounting Method: Clip-mounted for straightforward installation and replacement in standard fuse holders.
  • Electrical Rating: 250V AC/DC rated, 1A fast-acting Class K5 fuse with a 50 kA AC maximum breaking capacity.
  • Easy Identification: Easy-to-read imprint label speeds up recognition and replacement in the field.
  • Value: Low-cost design delivers high protection value for feeders, resistive heating, and branch circuit applications.

Certifications & Compliance

  • UL Listed to Standard 248-9, File E2137
  • CSA Certified to Standard C22.2 No. 248.9
  • Self-certified for DC per UL248

Technical Specifications

  • AC Max Breaking Capacity: 50 kA
  • Amperage Rating: 1A
  • Body Insulating Material: Paper
  • Connection Terminal Material: Copper
  • Connection Terminal Type: Ferrule
  • Mounting Method: Clip
  • Product Diameter: 0.56 in
  • Product Length: 2 in
  • Product Weight: 0.04 lb
  • Rated Voltage AC (UL): 250 V
  • Rated Voltage DC (UL): 250 V
  • Sell Pack Quantity: 10 Each

Typical Applications

  • Feeders
  • Resistive Heating Circuits
  • Branch Circuits
  • Residential and Small Commercial Installations
  • Overcurrent Protection for Electrical Panels

Why Mersen?

Mersen's OT1 Amp-Trap fuse combines UL Listed and CSA Certified performance with a paper-insulated body, copper ferrule terminals, and a 50 kA AC breaking capacity for dependable, code-compliant overcurrent protection. The easy-to-read imprint label and clip-mount design make identification and replacement fast for professionals working on feeders, branch circuits, and resistive heating applications.

Product Specs

AC Max I.R./Breaking Capacity: I1:
50 kA
Ampere Rating:
1 A
Body/Insulating Material:
Paper
Connection/Terminal Material:
Copper
Connection Terminal Type:
Ferrule
Fuse Class:
Class K5
Mounting Method:
Clip
Product Diameter:
0.56 in
Product Length:
2 in
Product Weight:
0.04 lb
Rated voltage AC UL:
250 V
Rated voltage DC UL:
250 V
Sell Pack Height:
1.19 in
Sell Pack Length:
3 in
Sell Pack Quantity:
10 Each
Sell Pack Weight:
0.42 lb
Sell Pack Width:
2.06 in
Speed/Characteristic:
Fast-Acting
Department:
Electrical
Product Group:
Circuit Protection
Product Type:
Fast-Acting Fuse
Product Subgroup:
Fuses

Mersen OT1 – Frequently Asked Questions

1) Will the Mersen OT1 fuse fit standard fuse clips in my panel or fuse block?
The OT1 is a 2 inch long, 0.56 inch diameter ferrule fuse that drops into standard clip-type holders sized for that body. Terminals are copper ferrules, so contact resistance stays low in the clips. That 2 x 0.56 inch envelope is the classic one-time Class H/K5 cartridge size for ratings up to 30A, so if the holder currently carries a 250V ferrule cartridge of the same dimensions, the OT1 seats the same way.
2) Can I use the Mersen OT1 on a DC circuit, or is it AC only?
Both. The OT1 carries a 250 V AC rating and a 250 V DC rating under UL, and Mersen self-certifies the DC use per UL248. Interrupting rating of 50 kA is the AC figure.
3) Is a Class K5 fast-acting fuse the right choice for a motor circuit?
No. The OT1 is fast-acting, so it clears overcurrent quickly with no intentional time delay and will nuisance-open on motor inrush. It suits feeders, resistive heating loads, and branch circuits with non-inductive loads. For a motor or transformer you want a time-delay fuse instead, such as the Littelfuse CCMR Series Class CC time-delay (CCMR040 is the 40A version).
4) Is the Mersen OT1 UL Listed and CSA certified for a commercial install?
Yes. The OT1 is UL Listed to Standard 248-9 under File E2137 and CSA Certified to C22.2 No. 248.9. That is the Class K fuse standard, which is what an inspector will look for on a 250V branch or feeder application.
5) My panel is 480V. Can I use the Mersen OT1?
No. The OT1 is rated 250 V AC and 250 V DC and must not be applied above that. For a 480V circuit you need a 600V class fuse. Using a 250V fuse on a higher system voltage risks the fuse failing to clear the arc.
6) What is the closest alternative to the Mersen OT1 for a 250V fast-acting midget-style fuse?
The Littelfuse BLF series is a midget fast-acting fuse rated 250V with a laminated tube body, which puts it in the same fast-acting 250V territory as the Mersen OT1. The OT1 itself is a Class K5 fast-acting fuse rated 250V AC and 250V DC at 1A, 2 in long by 0.56 in diameter, with copper ferrule terminals for clip mounting. The BLF is a midget-dimension fuse, so confirm your fuse clip spacing and the ampere rating you need before substituting.
7) If the circuit needs time-delay rather than fast-acting protection, what should be used instead of the Mersen OT1?
The Mersen OT1 is a fast-acting Class K5 fuse, so it clears overcurrent without an intentional delay and is not suited to loads with high inrush such as motors or transformers. For a time-delay characteristic, the Littelfuse CCMR040 is a Class CC time-delay fuse rated 40A. Note that Class CC and Class K5 are different fuse classes with different holder and rejection requirements, so the CCMR040 is a design change rather than a drop-in for an OT1 clip.
8) Is the Mersen OT1 a renewable fuse or a one-time fuse?
It is a one-time, non-renewable cartridge. The body is paper insulated with fixed copper ferrule ends, so once it opens it gets pulled and replaced, not re-linked. Buyers stocking a panel usually keep spares on the shelf for that reason.
9) How many Mersen OT1 fuses come in a pack?
The OT1 sells in a pack of 10. The carton runs 3 x 2.06 x 1.19 inches and weighs 0.42 lb, with each fuse at 0.04 lb, so it is easy to keep a box in a service van or on an MRO shelf.
10) What is the difference between the Mersen OT1 and a glass tube fuse like the Littelfuse AGU or AGA?
Different jobs. The OT1 is a 250V Class K5 power fuse with a paper body, copper ferrules, and a 50 kA interrupting rating, meant for panel feeders and branch circuits. The Littelfuse AGA Series (AGA5 is the 5A) and AGU Series are glass tube fuses, which are typically used in equipment and automotive or appliance circuits, not in distribution fuse blocks with high available fault current.
11) Will a 1 amp Mersen OT1 handle the available fault current in my service panel?
The OT1 has a 50 kA AC maximum breaking capacity, which covers most residential and small commercial services. Check the available fault current at the point of application against that figure; if the calculated fault current at the panel exceeds 50 kA, this Class K5 fuse is not the right device.
12) Can a Littelfuse AGA or AGU glass fuse be used in place of the Mersen OT1?
They serve different roles. The Littelfuse AGA5 is a 5A glass fuse in the AGA series and the AGU is an AG glass tube fuse, both small glass-tube types typically used in equipment and automotive-style holders. The Mersen OT1 is a Class K5 branch-circuit fuse rated 250V AC and 250V DC with a 50 kA AC maximum breaking capacity, a paper insulating body and copper ferrule terminals for clip mounting in a panel. For feeder, branch circuit and resistive heating protection, stay with the K5 fuse rather than a glass tube.
13) Is the Square D PowerLogic energy meter fuse pack an alternative to the Mersen OT1 for metering circuits?
The Square D PowerLogic fuse pack is a set of three fuses rated 0.5A at 600V, intended for energy meter voltage sensing. The Mersen OT1 is a single 1A fuse rated 250V AC and 250V DC. If your metering circuit sits on a 480V or 600V system, the 250V OT1 is not the right voltage class; if it is a 240V circuit needing 1A branch protection, the OT1 applies and the 0.5A meter pack does not.
14) How do I choose between the Mersen OT1 and the Littelfuse BLF for a 250V control or heating circuit?
Both are fast-acting 250V fuses. The Mersen OT1 is Class K5 at 1A with a 50 kA AC breaking capacity, a 2 in by 0.56 in body and copper ferrule terminals for clip mounting, and ships 10 per pack. The Littelfuse BLF is a midget-style fast-acting 250V fuse with a laminated tube body. The deciding factors are the holder you already have in the panel and the available fault current at that point in the system, since midget and K5 dimensions differ.
15) What part number do I order for the 1 amp 250V Mersen Amp-Trap OT fuse?
Order Mersen OT1. That is the 1 amp, 250V fast-acting Class K5 unit in the Amp-Trap OT Series, and the ampere rating is what the part number suffix carries.
How fast can I get the Mersen OT1 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Mersen OT1 come with a warranty?
Absolutely. The Mersen OT1 is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Mersen OT1?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
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