Mersen OT Series Class K5 Fast...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$9.13
Mersen OT Series Class K5 Fast-Acting Fuse, 250VAC/250VDC

Mersen OT Series Class K5 Fast-Acting Fuse, 250VAC/250VDC

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Model: OT2

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

$9.13
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Mersen OT7 Class K5 Fast-Acting Fuse, 7A 250VAC/250VDC

The Mersen OT7 Class K5 Fast-Acting Fuse (Amp-Trap) delivers reliable overcurrent protection for circuits operating at 250VAC/250VDC with a 7A current rating. This professional-grade fuse features copper ferrule terminal connections, clip mounting, and paper body insulation, backed by a 50kA breaking capacity for safe fault current interruption in demanding electrical environments. RoHS compliant construction supports responsible component selection for industrial and commercial installations.

Key Features

  • 7A Current Rating: Provides precise overcurrent protection for circuits requiring 7-ampere capacity with reliable, repeatable performance.
  • 250VAC/250VDC Dual Voltage: Versatile voltage compatibility supports both AC and DC applications up to 250 volts for flexible installation across equipment types.
  • Class K5 Fast-Acting: Delivers rapid response to overcurrent conditions, minimizing potential damage to downstream equipment and circuits.
  • 50kA Breaking Capacity: High interrupting rating (Ac Max I R Breaking Capacity I1) ensures safe fault current interruption in demanding electrical environments.
  • Ferrule Terminal Design: Copper ferrule terminals provide secure, reliable connections with clip mounting for professional installation.
  • Paper Body Insulation: Traditional paper insulating material offers proven performance and reliability in fuse construction.
  • 50/60 Hz Frequency: Rated for standard AC frequencies, supporting compatibility with common industrial and commercial power systems.
  • Compact Footprint: 2 in product length and 0.029 lb weight suit space-constrained panel and enclosure layouts.

Certifications & Compliance

  • RoHS Compliant

Technical Specifications

  • Ac Max I R Breaking Capacity I1: 50 kA
  • Ac Or Dc: AC/DC
  • Ampere Rating: 7A
  • Body Insulating Material: Paper
  • Connection Terminal Material: Copper
  • Connection Terminal Type: Ferrule
  • Frequency Hz: 50/60 Hz
  • Fuse Class: Class K5
  • Mounting Method: Clip
  • Product Length: 2 in
  • Product Weight: 0.029 lb
  • Rated Voltage Ac Ul: 250 V
  • Rated Voltage Dc Ul: 250 V
  • Rohs Compliant: Yes
  • Speed Characteristic: Fast-Acting

Typical Applications

  • Industrial Control Panels
  • Motor Control Centers
  • Power Distribution Equipment
  • Commercial Electrical Systems
  • Manufacturing Facilities
  • Process Control Applications

Why Mersen?

Mersen delivers proven reliability in electrical protection with RoHS compliant construction and professional-grade materials. The copper ferrule terminals, paper body insulation, and 50kA breaking capacity work together to ensure dependable, code-compliant performance in demanding industrial and commercial electrical environments.

Manufacturer Resources

Mersen Product Catalog

Product Specs

Fuse Class:
Class K5
AC Max I.R./Breaking Capacity: I1:
50 kA
Product Type:
Fast-Acting Fuse
Frequency (Hz):
50/60 Hz
AC or DC:
AC/DC
Rated voltage DC UL:
250 V
Rated voltage AC UL:
250 V
Product Group:
Circuit Protection
Rohs Compliant:
Yes
Department:
Electrical
Speed/Characteristic:
Fast-Acting
Mounting Method:
Clip
Product Subgroup:
Fuses

Mersen OT2 – Frequently Asked Questions

1) What amp ratings does the Mersen OT Class K5 fuse come in?
The Mersen OT Amp-Trap series runs from 2A up to 150A: OT2, OT3, OT5, OT6, OT7, OT8, OT10, OT15, OT30, OT40, OT60, OT100, OT125 and OT150. Order by amp rating and the model number follows the rating directly, so a 30 amp circuit takes the OT30. Every rating in the series shares the same 250VAC/250VDC rating and Class K5 fast-acting characteristic, so stepping up or down in amperage doesn't change the voltage or speed behavior of the panel.
2) Can I use a Mersen OT fuse on a DC circuit, or is it AC only?
Both. The OT series carries a UL rated voltage of 250 V on AC and 250 V on DC, so it can sit in a 250VDC control or battery circuit as well as a 120/240V AC panel. On AC it is rated for 50/60 Hz, which covers standard North American and 50 Hz plant power. What it will not do is go above 250 volts on either side, so a 480V panel needs a different class of fuse entirely.
3) Will a Class K5 fast-acting fuse hold on a motor start, or will it blow every time?
Fast-acting is the wrong characteristic for a motor. The OT series is a Class K5 fast-acting fuse, which means it clears an overcurrent quickly with no intentional time delay, so a motor's locked-rotor inrush is likely to open it on startup. Use it where the load is resistive or electronic and you want the fastest possible clearing: control circuits, distribution feeds without heavy inrush, and equipment where a slow clear would cook the downstream components. If the load has inrush, you want a time-delay (dual-element) fuse instead, sized for the running current.
4) Is a Class K5 fuse the same as a Class H or Class RK5 fuse, and will it drop into the same clips?
Class K5 is a ferrule and blade fuse dimensionally interchangeable with Class H of the same amp and voltage rating, so it mounts in the same fuse clips. The difference is interrupting rating: the OT series is rated 50 kA, where a standard Class H is only rated 10 kA. What Class K5 does NOT have is the rejection feature of Class R, so it will fit a plain clip but it will not seat in a rejection-style Class R fuseholder. If your holder has the rejection pin or slot, you need an RK5 or RK1 fuse, not a K5.
5) My panel has an OT7 in it that keeps blowing. Should I put in a bigger amp fuse?
No. A fuse that opens repeatedly is reporting a problem, not a sizing error, and the OT series jumps 7A, 8A, 10A, 15A for a reason: the rating is chosen to protect the conductor and the equipment behind it. Going up a size on the same clips defeats that protection and can leave the wire unprotected. Replace like for like with another OT7 and find the fault. If the fuse is opening on startup rather than under load, the issue is that Class K5 is fast-acting with no time delay, and the circuit may need a time-delay fuse of the same rating instead.
6) Can I use a Square D PowerLogic energy meter fuse pack in place of a Mersen OT fuse?
No, they are built for different jobs. The Mersen OT is a Class K5 fast-acting fuse rated 250VAC/250VDC with a 50kA breaking capacity, sold by amperage from OT2 at 2A up through OT150 at 150A for branch and feeder protection in control panels and motor control centers. The Square D PowerLogic Energy Meter Fuse Pack is a set of three 0.5A 600V fuses intended for the voltage-sensing leads of a PowerLogic energy meter. The 600V rating and the half-amp element put it outside anything the OT range covers, and the OT range does not go low enough to protect a metering input.
7) What fuse do I use for the voltage-sensing leads on a PowerLogic energy meter if the smallest Mersen OT is 2A?
Go to the Square D PowerLogic Energy Meter Fuse Pack, which is a set of three 0.5A 600V fuses matched to PowerLogic metering inputs. The Mersen OT range starts at OT2 at 2A and is rated 250VAC/250VDC, so its lowest amperage is still well above what a meter voltage lead calls for and its voltage rating is below a 600V metering circuit. Order the OT series for the load side protection in the panel and the PowerLogic pack for the meter leads themselves.
8) What is the interrupting rating on the Mersen OT fuse, and is 50kA enough for my service?
50 kA AC. That is the maximum fault current the OT fuse can safely interrupt, and it covers the great majority of 240V commercial and industrial services, where available fault current at the panel is usually well under that figure. The number matters for your equipment's short circuit current rating: a panel marked for a given SCCR needs protective devices rated at or above the available fault current at that point. If your utility or engineer has given you an available fault current above 50 kA at the fuse location, this is not the right fuse.
9) How does the Mersen OT fuse mount, and do I need a block or does it clip in?
Clip mounting with ferrule ends. The OT fuse has copper ferrule terminals on each end and drops into standard fuse clips or a clip-style fuseholder, not a bolt-down or screw terminal. That means you need the holder or clip set sized for the fuse's ferrule diameter and length, which changes as the amp rating goes up. On the smaller ratings the body runs 2 inches long. If you are replacing an existing fuse, pull the old one and match the physical size before ordering, because a 30A body and a 100A body in this family are not the same size.
10) I need a small fuse for a power meter, not a distribution panel. Is the OT series right?
Probably not, if the meter has its own fuse spec. The Mersen OT series starts at 2A and is rated 250V, which is built for control panels, motor control centers, and distribution equipment. Metering circuits on higher-voltage systems usually call for a small 600V fuse instead. For example the Square D PowerLogic Energy Meter Fuse Pack is a 0.5A 600V set of three made for exactly that job. Match the fuse to what the meter manufacturer calls out rather than the nearest amp rating you can find.
11) Are Mersen OT fuses RoHS compliant for a spec that requires it?
Yes, the OT Amp-Trap fuses are RoHS compliant, which covers the restricted-substance requirement that shows up in institutional, healthcare, and export-bound equipment specs. That applies across the amp range from OT2 through OT150, so standardizing a facility on this series doesn't leave you with mixed compliance between panels.
How fast can I get the Mersen OT2 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 OT2 come with a warranty?
Absolutely. The Mersen OT2 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 OT2?
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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