Mersen TR1-1/8R Class RK5 Time-Delay Ferrule Fuse, 1.125A
The Mersen TR1-1/8R is a Tri-Onic Class RK5 time-delay fuse rated 1.125A at 250VAC/250VDC, built with a ferrule-style body and clip mounting for reliable installation in standard fuse holders. This time-delay design rides through momentary inrush and surge currents without nuisance tripping, making it well suited for motor branch circuits and general power distribution equipment. Backed by a 200 kA AC maximum breaking capacity and RoHS-compliant construction, this listing is supplied as a 100-pack for stocking and maintenance programs.
Key Features
- Ampere Rating: 1.125A rating delivers precise overcurrent protection for the intended circuit.
- Time-Delay Characteristic: Class RK5 time-delay performance absorbs temporary inrush and surge currents while still protecting against sustained overloads.
- Dual Voltage Rating: Rated 250VAC / 250VDC at 50/60 Hz for use across AC or DC circuits.
- Ferrule Terminals: Copper connection terminals paired with clip mounting for a secure, low-resistance connection.
- High Breaking Capacity: 200 kA AC maximum interrupting rating supports protection in high fault-current applications.
- PolyTube Body: Durable PolyTube insulating body material for consistent electrical isolation.
- Compact Footprint: Measures 2 in in length and weighs just 0.037 lb per fuse.
- Bulk Packaging: Supplied 100 per pack for facilities that stock replacement fuses in volume.
Certifications & Compliance
- RoHS Compliant
Technical Specifications
- Ac Max I R Breaking Capacity I1: 200 kA
- Ac Or Dc: AC/DC
- Ampere Rating: 1.125 A
- Body Insulating Material: PolyTube
- Connection Terminal Material: Copper
- Frequency Hz: 50/60 Hz
- Mounting Method: Clip
- Product Length: 2 in
- Product Weight: 0.037 lb
- Rated Voltage Ac Ul: 250 V
- Rated Voltage Dc Ul: 250 V
- Rohs Compliant: Yes
- Speed Characteristic: Time Delay
Typical Applications
- Motor Branch Circuit Protection
- Industrial Control Panels
- Panelboard and Load Center Fuse Replacement
- General Power Distribution Equipment
- OEM Equipment Requiring RK5 Time-Delay Fuses
Why Mersen?
Mersen's Tri-Onic Class RK5 fuses combine a copper-terminal, PolyTube-insulated construction with a 200 kA breaking capacity to deliver dependable, code-compliant overcurrent protection for demanding electrical systems. The time-delay characteristic and dual 250VAC/250VDC rating give installers flexibility across AC and DC applications, while RoHS-compliant materials support modern equipment specifications. Choose Mersen for consistent, professional-grade fuse performance backed by proven ferrule fuse design.
Manufacturer Resources
Mersen Product Catalog
Product Specs
- Ac Max I R Breaking Capacity I1:
- 200 kA
- Ac Or Dc:
- AC/DC
- Ampere Rating:
- 1.125 A
- Body Insulating Material:
- PolyTube
- Connection Terminal Material:
- Copper
- Connection Terminal Type:
- Ferrule
- Frequency Hz:
- 50/60 Hz
- Fuse Class:
- Class RK5
- Mounting Method:
- Clip
- Product Length:
- 2 in
- Product Weight:
- 0.037 lb
- Rated Voltage Ac Ul:
- 250 V
- Rated Voltage Dc Ul:
- 250 V
- Rohs Compliant:
- Yes
- Speed Characteristic:
- Time Delay
- Department:
- Electrical
- Product Group:
- Wiring Devices
- Product Type:
- Fuse
- Product Subgroup:
- Fuses by Type
Mersen TR1-1/8R – Frequently Asked Questions
1) Will a Mersen TR1-1/8R fit a standard 250V fuse block, or do I need a special holder?
The TR1-1/8R is a ferrule fuse with clip mounting, 2 inches long, so it drops into standard 250V clip-style fuse blocks and holders sized for Class RK5 ferrule fuses. There are no bolt-on tags to deal with, and the copper terminals give a low-resistance seat in the clips.
2) Can I use the Mersen TR1-1/8R on a DC circuit as well as AC?
Yes. The TR1-1/8R carries a 250V AC and 250V DC rating, at 50/60 Hz on the AC side, so it can be applied on either. The 200 kA AC maximum breaking capacity is the AC interrupting figure.
3) Why would I pick a time-delay RK5 fuse instead of a fast-acting one for a motor circuit?
Motor starting draws a large inrush for a short time. A fast-acting fuse sees that as a fault and opens. The TR1-1/8R has a time-delay characteristic, so it rides through the inrush and still opens on a sustained overload, which is why it suits motor branch circuits and control panels. For semiconductor or purely resistive loads where you want the fastest clearing, a fast-acting midget like the Littelfuse BLF Series is the other direction to look.
4) Can I use a Littelfuse BLF midget fuse in place of the Mersen TR1-1/8R?
Not as a direct equivalent. The Littelfuse BLF is a midget fast-acting fuse rated 250 V in a laminated tube body, while the Mersen TR1-1/8R is a Class RK5 time-delay fuse with a PolyTube body rated 250 VAC and 250 VDC. The fast-acting element will clear on the momentary inrush that a time-delay RK5 is chosen to ride through, so on a motor branch circuit or a control panel with transformer inrush the BLF is the wrong characteristic. Choose the BLF only where the circuit calls for fast-acting protection in a midget-size holder.
5) What is the difference between the Mersen TR1-1/8R and the Littelfuse CCMR040 time-delay fuse?
Both are time-delay fuses, but they are different classes and different amp ratings. The Mersen TR1-1/8R is a Class RK5 time-delay ferrule fuse rated 1.125 A at 250 VAC and 250 VDC, 2 in long, with copper ferrule terminals and clip mounting. The Littelfuse CCMR040 is a CCMR series Class CC time-delay fuse rated 40 A. Class CC and Class RK5 use different holder and block dimensions, so the two are not interchangeable in the same fuse clips, and the 40 A rating serves a far larger circuit than a 1.125 A branch.
6) Is 1.125A a real ampere rating, or is that a typo for 1-1/8A?
Both describe the same fuse. The Mersen catalog designation TR1-1/8R uses the fractional form, 1-1/8 amp, and the spec sheet states it as 1.125 A. If your panel schedule calls for a 1-1/8A RK5 time-delay fuse, this is it.
7) Is the Mersen TR1-1/8R rated for a circuit with high available fault current?
Yes. The interrupting rating is 200 kA AC maximum breaking capacity, which covers service and panel locations with high available fault current. It is a 250V device, so it applies on circuits at or below 250V.
8) Is the Mersen TR1-1/8R sold individually or in bulk for an MRO crib?
It is supplied 100 per pack, which suits stocking programs and maintenance cribs rather than a single replacement. Each fuse weighs 0.037 lb and measures 2 inches long.
9) Will a glass tube fuse work instead of this Mersen RK5 fuse in a motor panel?
No. Glass tube fuses like the Littelfuse AGA and AGU Series are small automotive and electronics-style fuses, not Class RK5 branch-circuit fuses, and they will not satisfy a panel that specifies RK5 time-delay protection with a 200 kA interrupting rating. Stay with the RK5 ferrule for motor branch and distribution work.
10) Is a Littelfuse AGA or AGU glass fuse a substitute for the Mersen TR1-1/8R?
No. The Littelfuse AGA5 is a 5 A AGA series glass fuse and the AGU is an AG series glass tube fuse; both are small automotive and electronic style glass cartridges. The Mersen TR1-1/8R is a Class RK5 time-delay fuse rated 1.125 A at 250 VAC/250 VDC with a 200 kA AC interrupting rating and a PolyTube body, intended for motor branch circuits and industrial control panels. The glass types carry neither the RK5 classification nor that interrupting capacity, so they should not be dropped into an RK5 holder on a power circuit.
11) I need a time-delay fuse for a 40A motor feeder, not 1.125A - what should I look at instead of the Mersen TR1-1/8R?
The Mersen TR1-1/8R is rated 1.125 A, far below a 40 A feeder. The Littelfuse CCMR040 is a CCMR series Class CC time-delay fuse rated 40 A and covers that range, provided the equipment is fitted for Class CC fuse holders. Class CC and the RK5 ferrule body the TR1-1/8R uses mount differently, so confirm which holder or fuse block the panel is built around before ordering.
12) Is this Mersen fuse RoHS compliant for a spec that requires it?
Yes, the TR1-1/8R is RoHS compliant. Construction is a PolyTube insulating body with copper connection terminals.
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