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Mersen R622 Class R Fuse Reducer, 600V AC/DC
The Mersen Class R Fuse Reducer (R Series) allows lower-rated Class R fuses to be installed into existing equipment fitted with Class R clips of a higher ampere rating, letting installers size protection closer to actual motor nameplate current for improved circuit protection. This R Series family is available in multiple reducer models — including R262, R266, and R622 — each sized to step a higher-ampere Class R clip down to a lower-ampere rejection opening, with the R622 model featured on this page. As a rejection-type reducer, it accepts only Class R fuses into Class R clips, and every model in the family is rated 600 VAC / 600 VDC with a 200 kA SCCR for demanding industrial and commercial applications. The product line is UL Listed and CSA Certified across the 30-600A range covered by the Class R standard.
Key Features
- Rejection-Type Design: Accepts only Class R fuses into Class R clips, preventing substitution of incorrectly rated fuses.
- Upgraded Circuit Protection: Allows closer-rated, time-delay Class R fuses to be used in place of renewable or one-time fuses, improving protection for motor and feeder circuits.
- Dual Voltage Rating: Rated 600 VAC and 600 VDC for broad application across AC and DC electrical systems.
- High SCCR: Short-circuit current rating of 200 kA supports use in high-fault-current environments.
- Standards Coverage: Certified to the 250V and 600V Class R standard across the 30-600A range.
- Retrofit Compatible: Fits into existing equipment with Class R clips of higher ampere rating without replacing the clip assembly.
- Model Family: Offered as R262, R266, and R622 to match the specific step-down needed for a given Class R clip.
Certifications & Compliance
- UL Listed, Guide No. IZZR, File E105670
- CSA Certified, 6225-01 207417
- Certified to 250V and 600V Class R Standards, 30-600A
Technical Specifications
- Class: R
- AC Voltage: 600 VAC
- DC Voltage: 600 VDC
- SCCR: 200 kA
- UL Certification: E105670 IZZR.E105670
- CSA Certification: 6225-01 207417
- Standards: 250V and 600V Class R - UL Listed Guide No. IZZR, CSA Certified, 30-600A
- Model: R622 (family also includes R262 and R266)
Typical Applications
- Motor Circuit Fuse Protection Upgrades
- Retrofitting Existing Class R Fuse Clips with Closer-Rated Fuses
- Industrial and Commercial Electrical Panels
- Feeder Circuit Protection Sized to Load Current
- Replacement of Renewable or One-Time Fuses with Time-Delay Fuses
Why Mersen?
Mersen Class R Fuse Reducers give electrical professionals a UL Listed, CSA Certified way to bring existing Class R fuse clips into tighter alignment with actual load requirements, without replacing equipment. With a 600 VAC/VDC rating and 200 kA SCCR shared across the R262, R266, and R622 models, these reducers support code-compliant, reliable circuit protection for motor and feeder applications where precise fuse sizing matters.
Manufacturer Resources
Mersen Product Catalog
Product Specs
- Ac Voltage:
- 600 VAC
- Ul Certification:
- E105670 IZZR.E105670
- Dc Voltage:
- 600 VDC
- Lead Free:
- Consult Technical Services
- ROHS Compliant:
- Consult Technical Services
- Csa Certification:
- 6225-01 207417
- Class:
- R
- Ce Conformity:
- Consult Technical Services
- Sccr:
- 200 kA
- list_batch:
- MERSEN-20260825
- Department:
- Electrical
- Product Group:
- Circuit Protection
- Product Type:
- Fuse Reducer
- Voltage Rating:
- 600V AC/DC
- Series:
- R Series
- Listing:
- UL Listed
- Standards:
- CSA Certified
- Product Subgroup:
- Fuse Holders & Blocks
Mersen R262 – Frequently Asked Questions
1) What does a Mersen R Series Class R fuse reducer actually do in a disconnect?
It lets you install a lower-ampere Class R fuse into equipment whose fuse clips are built for a higher ampere rating. Instead of swapping the clip assembly or the whole switch, the reducer drops into the existing Class R clips and presents a smaller rejection opening, so you can size the fuse closer to actual motor nameplate current. Common on motor and feeder circuits where the installed clips are oversized for the load.
2) Will a Mersen R622 reducer work in a panel with Class H or Class K fuse clips?
No. The R Series is a rejection-type reducer: it accepts only Class R fuses and is made to sit in Class R clips. If your switch has plain non-rejection Class H clips, a Class R reducer is the wrong part for that opening. The rejection feature is the point, it blocks substitution of an incorrectly rated fuse.
3) Which Mersen R Series reducer model do I order, R262, R266 or R622?
The three models are R262, R266 and R622, and the choice is set by the step-down you need: each one is sized to take a specific higher-ampere Class R clip down to a specific lower-ampere rejection opening. Match the model to the ampere rating of the clips already in the switch and the ampere rating of the fuse you intend to install. Voltage and interrupting specs are identical across all three, so the only ordering decision is the step-down.
4) Are Mersen R Series fuse reducers UL Listed and CSA certified for an inspected installation?
Yes. The R Series is UL Listed under Guide No. IZZR, File E105670, and CSA Certified under 6225-01 207417, certified to the 250V and 600V Class R standards across the 30-600A range. That is the paperwork an institutional or municipal inspector will ask for.
5) I have old renewable fuses in a motor disconnect. Is a reducer the right way to modernize it?
That is the main use case. A reducer lets you put closer-rated, time-delay Class R fuses into clips that are currently carrying renewable or one-time fuses, so the motor circuit gets protection sized to its real running current rather than to the oversized clip. The existing switch and clip assembly stay in place.
6) Do Mersen Class R fuse reducers hold up in a high fault current service?
The R Series is rated 200 kA SCCR, which covers high-fault-current industrial and commercial distribution. For a specifier checking the available fault current at the switch, that 200 kA figure is the number to compare against.
7) What else is available if I need a fuse clip adapter and the Mersen R Series models do not match my step-down?
Littelfuse builds the LRUR Series (also referenced as LRU2 Series) fuse reducer and clip adapter, which is the cross-brand alternative for the same job. Pick whichever family publishes the specific clip-to-fuse step-down your switch needs.
8) Does using a Mersen reducer mean I have to replace the fuse block or switch?
No. The reducer is installed into the Class R clips already in the equipment, so the clip assembly, block and switch all stay. That is what makes it a retrofit part rather than a panel rebuild, and it is why it shows up on industrial and commercial panel upgrades where downtime matters more than hardware cost.
9) What is the difference between a Mersen R Series reducer and a Littelfuse LRUR fuse clip adapter?
Both step a larger fuse clip down to accept a smaller fuse. The Mersen R Series reducer, offered as R262, R266 and R622, is specifically a rejection-type Class R device: it accepts only Class R fuses into Class R clips, and carries a 600 VAC / 600 VDC rating with a 200 kA SCCR. The Littelfuse part is identified as the LRUR Series, also called the LRU2 Series, fuse clip adapter. Match the reducer to the clip ampere rating you have and the fuse ampere rating you intend to install.
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Does the Mersen R262 come with a warranty?
Absolutely. The Mersen R262 is backed by a manufacturer’s warranty.
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