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Mersen R166 Class R Fuse Reducer, 100-60A, 600V
The Mersen R166 Class R Fuse Reducer delivers reliable amperage reduction and circuit protection for professional power distribution systems. Rated 100-60A and 600 VAC/VDC, this UL Listed and CSA Certified reducer carries a 200 kA SCCR rating, making it suitable for demanding industrial and commercial electrical environments where precise current step-down and dependable fault protection are essential.
Key Features
- 100-60A Amperage Rating: Provides precise current reduction for optimized circuit protection and load management in professional electrical systems.
- 600 VAC/VDC Voltage Compatibility: Supports both AC and DC applications up to 600V for versatile installation across diverse electrical configurations.
- Class R Design: Delivers rejection-type fuse compatibility with enhanced safety features and reliable overcurrent protection performance.
- 200 kA SCCR Rating: Provides a robust short-circuit current rating for superior fault protection in high-capacity electrical distribution systems.
- UL Listed & CSA Certified: Meets rigorous safety standards with E105670 IZZR and 6225-01 207417 certifications for professional installation confidence.
- Multi-Standard Compliance: Supports 250V and 600V Class H, K, and R applications plus 600V Class J compatibility for comprehensive system integration.
Certifications & Compliance
- UL Listed – Guide No. IZZR, E105670 IZZR.E105670
- CSA Certified – 6225-01 207417
- 200 kA Short-Circuit Current Rating (SCCR)
Technical Specifications
- Class: R
- AC Voltage: 600 VAC
- DC Voltage: 600 VDC
- SCCR: 200 kA
- Standards: 250V and 600V Class H, K, and R – UL Listed Guide No. IZZR, CSA Certified. 600V Class J – UL Listed
Typical Applications
- Industrial Power Distribution Systems
- Commercial Electrical Panels
- Manufacturing Facility Protection
- Professional Service Centers
- Electrical Contractor Installations
- Multi-Unit Power Management
Why Mersen?
The Mersen R166 Class R Fuse Reducer combines proven electrical protection technology with comprehensive safety certifications, including UL Listed and CSA Certified standards. Its 200 kA SCCR rating and multi-standard compliance across Class H, K, R, and J applications ensure reliable, code-compliant performance for electrical professionals who need dependable amperage reduction they can trust.
Manufacturer Resources
Product Specs
- Ac Voltage:
- 600 VAC
- Lead Free:
- Consult Technical Services
- Class:
- R
- Csa Certification:
- 6225-01 207417
- Rohs Compliant:
- Consult Technical Services
- Product Type:
- Fuse Reducer
- Ce Conformity:
- Consult Technical Services
- Product Group:
- Circuit Protection
- Sccr:
- 200 kA
- Department:
- Electrical
- Ul Certification:
- E105670 IZZR.E105670
- Dc Voltage:
- 600 VDC
- Product Subgroup:
- Fuse Holders & Blocks
Mersen R636 – Frequently Asked Questions
1) What does a Mersen Class R fuse reducer actually do in a disconnect switch?
It adapts oversized fuse clips down to a smaller fuse. The Mersen Class R reducers let you install a lower-amp Class R fuse in a switch built for a larger one, so you can right-size overcurrent protection to the actual load instead of replacing the disconnect. Two step-downs are offered: R166 takes 100A clips down to a 60A fuse, and R636 takes 60A clips down to a 30A fuse. Both are rated 600 VAC and 600 VDC.
2) Which Mersen reducer do I order for a 100 amp disconnect if I want to run 60 amp fuses?
Order the R166. It is the 100A clip to 60A fuse step-down. If you are going the other direction on a smaller switch, 60A clips down to a 30A fuse, that is the R636. Size by the clip in the switch first, then the fuse you intend to install.
3) Will a Class R fuse reducer hold up on a panel with a high available fault current?
The Mersen Class R reducers carry a 200 kA short-circuit current rating, which covers most industrial service and panel locations. They are UL Listed under E105670 IZZR and CSA Certified under 6225-01 207417.
4) Is the Littelfuse LRUR fuse reducer an alternative to the Mersen R166 Class R reducer?
Both are fuse clip adapters that let a smaller fuse sit in a larger fuse clip. The Littelfuse offering is the LRUR Series, also referenced as the LRU2 Series, and is described as a fuse clip adapter. The Mersen R166 is a Class R reducer rated 600 VAC and 600 VDC with a 200 kA SCCR, UL Listed under E105670 IZZR.E105670 and CSA Certified under 6225-01 207417. When cross-shopping, match the reducer to the clip size in your disconnect and the fuse amperage you intend to install, since the Mersen units are sold as specific step-downs: 100A clip to 60A fuse and 60A clip to 30A fuse.
5) My disconnect has 60A clips and I want to run 30A fuses - is the R166 the right part?
No. The R166 step-down is 100A clip to 60A fuse. For 60A clips taking a 30A fuse, the Mersen part is the R636. Both are Class R reducers rated 600 VAC and 600 VDC with a 200 kA SCCR. If your clip and fuse sizes fall outside those two steps, a Littelfuse LRUR Series fuse clip adapter is the other reducer line to look at.
6) Can I use these Mersen reducers on a DC circuit, not just AC?
Yes. Both the R166 and R636 are rated 600 VDC as well as 600 VAC, so they work in DC distribution and drive applications up to 600V.
7) Do these reducers only work with Class R fuses, or can I use Class H, K or J too?
The reducers themselves are Class R. Per the published standards coverage, they are UL Listed and CSA Certified for 250V and 600V Class H, K and R, and UL Listed for 600V Class J. Note the Class R rejection feature is what keeps a non-current-limiting fuse out of a rejection-style switch, so confirm the fuse you install matches the protection the panel schedule calls for.
8) Is a fuse reducer an acceptable way to downsize protection instead of swapping the disconnect?
That is exactly what it is for. Rather than replacing a 100A disconnect because the load only needs 60A of protection, the R166 adapts the existing clips to accept the 60A fuse. It keeps the UL Listed, CSA Certified assembly intact at 600V with a 200 kA short-circuit rating, which is why they show up in industrial power distribution and commercial panel work.
9) I need a reducer for a DC circuit - does the Littelfuse LRUR or the Mersen R166 cover it?
The Mersen R166 Class R reducer is rated for both AC and DC service at 600 VAC and 600 VDC, so it suits DC power distribution as well as AC panels. The Littelfuse comparable is the LRUR Series fuse clip adapter, offered as a series rather than with a stated DC rating, so for a DC application the Mersen R166 is the one to specify on ratings you can point to on a submittal.
10) How many reducers do I need for a three phase disconnect?
One reducer set per fuse. A reducer adapts a single fuse position, so a three-pole 100A switch being stepped to 60A fuses takes three R166 units, one per phase. Order quantity by pole count, not by switch.
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Does the Mersen R636 come with a warranty?
Absolutely. The Mersen R636 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
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