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Mersen 632 Class H & K Fuse Reducer, 600VAC/600VDC Rated, 50kA SCCRThe Mersen 632 Class H & K Fuse Reducer allows Class H and K fuse clips to accept smaller fuse sizes, making it a practical solution...
Mersen
$95.60
$50.66
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Mersen 132 Class H & K Non-Rejection Fuse Reducer
The Mersen Class H & K Non-Rejection Fuse Reducer family lets electricians and maintenance teams fit lower-rated Class H, K, or R fuses into existing equipment whose clips are sized for higher ampere ratings, without replacing the clips themselves. Available across the family in two models (132 and 166) to cover different reducer configurations, every unit shares the same core ratings: 600 VAC and 600 VDC, a Short-Circuit Current Rating (SCCR) of 50 kA, and UL Listing plus CSA Certification. By enabling closer-rated time-delay fuses to replace older renewable or one-time fuses, this reducer helps size protection nearer to actual load current, such as motor nameplate amperage, improving overall circuit protection and reducing nuisance outages. Whether upgrading a single branch circuit or retrofitting a panel, the Mersen non-rejection reducer is a practical way to modernize fuse protection without tearing out existing fuse clips.
Key Features
- Non-Rejection Design: Allows Class H, K, or R fuses to fit into existing Class H or K clips, enabling flexible fuse downsizing without clip replacement.
- Voltage Rating: Rated 600 VAC and 600 VDC for use across a wide range of circuit protection applications.
- Short-Circuit Current Rating: 50 kA SCCR supports demanding fault-current environments common in industrial and commercial systems.
- Improved Circuit Protection: Enables use of closer-rated time-delay fuses in place of renewable or one-time fuses, sizing protection nearer to actual load current such as motor nameplate current.
- Recognized Standards: Meets 250V and 600V Class H, K, and R standards under UL Listed Guide No. IZZR and CSA Certification.
- Model Range: Offered as Model 132 or Model 166 to match the reducer configuration required by the installation.
Certifications & Compliance
- UL Listed, Guide No. IZZR, File E105670
- CSA Certified, 6225-01 207417
- Meets UL/CSA Standards for 250V and 600V Class H, K, and R fuse reducers
Technical Specifications
- AC Voltage: 600 VAC
- DC Voltage: 600 VDC
- UL Certification: E105670 IZZR.E105670
- CSA Certification: 6225-01 207417
- SCCR: 50 kA
- Class: H & K
- Standards: 250V and 600V Class H, K, and R - UL Listed Guide No. IZZR, CSA Certified
- Model Options: 132, 166
Typical Applications
- Motor Control and Overcurrent Protection Circuits
- Retrofitting Existing Fuse Clips with Closer-Rated Fuses
- Industrial and Commercial Electrical Equipment
- Panelboard and Switchgear Fuse Protection Upgrades
Why Mersen?
Mersen fuse reducers are UL Listed and CSA Certified, engineered to help electrical professionals upgrade circuit protection without replacing existing fuse clips. With a 50 kA SCCR and support for Class H, K, and R fuse types across both the 132 and 166 models, Mersen delivers dependable, code-compliant performance for demanding industrial and commercial electrical systems.
"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:
- H & K
- Ce Conformity:
- Consult Technical Services
- Sccr:
- 50 kA
- list_batch:
- MERSEN-20260825
- Department:
- Electrical
- Product Group:
- Circuit Protection
- Product Type:
- Fuse Reducer
- Voltage Rating:
- 600V
- Listing:
- UL Listed
- Standards:
- CSA Certified
- Product Subgroup:
- Fuse Holders & Blocks
Mersen MER132 – Frequently Asked Questions
1) Will a Mersen 132 or 166 reducer work in a 600 volt panel, or is it 250 volt only?
Both are rated 600 VAC and 600 VDC, so they cover 240V and 480V motor circuits as well as 600V systems. The DC rating also means they can be used in DC circuit protection, which not every reducer states.
2) Is this fuse reducer UL Listed and can I use it on a panel with a high available fault current?
UL Listed under Guide No. IZZR, File E105670, and CSA Certified under 6225-01 207417. The short-circuit current rating is 50 kA, so it can stay in service on gear where the available fault current is within that figure.
3) Does a non-rejection fuse reducer let me put a Class H fuse where a Class R fuse is required?
Non-rejection means the reducer does not include the rejection feature that blocks a Class H fuse from a Class R clip. It will take Class H, K, or R fuses into Class H or K clips. If your equipment is specified for rejection-type Class R fuses only, a non-rejection reducer is the wrong choice, since the whole point of an R clip is to prevent a lower interrupting rated H fuse being installed.
4) Do I have to replace the fuse block to downsize the fuses in an old motor disconnect?
No. That is exactly what the reducer avoids. It adapts the existing Class H or K clips to a smaller fuse, so the block, switch and enclosure stay in place, and you keep the UL Listed 600V/50 kA reducer in the circuit instead of doing a gear change.
5) Which fuse reducer should I use if I need a rejection-style adapter instead of a non-rejection one?
The Mersen Class H and K reducer is specifically a non-rejection design, so it will accept Class H, K, or R fuses in Class H or K clips without enforcing a Class R rejection feature. If your application requires a rejection-style adapter that restricts the holder to Class RK fuses, look to the Littelfuse LRUR series, also listed as the LRU2 series, of fuse reducers and clip adapters. Confirm the class marking on the switch or panelboard before selecting either.
6) Can fuse reducers be used to improve motor overcurrent protection on existing equipment?
Yes, and that is the most common use. Older switches were often fused with renewable or one-time fuses well above the load. Dropping in a reducer lets you fit a closer-rated time-delay fuse matched nearer to the motor nameplate current, which tightens overload and short-circuit protection on motor control and overcurrent circuits without new gear.
7) Do I need a fuse reducer at all, or can I just install a smaller fuse in the existing clips?
A smaller ampere fuse has a shorter, narrower body than the clips of a higher-rated holder, so it will not seat. The Mersen Class H and K non-rejection reducer bridges that gap and lets you drop in a closer-rated time-delay fuse, such as sizing motor protection nearer to nameplate current, without replacing the clips. It is rated 600 VAC and 600 VDC with a 50 kA SCCR, UL Listed under Guide No. IZZR and CSA Certified. The Littelfuse LRUR series covers the same clip adapter function if you are standardizing on that brand.
8) What is the difference between a Mersen non-rejection fuse reducer and the Littelfuse LRUR series fuse clip adapter?
Both are fuse clip adapters that let a smaller fuse be mounted in larger existing fuse clips. The Mersen Class H and K non-rejection reducer, offered as models 132 and 166, is rated 600 VAC and 600 VDC with a 50 kA short-circuit current rating, and its non-rejection design accepts Class H, K, or R fuses in Class H or K clips. The Littelfuse alternative is the LRUR series, also catalogued as the LRU2 series, of fuse reducers and fuse clip adapters. Match the reducer to the clip class and the fuse class you intend to install.
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Does the Mersen MER132 come with a warranty?
Absolutely. The Mersen MER132 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
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