VICFUSE UL Standard Class Series Fuse Holders: Quality, Reliability, and Industrial Protection

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A design engineer specifying a compact industrial panel reaches for a Class CC fuse holder. It's UL Listed under File No. E359089, rated 600V AC/DC, and built with a rejection feature that physically stops a lower-rated fuse from ever being substituted in the field. That combination — a documented UL file number plus a mechanical safeguard — is exactly why Class CC clears agency review cleanly and doesn't come back for rework. Not every UL fuse class in this family offers that same certification, and knowing what applies to a given class before the bill of materials is finalized changes how a panel gets specified.

VICFUSE is also expanding this lineup with Class CF, a current-limiting fuse built to Class J electrical performance in roughly 70% less body size, with finger-safe, touch-proof construction for designs where that combination of compactness and personnel protection matters most.

Class CC Fuse Holders

Class CC is the smallest class here and the usual starting point when panel space is tight. VICFUSE's blocks are rated 600V AC/600V DC with 1,200V minimum dielectric strength, tin-plated copper terminals on a zinc-plated steel thermoplastic base, and UL94 V-0 flammability. Blocks come in 30A and 60A variants, both DIN-rail mountable, with a non-DIN interlocking option for ganging any number of poles. Blown-fuse indication is available on the 60A line, and the rejection feature stops a lower interrupting- or voltage-rated fuse from being inserted during a field replacement.

The dedicated VRB10-CC holder is touch-safe, snap-together, rated 600V AC/DC at 30A per pole in 1- to 3-pole configurations, with a 3,000V AC dielectric withstand and a 200kA RMS symmetrical withstand rating. It's rated -40°C to +85°C indoor service and carries UL File No. E359089. Its LED-indicating version illuminates only while energized, confirming the circuit is live — it doesn't replace the blown-fuse indicator on the fuse body, which keeps showing an open fuse after de-energization and lockout.

Class CC and Midget blocks are the only platforms with 1/4" Quick Connect terminals (20A); elsewhere it's screw, screw-with-pressure-plate, or box lug.

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Applications: These holders accommodate Class CC fuse types, each suited to a different job, VCT time-delay fuses for small motors, contactors, lighting, heating, and general loads; VCF fast-acting fuses for control circuits and branch circuit protection with no delay needed; and VCTMP for motor and motor branch circuit protection specifically.

Cross Reference: Class CC geometry is standardized under UL 248-4. Comparable series: Littelfuse's L600C, Mersen's 30300-prefix, Eaton Bussmann's BCM603, and Marathon's 6CC-prefix parts, comparable designations, not confirmed drop-ins. Verify voltage, current, interrupting rating, dimensions, and certification before substituting.

Class J Fuse Holders

Class J covers the broadest range here — 600V at 1–600A off one platform — with a footprint up to 45% smaller than earlier designs. Leakage current stays below 0.6mA at 600V, flammability is UL94 V-0, and reinforced fuse clips are standard. Indication is available on every amperage except 200–600A, and covers are offered for 100A and below only.

Termination changes with amperage: 30A takes box lug (6–14 AWG), pressure plate (10–14 AWG), or screw (10–22 AWG), copper only. 60A opens to 2–14 AWG copper-aluminum; 100A moves to 2/0–14 AWG solid or stranded copper-aluminum. From 200A up, it's box lug only, no DIN mounting — 250 kcmil to 6 AWG at 200A, two parallel runs of 350 kcmil to 1/0 AWG at 400A, and two parallel runs of 500 kcmil to 4 AWG at 600A.

VICFUSE’s VFPSJ POWR-SAFE dead-front holder is rated 600V AC/DC with a 200kA interrupting rating, 30A and 60A, 1- to 3-pole, IP20, pressure-plate terminated, 35mm DIN-rail mountable with tool-free fuse removal, LED indication across 110–600V, and UL File No. E359089. Littelfuse's LFPSJ is a directly comparable product, confirming this dead-front design is an established category.

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Applications: VJT time-delay fuses cover motor circuits, mains, feeders, branch circuits, lighting, heating, transformers, control panels, circuit-breaker backup, and load centers. VJF fast-acting fuses suit solid-state motor controller starting circuits and power semiconductor protection — diodes, SCRs, GTOs, SSRs. VJD high-speed fuses serve the same semiconductor role for AC/DC drives and controllers with an even lower let-through I²t.

Cross Reference: Class J is standardized under UL 248-8. Comparable series: Littelfuse's LFJ blocks and LFPSJ holders, Mersen's 60300-series, Eaton Bussmann's J60030 line, and Marathon's R6J-prefix parts. Confirm voltage, interrupting rating, and wire range before assuming interchangeability.

Class T Fuse Blocks

Class T's advantage is compactness relative to interrupting capacity — the fuse body runs noticeably smaller than Class R at the same amperage. VICFUSE offers 300V AC and 600V AC lines, both 1–600A with a 200kA RMS symmetrical withstand rating and leakage below 0.6mA at 600V. Reinforced clips and universal mounting holes are standard, and one-hand DIN release is built into the 30–60A range. At 100A, wire range runs 2/0–6 AWG (with 8 AWG and 10–14 AWG options); at 200A and up, it's box lug only, scaling from 250 kcmil at 200A/400A to 500 kcmil at 600A, with no DIN mounting.

Cover availability splits the two voltage lines: 300V offers covers through 100A only, while 600V offers covers through 600A — the line to specify if enclosed terminals are needed above 100A.

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Applications: This block accommodates VTF fast-acting fuses, documented for load centers, panelboards, switchboards, and feeder circuits — applications where Class T's compact body and 200kA withstand both matter without Class R's larger footprint.

Cross Reference: Comparable series: Littelfuse's LFT-prefix blocks, Mersen's 30300/60300-series, Eaton Bussmann's T-prefix line, and Marathon's RT- and R6T-prefix parts. Confirm voltage class, interrupting rating, and wire range before finalizing a substitute.

Class G Fuse Blocks

Class G's voltage rating changes with amperage: 600V AC for 1–20A, 480V AC for 25–60A. This isn't arbitrary — Class G fuses use length-coded bodies so a fuse with the wrong voltage or amperage rating can't be forced into the wrong holder. The documented block rating is AC; a DC application needs confirmation against the specific fuse and block combination rather than assumption.

UL94 V-0 applies across the line, mounting is snap-to-release DIN rail, and one-hand release covers most amperages. Base temperature runs 150°C on the 15A, 20A, and 30A blocks, versus 125–130°C typical elsewhere, while the 60A/480V variant steps down to 125°C with copper-aluminum termination (2-4 AWG to 6-14 AWG). Smaller amperages use copper-only termination across screw, pressure plate, and box lug.

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Applications: This block accommodates VGT time-delay fuses, documented specifically for branch-circuit protection on lighting and heating loads. Class G has been losing ground to Class CC in new designs, since Class CC offers a comparable or smaller footprint with higher voltage and interrupting ratings.

Cross Reference: Comparable series: Littelfuse's LFG-prefix blocks, Mersen's 40000-series, Eaton Bussmann's BG30-prefix line, and Marathon's G-prefix parts. The voltage-amperage split is a hard constraint — verify it against system voltage first.

Class H/K5, Class R, and RK1/RK5 Fuse Blocks

Class H/K5 and Class R blocks carry RoHS marking only; RK1 elements (VKF/VKT) additionally carry CE marking; RK5 (VRK5) carries RoHS marking only. None carry the UL file number documented for CC, J, T, and G — confirm certification directly before a UL panel submission.

Class H/K5 blocks are rated 250V and 600V, 1–600A, with a 10kA RMS symmetrical withstand rating and no rejection feature, so the block will physically accept either a Class H or Class R fuse. Installing a higher-rated Class R fuse in a Class H block gains the fuse's interrupting capability, but the block's 10kA withstanding doesn't change — the block stays the limiting factor. Class H/K5 tends to be reserved for retrofits or lower-fault-current installations where 10kA has been confirmed adequate.

Class R shares the same range and footprint as Class H but steps up to 200kA — twenty times the withstand rating in the same enclosure space, and adds a rejection feature blocking anything but a Class R fuse. That combination makes it the default for new builds, especially where fault current might rise as upstream equipment changes.

RK1 and RK5 aren't separate blocks — they're UL sub-classifications of Class R fusing mounted in the same rejection-style Class R block. RK1 (VKF/VKT) covers fast-acting and time-delay variants; RK5 (VRK5) is time-delay only. Reinforced fuse clips are standard on both Class H/K5 and Class R blocks. Termination is richest at 30A (screw, pressure plate, box lug all available); at 60A and up, it's box lug only, from 2-4 AWG at 60A to 500 kcmil at 600A.

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Applications: VKF (fast-acting RK1) covers load centers, panelboards, switchboards, feeder circuits, lighting, and non-inductive loads. VKT (time-delay RK1) covers large motors, motor controllers, transformers, disconnects, control panels, and safety switches. There's no separately documented application list for VRK5 or for Class H/K5 as a standalone product — VRK5 is simply the recommended fuse for both, so the real selection decision comes down to withstand rating and rejection feature.

Cross Reference: Comparable series: Littelfuse's LFH- and LFR-prefix lines, Mersen's 20000-series, Eaton Bussmann's H/R-prefix blocks, and Marathon's RF/R-prefix parts. Given how close H/K5 and R sit dimensionally, confirm withstand rating and rejection-feature presence before substituting.

How to Select the Right Fuse Holder

1. Match system voltage. Class G's documented block rating is AC only, so DC applications need confirmation against the fuse itself.

2. Size for available fault current. If unknown or variable, specify a 200,000A interrupting-rated fuse with a matching 200,000A withstand block, ruling out Class H for most new designs.

3. Match fuse type to load. Performance class matters as much as amperage — time-delay for motor inrush, fast-acting for resistive loads, high-speed for semiconductors.

4. Confirm code requirements with the approving agency.

5. Pick termination type. Screw for spade/ring terminals; pressure plate for vibration; box lug for solid or Class B/C stranded wire; 1/4" Quick Connect (20A) only on Midget and Class CC.

6. Set pole count per the ordering table.

7. Check DIN-rail availability, which generally disappears at 200A and above.

8. Consider reinforced clips — standard on Class J, T, H/K5, and R blocks.

Getting the Class Right Before Panel Review

A Class CC block's rejection feature keeps a lower-rated fuse out during a rushed field repair — and its UL File No. E359089 means that safeguard is backed by documented certification, not just design intent. A Class H block and a Class R block sit in the same panel footprint; only one survives a 200kA fault event. A Class J block with indication flags an open fuse before a technician spends an hour chasing a dead circuit. None of this is abstract — it's the difference between a panel that clears agency review the first time and a fuse replacement that quietly reintroduces risk. For part-level guidance and full datasheets, contact VICFUSE's applications team directly.

What's Next: VICFUSE's Class CF Fuses?

Every class covered above solves for a specific voltage, current, or footprint constraint. Class CF is VICFUSE's answer to a different one: panels where even Class J's footprint is too large, and where finger-safe, touch-proof construction matters as much as interrupting capacity. It's a current-limiting fuse built to Class J electrical characteristics in a body roughly 70% smaller, with finger-safe construction that keeps live parts inaccessible during handling — a meaningful difference for personnel safety during routine fuse replacement.

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VICFUSE's Class CF line splits into four series by application. VUCF (fast-acting, 600V AC/DC, 1–600A, interrupting rating up to 300kA AC at lower amperages) targets UPS and critical power infrastructure. VUCT (time-delay, 600V AC/DC, 1–600A, minimum 10-second operating time at 500% rated current) covers general-purpose protection. VUCFP (fast-acting, 600–2000V DC, 35–600A, 50kA DC interrupting rating) is built specifically for the low-fault-current conditions typical of photovoltaic systems. VUCFW (fast-acting, 690–1140V AC, 1–250A) serves the same low-fault-current role in wind power generation. All four series are available with an indicator option, and each pair with a corresponding VCFH-series fuse holder sized to the amperage range, including a dedicated VCFH-W holder line for the wind power series.

Engineers evaluating Class CF for a specific project should confirm current certification and availability status directly with VICFUSE before specifying.

FAQ

What's the difference between a fuse block and a fuse holder? A fuse block is a fixed, panel-mounted termination assembly; a fuse holder is a modular unit built for easier access and removal, like VICFUSE's VRB10-CC and VFPSJ.

Q-1: What are the VRB10-CC's ratings? 600V AC/DC at 30A per pole, 1- to 3-pole, 200kA RMS symmetrical withstand, 3,000V AC dielectric withstand.

Q-2: What's the difference between Class H and Class R fuse blocks? Class R carries 200kA withstand and a rejection feature; Class H carries only 10kA with no rejection feature, in the same 250V/600V, 1–600A range and footprint.

Q-3: Can a Class H fuse fit in a Class R block? No — the rejection feature in the Class R block physically prevents anything but a Class R fuse.

Q-4: What termination options does VICFUSE offer? Screw, screw with pressure plate, box lug, and 1/4" Quick Connect (20A, Midget and Class CC only). Box lug becomes standard, often the only option, at higher amperages.

Q-5: Are VICFUSE fuse holders UL listed? Class CC, Class G, Class T, Class J, the VRB10-CC, and the VFPSJ carry UL File No. E359089. Class H/K5, R, RK1, and RK5 carry CE and/or RoHS marking only.

Q-6: What's the leakage current on an indicating holder? Class J, H/K5, R, and T indicating blocks are below 0.6mA at 600V; the general spec is below 1mA typical.

Q-7: At what voltage does the blown-fuse indicator operate? Neon indicators run 80–600V AC; the VFPSJ's LED covers 110–600V and confirms the circuit is live, unlike a blown-fuse indicator, which shows an open fuse even after de-energization.

Q-8: What's unique about Class G's voltage rating? It's split by amperage — 600V AC for 1–20A, 480V AC for 25–60A — from length-coded body dimensions, not an adjustable spec.

Q-9: What's the withstand rating of Class R and Class T? Both carry 200kA RMS symmetrical — twenty times Class H's rating for Class R, in the same footprint.

Q-10: What are Class CC fuse holders typically used for? Small motors, contactors, lighting, and heating with VCT fuses; control circuits with VCF fuses; motor branch circuit protection with VCTMP fuses.

Q-11: What is VICFUSE's Class CF fuse line? Class CF is a current-limiting fuse built to Class J electrical performance in roughly 70% less body size, with finger-safe, touch-proof construction. It splits into four series — VUCF (fast-acting), VUCT (time-delay),

VUCFP (photovoltaic fast-acting), and VUCFW (wind power fast-acting), each paired with a corresponding VCFH-series fuse holder.

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