VICFUSE VCF Class CC Fast-Acting Fuse: Complete Technical Guide

The VICFUSE VCF is a fast-acting, current-limiting Class CC fuse rated for 600V AC and 600V DC service. It is built to UL 248-4, Low-Voltage Fuses — Part 4: Class CC Fuses, and listed under UL File Number E479968. The VCF covers control circuits, lighting, general loads, branch circuit protection, and non-inductive loads not requiring time-delay, across a current range of 0.1A to 30A. This guide covers UL 248-4 specifications, electrical ratings, I²t data, NEC-based selection calculations, suitable and unsuitable applications, and a FAQ section addressing the questions engineers ask most often.

What Defines the VCF as a Class CC Fuse?

Governing Standard: UL 248-4

Class CC fuses are governed by UL 248-4, Low-Voltage Fuses — Part 4: Class CC Fuses. UL 248-4 defines the physical form factor, electrical performance requirements, current-limiting behavior, and the rejection feature that distinguishes Class CC from lower-performance fuse classes. The VCF body measures Φ10.32mm diameter by 38.1mm in length — the 13/32 inch x 1-1/2 inch Class CC form factor.

Rejection Feature

Class CC fuses have a specific ferrule geometry — defined by UL 248-4 — called the rejection feature. This feature ensures that only current-limiting Class CC fuses can be installed in Class CC holders. It prevents substitution with non-current-limiting fuses of similar physical dimensions that do not meet Class CC performance requirements.

Current-Limiting Characteristic

The VCF opens fast enough during a fault to limit peak let-through current below the available prospective fault current. This protects downstream equipment from the full destructive energy of an unrestricted short circuit. Engineers can verify specific let-through current values using the Peak Let-Through Curve published in the VCF datasheet.

Fast-Acting Characteristic

The VCF has no intentional time delay. It responds immediately to overcurrent, which makes it well-suited for non-inductive loads and poorly suited for loads with starting inrush. If the load is a motor, transformer, or contactor, the VCF is the wrong series — fast-acting operation will trip on inrush before the load reaches steady state. Use the VICFUSE VCT or VCTMP series for those applications.

VCF Ratings and Specifications

The interrupt rating difference between AC and DC service, 200kA at 600V AC versus 50kA at 600V DC, reflects a fundamental difference in arc extinction behavior. AC current passes through zero 120 times per second at 60Hz, which assists the fuse in extinguishing the arc naturally. DC circuits have no natural current zero-crossing, so the fuse must actively suppress the arc entirely through its own interruption mechanism. Engineers protecting DC circuits must verify that 50kA at 600V DC exceeds the available fault current at the point of installation, per NEC Article 110.9.

The VCF is available in 27 current ratings spanning 0.1A to 30A:

Electrical Characteristics — I²t Data

Pre-arc I²t is the thermal energy let through from fault initiation until the fuse element begins to melt; at this stage, the fuse has not yet started interrupting. 

Clearing I²t is the total thermal energy from fault initiation through complete arc extinction. Clearing I²t is the value used for equipment protection analysis.

The ratio of clearing I²t to pre-arc I²t is approximately 3.5:1 across the VCF range. This ratio is characteristic of fast-acting current-limiting fuse behavior and confirms the VCF's ability to limit let-through energy during fault conditions.

Application: PCB rectifier diode with a rated I²t withstand of 1,000 A²S. The table below shows how fuse selection determines whether the component is protected.

Maximum suitable rating for this diode: VCF-15A-600VAC/DC.

Applications

Where the VCF Is Used

Control Circuits

The VCF protects PLC outputs, relay coils, 24VDC and 120VAC control wiring, and panel indicators. Ratings from 0.1A to 2A cover the majority of control circuit protection needs, and the fast-acting characteristic provides immediate response without delay. Selection example: 120VAC panel with 6 relay coils drawing 120mA each, total 720mA × 1.25 (NEC Article 240 / 409.21) = 900mA minimum; select VCF-1A-600VAC/DC.

Lighting Branch Circuits

The VCF is suitable for resistive and non-inductive fluorescent lighting on 120V or 277V branch circuits. Fast-acting operation is acceptable for these loads because non-inductive lighting does not produce starting inrush. Selection example: 277VAC fluorescent branch circuit with a continuous load of 7.2A — 7.2A × 1.25 = 9A minimum; select VCF-10A-600VAC/DC.

General Branch Circuits

The VCF serves non-inductive loads using 15A to 30A ratings for industrial branch circuit applications. Selection example: 480V general branch circuit with a continuous load of 16A — 16A × 1.25 = 20A minimum; select VCF-20A-600VAC/DC.

Instrumentation and Signal Circuits

Ratings from 0.1A to 0.5A serve signal circuits and low-power electronics where fine current resolution is required. Standard fuse ranges rarely provide this granularity, making the VCF a practical choice for precision instrumentation protection where a 1A or 2A fuse would offer insufficient discrimination.

Where the VCF Is Not Suitable

Motor starting inrush is typically 6 to 10 times full-load amperes, sustained for several seconds. Transformer energization inrush is typically 8 to 12 times rated current during the first cycles. The VCF fast-acting characteristic will operate on this inrush, causing nuisance tripping before the load reaches steady-state operation. For motor branch circuit protection, use the VICFUSE VCTMP series. For transformers and contactors, use the VICFUSE VCT series.

Compatible Fuse Holders for the VICFUSE VCF

The VCF requires a Class CC rated holder sized for the 10×38mm form factor at 600V and 30A. The fuse dimensions and rating are fixed;  holder selection comes down to mounting method, pole count, and terminal style. 

DIN-Rail Fuse Blocks

For DIN-rail panel installations, select the fuse block by pole count (1, 2, or 3) and terminal type. Three terminal styles are available: box lug, pressure plate, and screw. The table below lists VICFUSE part numbers with Littelfuse, Mersen, and Bussmann cross-references for the full 600V, 30A Class CC range.

The compatible cover number for all Class CC 30A DIN-rail blocks in the table above is VSPL001. Cross-references allow direct replacement when the installed panel standard uses a Littelfuse, Mersen, or Bussmann block.

Single-Pole Holders and PCB Clips

For single-pole panel mounting, inline mounting, or PCB-level retention, the following VICFUSE options are available. All single-pole holders listed are rated 600V, 30A, 1-pole, for the 10×38mm Class CC fuse. The VF-700 PCB clip is rated 1500V, 60A and accepts the same 10×38mm fuse size for board-level mounting.

Select V-75HW for applications where the holder is exposed to moisture or requires a weatherproof enclosure. The VF-700 is the correct choice when the VCF mounts directly to a PCB rather than a panel holder.

Vicfuse: Single-Pole Holders and PCB Clip for Class CC

Selection Guidance

Three criteria determine the correct holder: mounting method (DIN-rail block, single-pole panel or inline, or PCB), required pole count (1, 2, or 3 for DIN-rail blocks), and terminal type (box lug, pressure plate, or screw). Confirm the selected holder is rated Class CC for the 10×38mm form factor at 600V before finalizing. Verify conductor size and wiring method are compatible with the terminal style in use.

Frequently Asked Questions

What is the interrupt rating of the VICFUSE VCF fuse?
The VICFUSE VCF carries an interrupt rating of 200kA at 600V AC and 50kA at 600V DC. The DC rating is lower because DC circuits have no natural current zero-crossing to assist arc extinction. AC current passes through zero 120 times per second at 60Hz, which aids interruption. DC arcs must be suppressed entirely by the fuse mechanism, which reduces the achievable interrupt capacity.

Is the VCF a current-limiting fuse?
Yes. A current-limiting fuse opens fast enough during high fault current conditions to prevent the fault current from reaching its prospective peak value. The VCF meets the current-limiting requirements of UL 248-4. Engineers can verify specific let-through current values for a given fault level using the Peak Let-Through Curve in the VCF datasheet.

Can I use the VCF on a motor branch circuit?
No. Motor starting inrush is typically 6 to 10 times full-load amperes, sustained for several seconds. The VCF fast-acting characteristic will operate on this inrush, causing nuisance tripping before the motor reaches steady-state speed. For motor branch circuit protection, use the VICFUSE VCTMP series, which is designed specifically for motor protection per NEC Article 430.

What standard governs Class CC fuses?
Class CC fuses are governed by UL 248-4, Low-Voltage Fuses — Part 4: Class CC Fuses. This standard defines the physical form factor, rejection feature, electrical performance requirements, and current-limiting behavior for all Class CC fuses. The VICFUSE VCF is listed under UL File Number E479968.

What fuse holder is compatible with the VCF?
The VCF requires a Class CC rated fuse holder designed for the 13/32 inch x 1-1/2 inch (Φ10.3mm x 38.1mm) form factor. Class CC holders incorporate the rejection feature, a specific ferrule geometry defined by UL 248-4, that ensures only current-limiting Class CC fuses can be installed. This prevents field substitution with non-current-limiting fuses of similar physical dimensions that do not meet Class CC performance requirements.

How do I size a VCF for a continuous load?
Multiply the continuous load current by 1.25, then select the next available VCF rating above that calculated value. For branch circuit applications, this factor is required by NEC Article 210.20(A). For industrial control panel applications, overcurrent protection is governed by NEC Article 409.21, which directs compliance with NEC Article 240. Example: 720mA continuous load × 1.25 = 900mA minimum required rating. The next available VCF rating above 900mA is 1A. Selected fuse: VCF-1A-600VAC/DC.

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