Class CC Motor Branch Circuit Protection Fuses: Complete Technical Guide | Vicfuse VCTMP

The VICFUSE VCTMP is a time-delay, current-limiting Class CC fuse designed specifically for motor and motor branch circuit protection, rated 600V AC and 600V DC. The Class CC series covers current ratings from 0.1A to 30A, while the Class CD series covers 35A to 60A according to UL 248-18,  double the 30A maximum of the VCT; covers motor circuits where NEC 430.52 calculations exceed standard ranges. This guide explains how VCTMP differs from VCT and VCF, its full specifications, NEC 430.52 sizing with worked examples, holder selection, and where the series is not the right choice.

What Makes VCTMP Different from VCT and VCF

All three Class CC series share the same UL 248-4 standard and rejection feature. The differences are purpose, current range, and physical size.

Purpose:  VCTMP is designed specifically for motor and motor branch circuit protection. VCT is a general time-delay fuse,  it can protect some small motors but was not designed for NEC 430 motor branch circuit use. VCTMP was built specifically around NEC 430 motor protection requirements.

Extended range to 60A: VCT tops out at 30A. NEC 430.52 motor fuse calculations at 300% of FLA frequently produce required ratings above 30A. VCTMP extends to 60A to serve the motor circuits that VCT cannot.

Two body sizes:  Ratings from 0.1A to 30A use a 38.1mm body that is compatible with the standard Class CC holder. Ratings from 35A to 60A use a 47.8mm body; a different physical size that requires a holder designed for 47.8mm. 
NEC Class CC multiplier:  Under NEC Table 430.52, Class CC time-delay fuses are permitted at 300% of motor FLA as the standard maximum, while standard dual-element time-delay fuses are limited to 175%. If 300% is still insufficient for motor starting, Class CC can increase to 400% , versus 225% for dual-element. This NEC advantage gives VCTMP more starting tolerance for hard-starting motor loads than conventional time-delay fuses at the same current rating.

VCTMP Ratings and Specifications

The DC interrupt rating of 50kA at 600V DC is lower than the 200kA AC rating, consistent with VCF and VCT. DC circuits have no natural current zero-crossing to assist arc extinction, so the interrupting capacity in DC service is reduced relative to AC.

How to Size VCTMP for Motor Branch Circuit Protection?
Motor branch circuit fuses protect conductors, motor control apparatus, and motors against short circuits and ground faults per NEC Article 430. They do not provide motor overload protection;  that is the function of the overload relay per NEC 430.32. The fuse must hold motor starting inrush, typically 6 to 7 times FLA, without operating.

Per NEC Table 430.52, Class CC time-delay fuses are permitted at 300% of FLA as standard maximum and 400% if needed, while dual-element time-delay fuses are limited to 175% standard and 225% maximum. For the same motor, VCTMP can be sized larger than a standard dual-element fuse, giving more starting tolerance for hard-starting loads without sacrificing protection.

Use FLA from NEC Table 430.250 (three-phase) or NEC Table 430.248 (single-phase) for all calculations. Never use motor nameplate FLA. This is the most common error in motor branch circuit fuse sizing.

Where VCTMP Is Not Suitable

VCTMP is optimized for motor branch circuit protection. When NEC 430.52 at 300% or 400% produces a required rating exceeding 60A, Class J or Class R time-delay fuses with higher current ranges are req For transformer and contactor protection, the VCT is the more appropriate choice within its 30A range.

Frequently Asked Questions

Why does VCTMP extend to 60A when VCT only goes to 30A?
Motor branch circuit fuse ratings per NEC 430.52 use 300% of motor FLA as the standard maximum for Class CC time-delay fuses. A motor with 14A FLA requires a 45A fuse at 300%, far exceeding VCT's 30A ceiling. VCTMP extends to 60A specifically to cover these NEC 430.52 motor calculations.

What NEC multiplier applies to VCTMP for motor branch circuits?
NEC Table 430.52 permits Class CC time-delay fuses at 300% of motor FLA as standard maximum, with 400% permitted if 300% is insufficient for motor starting. These limits are higher than standard dual-element time-delay fuses (175% standard, 225% maximum). Always size from NEC table FLA, not motor nameplate FLA.

Do 35A to 60A VCTMP fuses fit standard Class CC holders?
No. The 35A to 60A VCTMP uses a 47.8mm body , longer than the 38.1mm standard Class CC form factor. A fuse holder designed for the 47.8mm body is required. This must be verified during panel design, not after the panel is built and wired.

When should I use VCTMP instead of VCT for motor protection?
Use VCTMP when an NEC 430.52 calculation at 300% of motor FLA produces a required rating above 30A,  beyond VCT's maximum. Also use VCTMP when the application specifically requires a fuse designed for motor branch circuit protection per NEC Article 430.

What is the interrupt rating of VCTMP?
200kA at 600V AC and 50kA at 600V DC, the same interrupt ratings as VCF and VCT. The DC rating is lower because DC circuits have no natural current zero-crossing to assist arc extinction. Verify that 50kA DC exceeds available fault current per NEC Article 110.9.

Can VCTMP protect a 25HP 460V motor?
Check the calculation first. A 25HP 460V motor has an FLA of 34A per NEC Table 430.250. At 300%: 34A × 3.0 = 102A, which exceeds VCTMP's 60A maximum. For this motor, Class J or Class R time-delay fuses with higher current range are required. VCTMP is not suitable.

The VICFUSE VCTMP is a time-delay, current-limiting Class CC fuse rated 600V AC and 600V DC, built to UL 248-4, with the Class CC series covering current ratings from 0.1A to 30A. For higher ratings from 35A to 60A, the Class CD series is designed according to UL 248-18, with interrupt ratings of 200kA at 600V AC and 50kA at 600V DC. It excels at motor branch circuit protection per NEC 430.52, serving small motors through 60A with the Class CC 300%/400% multiplier advantage over standard dual-element fuses. 

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