Which type of device is defined by UL as tripping at a fault current of 6mA or more?

• A. Class B
• B. Class A
• C. Class C
• D. Class D

Answer: (B)

The correct answer is Class A. Class A devices, as defined by Underwriters Laboratories (UL), are designed to trip when they detect ground fault currents of 6 milliamperes (mA) or more. This sensitivity is critical for safety, particularly in environments like residential areas, where a ground fault can present a significant risk of electric shock or fire. Class A devices are typically used in areas where there is a higher likelihood of human exposure to electricity, making their faster response to fault currents essential for preventing serious injuries.

In contrast, Class B and Class C devices have different tripping thresholds or applications that do not include this specific sensitivity to 6mA. Class D devices may also differ in functionality and specifications further, which places them outside the characteristics that define Class A devices. This emphasis on lower trip thresholds in Class A devices is part of a broader strategy to enhance electrical safety in various settings.