Chapter 13, Problem 1RQ

Explain how the NEC® and Underwriters Laboratories categorize general-use snap switches. (Objective 13-1)

To determine

Categorization of snap switches by NEC and Underwriters Laboratories.

Explanation of Solution

General use snap switches are defined as the switches which are used for controlling the equipment and preventing arcing of the switch due to the ignition of the external atmosphere. These switches can be installed in device boxes or used in the wiring system.

According to NEC and underwriters laboratories, these switches are categorized into two types.

1. Alternating current general use switch − As their name suggests these switches can be used only for a circuit having alternating current flowing through it. These switches control the following values as per section 404.14(A) of article number 404 of NEC controls.
• Motor loads −The motor loads whose rating is less than 80 % of the ampere rating of the switch at the given voltage.
• Lamp load − A load of a lamp having filament of tungsten and having a rating less than the rating of the switch at 120 V.
• Resistive and inductive loads − Loads if a rating is less than the ampere rating of the switch at the voltage at which the switch operates.
2. Direct current or alternating current general use switch − These switches can be used for the circuits having alternating current or direct current flowing through it. These switches control the following values as per section 404.14(B) of article number 404 of NEC controls.
• Inductive loads −Its values are controlled if the rating is less than 50 % of the ampere rating of the switch at the given voltage.
• Lamp load − A load of a lamp having filament of tungsten is controlled if it has a rating less than the rating of the switch at applied voltage.
• Resistive load− It is controlled if its rating is less than the ampere rating of the switch at the voltage at which the switch operates.