Short Circuit Current Ratings for Combination Motor Controller Components

General

Article 409 of the National Electrical Code (NFPA 70) requires industrial control panels to be marked with an SCCR. As specified in the National Electrical Code (NEC), UL 508A Supplement SB, the Standard for Industrial Control Panels, provides an accepted method for determining the SCCR of the control panel. Industrial control panel manufacturers can use the spreadsheets below for guidance. They are intended for those manufacturers that purchase the discrete components and assemble combination motor controllers within their panels to achieve a combination SCCR that is higher than the lowest-rated individual component.       

Use

The combinations listed in the spreadsheets below may be applied in a manufacturer’s listed industrial control panel without further evaluation or specific documentation in the manufacturer’s UL Solutions procedure pages.

The spreadsheets cover the application of individual components, including a disconnecting means, an overcurrent protective device, motor controller and motor overload protection, and as a combination motor controller with specified ratings, including an SCCR. Each individual component is listed or recognized to the requirements for the applicable component standard.

The specified ratings for the combination motor controller may be applied to the end-product equipment only when all of the specific components listed are provided in the end-product equipment and installed according to any applicable conditions of acceptability.

Components other than those identified in the combination motor controller and connected in the power circuit of the combination motor controller will require additional evaluation.

See below for a detailed explanation of the tabular information contained in the spreadsheets:

I. Combination type / ID number

II. Individual component information

III. Combination motor controller information

I. Combination type / ID number

The letter designating the construction type of the combination motor controller, as defined in UL 508 or UL 60947-4-1, the Standards of Safety for Industrial Control Equipment, comprising specific components are described below:

II. Individual component information

Identification of all components of a combination motor controller

Component Type: Identifies each type of component provided in combination motor controller:

Company name and model number: Identification of the specific component in the combination motor controller.

Individual component ratings:

• HP: Horsepower rating for component, if provided
• kA: Marked short-circuit current rating (SCCR) on individual component
• Max Amps: Maximum ampere rating of individual component
• V: Voltage rating of individual component

III. Combination motor controller information

Identifies information required to install combination motor controller in end product:

Combination ratings: Ratings for combination motor controller:

• kA: Maximum short-circuit current rating (SCCR) for combination motor controller
• V, Ph: Maximum voltage rating and number of phases for combination motor controller
• HP or Maximum Amperes: Maximum horsepower or current at the corresponding voltage rating for combination motor controller

Conditions of acceptability

Unless specified otherwise in the individual recognitions, consider the following conditions of acceptability when these components are employed as a combination motor controller in the end-use equipment.

Specific conditions of use: Number refers to specific condition of use number as defined and applicable to the combination motor controller.