Type 1 and Type 2 coordination
To meet the need for greater harmonization in the North American market, the standards organization UL, together with representatives from industry, has harmonized the standard for industrial switchgear UL 508 with selected chapters of the IEC 60947 series of standards for low-voltage switchgear and control gear.
60947-1: Low Voltage Switchgear and Controlgear - Part 1: General Rules
UL 60947-4-1: Electromechanical Contactors and Motor-Starters
The latter is harmonized to the greatest possible extent with the IEC 60947-4-1 standard (contactors and motor starters - electromechanical contactors and motor starters), whereby the deviations for North America are set out in the UL 60947-4-1 standard. UL 60947-4-1 addresses the coordination between the Branch Circuit Protective Device and the motor starter, distinguishing between Type 1 or Type 2 coordination, and provides a method for evaluating the short-circuit performance of these devices.
According to UL 60947-4-1, the type of assignment defines the permissible degree of damage to a device after a short circuit. Component combinations must be selected according to the desired assignment type (1 or 2).
Some standards require that contactors and associated short-circuit protective devices are selected to meet the requirements of IEC 60947-4-1 for type 2 coordination, e.g. IEC/EN 60204-32 Electrical equipment of machines - Part 32: Requirements for hoisting equipment.
Labelling requirements for UL 508A listed industrial control panels
UL 508A:2018 requires a specific marking for industrial control cabinets with a high rated short-circuit current i.e. the SCCR is higher than the standard SCCR of the individual components.
Risk of Fire or Electric Shock – The opening of the branch-circuit protective device may be an indication that a fault current has been interrupted. All current-carrying parts and other components protected by this device should be examined and replaced if damaged. If burnout of a current element of an overload relay occurs, the complete overload relay must be replaced.
These markings are intended for service and maintenance personnel. For devices with type 2 coordination, the starter can be checked to determine whether it is damaged and can be used for further operation. On the other hand, devices of type 1 coordination should be replaced as recommended in the standard, since a thorough inspection of the components is usually not possible.