UL 508A PDF

1 Scope

1.1 These requirements cover industrial control panels intended for general industrial use, operating from a voltage of 1000 volts or less. This equipment is intended for installation in ordinary locations, in accordance with the National Electrical Code, ANSI/NFPA 70 and where the ambient temperature shall be between 5°C (41°F) and 40°C (104°F), unless marked with an ambient temperature rating.

1.2 These requirements also cover industrial control panel enclosures and industrial control panels primarily intended for flame safety supervision of combustible fuel type equipment, crane or hoist control, service equipment use, marine use, air conditioning and refrigeration equipment, equipment for load management applications, fountain control, irrigation equipment control, and for control of industrial machinery including metalworking machine tools, power press controls, and plastic injection molding machinery. Also covered are industrial control panels intended for control of permanently installed electrical equipment for aquatic playgrounds, permanently installed electrical equipment associated with commercial water park rides, wave pools and similar installations, and permanently installed electrical equipment associated with commercial and large residential swimming pools and in-ground spas.

1.3 This equipment consists of assemblies of two or more power circuit components, such as motor controllers, overload relays, fused disconnect switches, and circuit breakers, or control circuit components, such as pushbuttons, pilot lights, selector switches, timers, and control relays, or a combination of power and control circuit components, with associated wiring, and terminals. These components are mounted on, or contained within, an enclosure, or are mounted on a sub-panel.

1.4 An industrial control panel does not include an evaluation of the controlled equipment such as motors, heaters, lighting, and other loads connected to power circuits. Unless specifically noted on the wiring diagram of the industrial control panel, an industrial control panel does not include equipment mounted remotely from the panel and connected via a wiring systems or equipment field installed on or within the industrial control panel.

1.5 An evaluation of the adequacy of the controls and protective devices contained in an industrial control panel for supervision and proper functioning of the controlled loads or equipment is not covered by the requirements in this standard. Such evaluations are covered by the standards applicable to the complete piece of utilization equipment.

1.6 The evaluation of a pre-fabricated building, structure, or platforms supplied with industrial control panels are not covered by the requirements in this standard.

1.7 Fire pump controllers are covered by the Standard for Fire Pump Controllers, UL 218.

1.8 Equipment intended for use in hazardous locations, as defined in the National Electrical Code, ANSI/NFPA 70, are covered by the Standard for Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, UL 1203.

1.9 Industrial control panels incorporating intrinsic safety barriers and intended for connection to circuits residing in hazardous locations are covered by the Standard for Industrial Control Panels Relating to Hazardous (Classified) Locations, UL 698A.

1.10 Motor control centers, including motor control center sections and units, or equipment intended for field installation into a motor control center are covered by the Standard for Motor Control Centers, UL 845.

1.11 Assemblies of electrical control units or equipment containing electrical control units for fire-protective signaling systems are covered by the Standard for Control Units and Accessories for Fire Alarm Systems, UL 864.

1.12 A freestanding assembly of overcurrent protective devices and busses for control of electric light and power circuits or equipment intended for field installation in dead-front switchboards shall be evaluated to the Standard for Switchboards, UL 891.

1.13 Equipment intended to supply automatic illumination, power, or both, to critical areas and equipment essential to safety of human life is covered by the Standard for Emergency Lighting and Power Equipment, UL 924.

1.14 Control equipment for use with swimming pools and spas is covered by the Standard for Electric Spas, Equipment Assemblies, and Associated Equipment, UL 1563.

1.15 Portable control panels containing switches, overcurrent protection, and cord connected via attachment plugs and receptacles for use at carnivals, circuses, fairs, exhibition halls, motion picture and television studios, theaters, construction sites and similar locations are covered by the Standard for Portable Power-Distribution Equipment, UL 1640.

1.16 Equipment for the control of fuel cells, photovoltaic systems, or utility interactive systems are covered by the Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources, UL 1741.

1.17 Enclosures or pedestals containing terminals for connection of power circuit conductors are covered by the Standard for Termination Boxes, UL 1773.

1.18 Emergency alarm equipment or control panels containing emergency alarm equipment are covered by the Standard for General-Purpose Signaling Devices and Systems, UL 2017.

1.19 Equipment for gas or vapor detection or control panels containing gas or vapor detection equipment is covered by the Standard for Gas and Vapor Detectors and Sensors, UL 2075.

1.20 Control panels containing predominately communication equipment, such as telephone equipment and intended for installation in accordance with Chapter 8 of the NEC, is evaluated to the Standard for Information Technology Equipment – Safety – Part 1: General Requirements, UL 60950-1.

1.21 Control equipment intended for use in physical access control systems, which provide an attended or unattended means of monitoring or controlling traffic through portals of a protected area for security purposes; or in key management systems, which regulate or control access to the use of a device by electrical, electronic or mechanical means, are covered by the Standard for Access Control System Units, UL 294.

1.22 Electrically operated or mechanically operated control equipment or enclosures intended for theft deterrent or warning purposes, such as detectors, security containers or alarms for merchandise or property, are covered by the Standard for Antitheft Alarms and Devices, UL 1037.

1.23 Equipment primarily intended to energize or de-energize electrical loads to achieve the desired use of electrical power is covered by the Standard for Energy Management Equipment, UL 916. Such equipment is intended to control electrical loads by responding to sensors or transducers monitoring power consumption, by sequencing, by cycling the loads through the use of preprogrammed data logic circuits, or any combination thereof.

1.24 Control panels, control units, and other various electrical circuits employed within a control circuit device intended for support functions, maintain operation and limiting safety control features for use in a Stationary Engine Driven Assembly or similar power production equipment (generator) control applications are covered by the Standard for Controllers for Use in Power Production, UL/ULC 6200.

1.25 Industrial control panels intended for control of elevators, dumbwaiters, escalators, moving walks, inclined lifts, and associated equipment are evaluated to the requirements contained in ANSI/ASME A17.1, American National Standard Safety Code for Elevators and Escalators, and ANSI/ASME A17.5, Elevator and Escalator Electrical Equipment.

1.26 An assembly of overcurrent protective devices and busses for control of electric light and power circuits, provided as part of an industrial control panel, shall be evaluated to the Standard for Panelboards, UL 67.

1.27 Equipment or assemblies intended solely for providing ground fault protection are covered by the Standard for Ground-Fault Circuit-Interrupters, UL 943, or the Standard for Ground-Fault Sensing and Relaying Equipment, UL 1053.

Summary of Topics

This revision of ANSI/UL 508A dated June 26, 2025 includes the following changes in requirements:

– Limits to Control Circuit Voltages; 66.12.1 and 66.12.2

– Need for Emergency Stop Function; 66.11.2

– Disconnecting Means – Industrial Machinery; 66.6.1, 66.6.1A, Table 52.1

– Correction to Table SB4.1 – Controllers Rated 601 – 1000V

– UL 1059 Terminal Block Requirements; 28.2.1

– Overload Protection for Group Motor Applications; 31.4.1

– Terminals for Motors or Motors and Other Loads; 28.3.3

– Correction to SB4.2.2(b)

– Connection Means for Single Port Surge Protective Devices; SB4.2.1

– Alternate Class 2 Sources; 44.1.5

– Location of Ventilation Opening; 21.2.2 and Figure 21.1

– Additional Insulating Barrier Materials; 12.2

– Addition of GPO-2 and GPO-3 as Insulating Materials; 13.2, Table 13.1

– Semiconductor Fuses and Fuseholder Markings; 2.24, 30.3.4, 31.1.3, 31.3.2, 31.3.5, Table 52.1, 56.1 and 56.2

– Revisions to UL Component Standards; 30.1.4 – 30.1.6, 31.1.1, 31.1.4, 31.1.7, 31.4.3, 32.1.3, 33.1.1, 33.1.3, 33.7.1, 34.1.1, 42.3.1, 45.1.1, 46.1.1, 90.4.1 and 90.4.2

– Clarification of Locked Rotor Current Ratings for Disconnected Switches; Table 30.1 and Table 30.2

– Addition of Reference to UL 60335-2-40; 26.3.1

– Revision to 26.1.1 – Enclosure Environmental Control Devices

– Addition of Requirements for Voltage Detection Devices; 2.1A, 2.1B, 2.42A, Section 36.6, 75.8.5 and Appendix A

– Exclusion of Current Limited OCPD Drives; SB4.3.2 and SB4.3.3

– Clarification of Note “b” in Table 52.1

– Eliminate Exception for One-Port SPDs; SB4.2.1

– Panels Not Covered by the Scope of UL 508A; 1.27

– Formatting Correction to Table 19.2; Table 19.1, Table 19.2A, and 19.3

– Pipelines, Tubing or Devices for Handling Air, Gasses or Liquids; 18.2A – 18.2D, and 18.6 – 18.8

– Wiring Ferrules; 29.3.6 and Appendix A

– Field Provided Components; 60.3

– Addition of Requirements for Instrument Transformers; 43.1.1 and Section 47.5

– Power Supplies in a Power Circuit; 35.4.1.1, 35.4.1.2 and Sections 35.5 and 35.6

– Optical Fiber Cables; 38.1.2 and Appendix A

– Correction to 21.3.4

– Special-purpose Solid-state Overcurrent Protectors; 40.1.3A, 43.1.3, 44.1.5 and Appendix A

– Addition of Voltage Indicators and Voltage Test Point Devices; 66.6.1

– Wiring of an Oversized Variable Speed Drive; 28.3.5, 29.6.3 and 34.2.3