Industrial Control Panel (ICP)

An industrial control panel must meet various safety requirements—depending on its application, intended use, and environmental conditions—in order to be connected to the U.S. power grid. A corresponding UL label serves as recognized proof that the control panel has been tested and certified in accordance with the relevant standards.

What is an industrial control panel?

An Industrial Control Panel (ICP) refers to an industrial control cabinet or industrial control panel. According to the National Electrical Code (NEC), it is an assembly consisting of at least two components that are part of a power or control circuit, or a combination of both. The definition covers systems with a maximum rated voltage of 600 volts.

Legal Requirements and Standards

Specific safety regulations and technical standards apply to Industrial Control Panels (ICP) in North America. In the United States, particular attention must be paid to the requirements of the National Electrical Code (NEC), including Article 409 and Section 110.3(B) of NFPA 70.

Control cabinets that do not comply with applicable regulations or lack sufficient proof of conformity may be rejected by the competent testing authorities, the Authorities Having Jurisdiction (AHJ). This can result in significant additional costs for manufacturers.

Among the most important technical standards are UL 508A for industrial control panels in the United States and CSA C22.2 No. 14 for the Canadian market. These standards form an essential foundation for the safe design and certification of industrial control panels.

UL Certification Program for Industrial Control Panels

Underwriters Laboratories (UL) is one of the leading testing and certification organizations for the North American market. Through the Industrial Control Panel Shop Program (ICP Program), UL offers control panel manufacturers the opportunity to mark both custom-built and mass-produced control panels in accordance with applicable UL requirements.

Once successfully accepted into the program, qualified manufacturers may independently affix the corresponding UL marks for the U.S. and Canada to their control cabinets. This is contingent upon the products meeting the specified requirements and the manufacturers complying with regular UL inspections. However, this does not make them independent certification bodies.

In Germany, only a limited number of control cabinet manufacturers have the necessary authorization to participate.

Certification Requirements for Industrial Control Panels

The UL Mark indicates to regulatory agencies, designers, and certification bodies that an Industrial Control Panel (ICP) has been tested and certified in accordance with the relevant safety standards. The ICP program simplifies the path to UL certification for manufacturers while also allowing for flexible control cabinet design. Selecting suitable components is crucial for a UL-compliant design. Whenever possible, UL-listed components should be used.

Industrial control panels intended for the Canadian market can also obtain UL certification, provided they meet the applicable Canadian requirements. Agreements between UL and the Canadian Standards Association (CSA) facilitate the recognition of certain tests and certifications. Similarly, control panels for the U.S. market can obtain the appropriate CSA certification.

Different UL and CSA certification marks are available for both markets, indicating the respective scope of the certification. The following overview shows the corresponding marks.

Design and Construction of an Industrial Control Panel

The development of an Industrial Control Panel (ICP) begins with the definition of all technical specifications, operational requirements, and relevant standards. Based on this, detailed circuit diagrams are created that depict, among other things, the wiring, electrical circuits, control components, and other technical details. These diagrams, also known as wiring diagrams, form the basis for the subsequent design and manufacture of the control cabinet.

When designing and configuring an industrial control panel, various technical and safety-related aspects must be taken into account. The most important criteria include:

• Housing and Space Requirements

The selection of the appropriate control panel enclosure depends on the specific operating and environmental conditions. Depending on the application, the control panel enclosure must meet certain requirements regarding protection rating, dimensions, and durability.

• Wire Sizing

When sizing the wiring, particular attention must be paid to the load currents that will occur. The conductor cross-section must allow for safe current transmission, while the associated overcurrent protection must be matched to the cable sizing. This is intended to prevent excessive heating of the cables and potential fire hazards.

• Component Types

When selecting suitable components, the required electrical ratings and dimensions play an important role in addition to their function. Voltage and current-carrying capacity, in particular, influence the sizing of components. In addition, the applicable UL standards contain specific requirements regarding wiring materials, conductor markings, and required conductor cross-sections.

• Control Components

Various components, such as relays, time relays, and terminal blocks, are used to control an industrial control panel. When selecting these components, it is recommended to use components that are as simple and reliable as possible and that meet the functional and safety requirements.

• Circuits

Control circuits determine the operations and functions of the connected electrical components. For safety reasons, they are often operated at a lower voltage than the main circuits. Control transformers (CPTs) or suitable power supplies are used to adjust the supply voltage to the required control voltage.

• Supply Manager

The sizing of the supply cables must be tailored to the expected electrical loads. In doing so, sufficient current-carrying capacity and the applicable safety requirements must be taken into account to ensure a reliable power supply to the control cabinet.

• Overcurrent Protection

The method of implementing overcurrent protection must be determined as early as the design phase. Depending on the system configuration, the required protective devices may be located inside or outside the control cabinet. If the cabinet is to be opened as infrequently as possible, a protective device accessible from the outside may be advisable. The specific design depends on the technical and regulatory requirements.

• Control Devices

Various elements are available for operating an industrial control panel, including pushbuttons, indicator lights, display instruments, switches, and modern touchscreen interfaces. Complex human-machine interfaces (HMIs) offer additional functions but often require additional hardware and software. A clear, user-friendly design that meets all operational requirements is crucial.

If an emergency stop function is required for the machine or system, it must be implemented in accordance with applicable safety regulations. Red, mushroom-shaped pushbuttons with a yellow background and a locking function are frequently used for this purpose. The requirements of the U.S. Occupational Safety and Health Administration (OSHA) must also be taken into account in the safety-related design.

• Labeling

Clear and permanently legible labeling of all relevant wires, terminals, and components facilitates the installation, testing, and maintenance of the control cabinet. At the same time, it helps prevent errors during repair and maintenance work. The labels used must therefore be suitable for the respective environmental conditions and sufficiently resistant to damage or fading.