Choosing the right standards for North America

All components in the panel shall be selected depending on the intended use in relation to their product testing standard. For example, Siemens SENTRON 3LD20 (manual motor controller) is well-known as physical switch disconnector and is often used as a main disconnect in the IEC world. It also looks quite similar as the SENTRON 3LD5-series and that can bring confusion.

However, for North America, the SENTRON 3LD20 cannot be used as a main disconnect or machine supply circuit disconnect. It has been tested and meets the UL 60947-4-1 standard (the successor of UL 508) as a manual motor controller. Please note that this type of product and certification allows the component only to be used in a branch circuit to safely disconnect a motor load in the field for maintenance work.

Now, if you are looking for the suitable component for a machine supply circuit disconnect (feeder circuit), then you have to look for a tested molded case switch, for example our SENTRON 3LD5-series, which are all UL 489 tested.

The main electrical code in the U.S. is the National Electrical Code (NEC), also known as NFPA 70, which governs all electrical building installations nationwide. Article 409 of the NEC outlines the basic requirements for installing industrial control panels in industrial buildings, specifying the necessary criteria. For detailed guidelines on designing and sizing an industrial control panel, the NEC refers to UL 508A as the appropriate safety standard. Adhering to this standard ensures compliance with the NEC.

Often, an industrial control panel is specifically designed to control industrial machinery, requiring consideration of NFPA 79, the Electrical Standard for Industrial Machinery, mentioned in Chapter 670 of the NEC. If the control panel is intended for hazardous locations, the NEC refers to UL 698A for industrial control panels in such environments.

The NEC references these standards because they are considered "state of the art."

As mentioned earlier, the NEC is the primary standard for electrical installations in the U.S. However, the version of the NEC you need to use can vary depending on the state where the industrial control panel will be installed.

Here is the NFPA adaptation of a map showing the different NEC versions in effect across various states. For example, Texas requires the 2023 version, while California allows the use of the 2020 version or newer. As you can see in the map from August 1st 2024, only Indiana and Kansas still accept the NEC 2008 version. Consequently, all previous versions of the NEC can't be used today in North America.

Our recommendation is to use the latest version of the NEC to ensure it is accepted in all states.

Get the latest information on the official NFPA website

In 2024, Restricted Access to Enclosures requirements were aligned with the requirements with the NFPA 79. A door locking system is not mandatory anymore, but our recommendation is to focus on the safety philosophy of the end user of your panel or industrial machinery, so that you can provide the best solution in agreement with your customer and the standards.

Further information can be found in the related control panel tip door interlocking.

Manual motor controllers that have been certified with “tap conductor protection” can be used as transformer protection or for safeguarding power supplies for control circuits as “supplementary protection” on the load side of a short-circuit protective device for motor loads. It should be noted that the entire control circuit will fail if the motor short-circuit protective device trips.

Single-phase 120 V receptacles with a rated current of 15 or 20 amperes in control cabinets for industrial machines must now be protected by a ground-fault circuit interrupter (GFCI) in accordance with UL 943 for personnel protection, regardless of the installation location or the enclosure’s degree of protection. This has been harmonized with NFPA 79 and therefore also applies to the electrical equipment of industrial machinery.