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Demystifying UL Listings: Navigating Electrical Switchgear Standards

Every industry or premises in the United States that uses electrical equipment must meet specific regulatory safety standards, including the overarching National Electrical Code or NEC (NFPA 70), which is a general benchmark for electrical safety. However, there are more specific standards for certain equipment and situations. Underwriter Laboratories (UL), a globally recognized safety science company, created these standards.

Several UL codes apply to electrical switchgear, and navigating these can be complicated. Failure to adhere to relevant UL listings for electrical switchgear can put employees in danger, risk catastrophic damage to equipment, cause accidents such as fires that can lead to production downtime, and lead to litigation or compensation to affected parties.

Man looking at switchgear

Demystifying UL Listings for Electrical Switchgear

Below, we’ll demystify the UL codes for electrical switchgear to give you a rough idea of what each means and which listing applies to each element of switchgear design, installation, and operation.

UL 1558 - Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear

UL 1558 is a safety standard for metal-enclosed circuit-breaker switchgear assemblies with a maximum voltage of 600V AC. It details several minimum requirements for designing and constructing low-voltage switchgear, and operational safety performance limits. 

UL 1558 contains safety guidelines for:

  • Operator safety

  • Provision of disconnects

  • Dielectric withstand voltage

  • Spacings for components and wiring

  • Working space

  • Corrosion protection

  • Viewing panes

  • Temperature ratings

  • Markings

Interrupting devices such as low-voltage circuit breakers, switches, control equipment, instrumentation, metering equipment, protective equipment, and regulating equipment all must adhere to UL 1558. 

UL 891 – Standard for Safety for Switchboards

UL 891 covers the design and construction of electrical switchgear used to control, protect, and isolate electrical circuits and equipment in power distribution systems rated to 1000V or less. The standard covers both indoor and outdoor switchgear assemblies and includes:

  • Low-voltage power circuit breaker switchgear

  • Low-voltage metal-enclosed switchgear

  • Low-voltage metal-clad switchgear

  • Low-voltage air-insulated switchgear

The focus of UL 891 is to protect equipment and the electrical system from faults, which switchgear does by using circuit breakers and fuses to detect and isolate faults quickly. Along with material guidelines and the design and assembly of the switchgear, UL 891 also outlines the correct testing procedures for ensuring the switchgear is up to code.

UL 845 – Standard for Safety for Motor Control Centers

The UL 845 standard applies to motor control centers covered under the NEC/NFPA 70 and applies to motor control centers with short circuit currents rated not more than 1000V AC or DC and not exceeding 200,000 A RMS symmetrical or 200,000 A DC. 

Relevant motor control centers under UL 845 can contain, and are not limited to, the following:

  • Full voltage reversing or non-reversing motor control units

  • Solid-state industrial controllers

  • Reduced-voltage part-winding, wye-delta or auto-transformer motor control units

  • Feeder-tap units

  • Incoming-line equipment, such as fusible switches, isolation switches or circuit breakers

The standard is focused on defining how individual components are rated and tested for that rating as part of a specific motor control assembly. For UL 845, a compliance listing can only be given for the specific components for the applicable unit together.

UL 1008 – Standard for Safety for Transfer Switch Equipment

UL 1008 is for transfer switches connecting electrical loads from two different, often dissimilar, sources of power. An example would be equipment with power feeds from a public mains power source and an on-site generator. The transfer switch is relied on to detect power failure, identify the acceptability of the alternate power source, transfer the load, and then re-transfer back to the normal source when possible.

The UL 1008 standard specifies the criteria for testing a transfer switch's ‘withstand’ and ‘closing’ ratings. Achieving certification requires the manufacturer to show they have successfully tested the equipment and components of the transfer switch at its rated capacity. Examples of applicable testing for UL 1008 equipment include:

  • Operability

  • Endurance

  • Short-circuit current handling ability

  • Overload

  • Temperature rises

UL 6200 – Standard for Safety for Controllers for Use in Power Production

The UL 6200 standard was created to update the safety guidelines for control units used in power generation and utility synchronization. These have advanced significantly in recent years, especially regarding automatic controls, and aren’t sufficiently covered in other UL listings. The components and equipment covered include:

  • Starting controls

  • Fuel system controls

  • Engine speed controls

  • Generator paralleling controls

  • Synchronization controls

There are several component specifications necessary to meet the UL 6200 standard, including those for:

  • Switching devices

  • Disconnection and overcurrent protection devices

  • Solid insulating materials

  • Overload testing

Since UL 6200 is written with power production controls in mind, it also includes specific guidelines for safety circuits in control equipment, the software used in controls, engine start controls, and generator paralleling equipment.

Illustration representing UL switchgear in a lab setting

Build to UL Standards with Enercon

Underwriter Laboratories oversees numerous standards for the design, assembly, and operation of electrical equipment, including electrical switchgear and control panels. These UL listings are essential for ensuring safety standards across multiple industries and uses for this equipment. Due to the growth in new technologies, such as automatic controls, specific UL listings are created for smaller use case equipment and components whose usage or environment may differ from a standard scenario.

Each UL listing will lay out guidelines on the design and assembly of the equipment, components and materials that should be used and how these should be tested. Installing UL-certified equipment reduces the risk of hazardous situations, such as fire or electrical arcing, which cause danger to operators and equipment and can help minimize downtime and improve interoperability. They also help to ensure regulatory compliance, reducing organizational exposure to liability and litigation.

At Enercon, we design and assemble electrical equipment to meet both your needs and the relevant regulations, including low and medium-voltage switchgear (UL 891, UL 1558) and industrial control panels (UL 508A, UL 698A). To find out how we can deliver the electrical equipment solutions you need that will improve safety and reduce organizational risk, contact us today. 

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