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UL 891 – An Introduction

What is UL 891?


UL 891 is a safety standard developed by UL Solutions (previously Underwriters Laboratories) for switchboards rated at 1000 V or less. It is also intended for switchboards that have short-circuit currents of less than 200,000 amperes. UL 891 is created to function in parallel with the National Electric Code (NEC) and NFPA 70 in the US, the European code IEC 60364, and the Canadian Electrical Code, Part I (CE Code, Part I).


Like other UL standards, the UL 891 safety standard is drawn up and updated to give suppliers, contractors, designers, and end users a common set of minimum standards that govern the building, testing, and usage of electrical switchgear assemblies. UL 891 switchgear is a crucial part of electrical distribution systems, as it’s used to control, protect, and isolate circuits and equipment. Effective UL 891 switchgear is necessary to protect personnel and equipment from electrical faults, which can endanger health and cause damage to equipment. They also power down equipment and circuits for repair or maintenance.


Using UL 891 switchgear ensures the expected safety measures have been met through the construction of the equipment and components used, which delivers several benefits for the end-user. In this blog, we’ll discuss what the UL 891 standard outlines and its impacts on electrical switchgear use. 


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What is covered in UL 891?


UL 891 applies to low-voltage switchboards, and in the context of the standard, “switchboard” refers to dead-front switchboards, i.e., those without any exposed live parts on the front. Both indoor and outdoor switchgear assemblies are covered in UL 891, along with the requirements, components, and testing for:


  • Low-voltage metal-enclosed switchgear

  • Low-voltage air-insulated switchgear

  • Low-voltage power circuit breaker switchgear

  • Low-voltage metal-clad switchgear


The important role that switchgear plays in ensuring safety for operators and equipment, as well as energy efficiency and limiting downtime, means that UL 891 switchgear needs to be built to a very high level of quality. The standard includes sections about:


  • Rated voltages

  • Short-circuit current ratings

  • Rated peak withstand current

  • Rated conditional short-circuit current

  • Rated fused short-circuit current

  • Instructions for installation, operation, and service

  • Markings (for safety and direction)

  • Normal and special service conditions

  • Mechanical design

  • Types of enclosure and degrees of protection

  • Protection against electric shock

  • Electrical connections inside an assembly

  • Switching devices and components within assemblies

  • Testing specifications


The long list of specifications is important for ensuring the safety and reliability of UL 891 switchgear, and allows designers, fabricators, and end-users to have greater clarity on the switchgear’s construction, installation, and use. Achieving compliance with the standard means that all parties know the UL 891 switchgear has met the criteria for testing and evaluation expected of it.


It is also important to note what is not covered under UL 891, namely:


  • Live-front switchboards

  • Switchboards with short-time current ratings

  • Preset and dimmer control (theater) switchboards

  • Railway control or electrification switchboards

  • Constructions solely intended to receive motor control center units

The Value of UL 891 Switchgear


Improved Safety


One of the most important roles of UL 891 switchgear is identifying electrical faults and isolating faulty circuits. This helps shield humans from coming in contact with electrified equipment or electrical arcing and suffering electrocution. Switchgear also limits short circuits and other hazards that can cause catastrophic damage to motors and other equipment. This is achieved by ensuring a minimum standard for construction, from the components used, such as circuit breakers and fuses, up to the insulation systems and enclosure design used for the switchgear.


Enhanced Energy Monitoring and Control


Energy efficiency is becoming an increasingly important metric for industrial and civil engineering. By creating a comprehensive framework for design, construction, and component use, UL 891 switchgear can be built using energy-efficient designs. It can also incorporate advanced monitoring and control equipment, such as IoT sensors, which can inform centralized teams about energy usage across the premises.


Regulatory Compliance


Adhering to applicable health and safety legislation minimizes operational and business risk. Ensuring compliance with standards such as UL 891 shows that every effort was made to maintain the highest expected levels of care and safety in the workplace, limiting potential liability. Regulatory compliance is also important when applying for many tenders and government contracts.


Reducing Downtime


Circuit overloads can cause catastrophic damage to certain equipment. Even at lower levels of impact, the overheating associated with electrical faults can require repair. This necessitates equipment downtime, backing up production, and reducing returns on an asset and lost labor hours. UL 891 switchgear effectively identifies faulty currents, isolates them, and switches loads to working circuits. High-quality switchgear can also make it easier for maintenance teams to power down certain equipment for scheduled servicing, which reduces how long the equipment is out of commission. 


Low voltage switchgear

Get Compliant with Enercon


Electrical switchgear plays an important role in electrical distribution systems by allowing operators to control, protect, and isolate circuits and equipment. UL 891 is a safety standard for dead-front switchboards rated at 1000 V or less. UL 891 gives designers, fabricators, and users a comprehensive outline for building, testing, and using low-voltage switchgear. 

Using UL 891 switchgear delivers several benefits, including improved safety for personnel and equipment, enhanced energy monitoring and control, achieving regulatory compliance, and reducing equipment downtime.


At Enercon, we have years of experience building UL 891 switchgear to custom or general designs, helping our customers improve safety, achieve compliance, and reduce risk. To learn more about how we can deliver UL 891 switchgear for your next project, contact us today.

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