What is the difference between UL 1558 and 891?

When it comes to electrical standards, UL 1558 and UL 891 are two common certifications that are often mentioned. While they both pertain to electrical switchgear, there are some key differences between these two standards.

UL 1558: A Brief

UL 1558 is a standard established by Underwriters Laboratories (UL), a global safety certification company. This standard focuses on low voltage metal-enclosed power circuit breaker switchgear assemblies. It sets out specific requirements for design, construction, testing, and performance of these assemblies. UL 1558 ensures that switchgear assemblies meet safety and operational standards to ensure reliability in electricity distribution systems.

UL 891: Understanding the Basics

UL 891 is another standard created by UL. Unlike UL 1558, which deals with power circuit breaker switchgear, UL 891 focuses on dead-front switchboards or switchgear assemblies that incorporate molded case circuit breakers. These switchboards are typically used in commercial buildings and industrial facilities to control and distribute electrical power. UL 891 aims to ensure proper installation, operation, and maintenance of these switchboards.

Key Differences between UL 1558 and UL 891

1. Scope: The primary difference lies in the type of switchgear each standard covers. UL 1558 focuses on metal-enclosed power circuit breaker switchgear, while UL 891 addresses dead-front switchboards or switchgear assemblies with molded case circuit breakers.

2. Testing Requirements: Both standards have their own specific testing requirements to ensure compliance. UL 1558 includes tests for short-circuit withstand, temperature rise, dielectric withstand, and more. UL 891 testing involves various procedures like temperature and current cycling, voltage withstand, and mechanical operation.

3. Applications: UL 1558 switchgear finds its applications in utilities, petrochemical plants, and other industrial settings where higher power distribution is required. UL 891 switchboards are commonly used in commercial buildings, hospitals, shopping malls, and similar facilities where lower power distribution needs are met.

4. Certification Labels: Each standard has its own certification mark to designate compliance. Switchgear assemblies that meet UL 1558 requirements are labeled with the UL 1558 certification mark, while those conforming to UL 891 carry the UL 891 certification label.

It is important to note that adherence to either of these standards ensures that switchgear or switchboards have undergone rigorous testing and meet necessary safety requirements. The choice between UL 1558 and UL 891 depends on the specific application and system requirements.