Anyone involved with mission critical facilities understands that operating a data center is expensive. As energy and power costs rise, typical data centers pay millions of dollars in power bills in addition to other equipment and IT costs. The more data is used — from emails, to streaming video, to the internet, monitoring, security, etc., — the higher the cost of data center operations.

While data centers address the burden of increased operational and power expenses, there are ways to utilize infrastructure changes to allow for savings. One such strategy — used world over and only recently entering the U.S. market — is the use of low voltage UL approved Form 4b Type 7 design switchgear. With space a finite resource for data centers, every square foot consumed by gear in the power chain takes away from revenue-generating IT equipment. U.S. data center operators can better utilize their available space using Form 4b Type 7 design’s compact, fully compartmentalized and robust switchgear option for mission critical applications. Furthermore, this allows data centers to invest in superior power systems, system fault resilience, and enhanced operator safety. And with more space allotted to production, the more revenues can be generated from the facility.

To understand why this design is just entering the U.S. market, we need to look at the history of its evolution.


The two predominant electrical standards for the world have been: the International Electro-technical Commission (IEC) used throughout Europe and the National Electric Manufacturers Association (NEMA) used primarily in the United States. Both of these standards, developed from different design philosophies, emerged from the post-World War II Europe and U.S. experiences.

The U.S. emerged from the war as an industrial giant with very few challengers on the world stage. While Europe, by contrast, was depleted of both natural and human resources

Europe, by necessity, used its limited resources with great care. Out of this necessity arose an application-oriented design philosophy focused on personal safety, and elimination of potential hazards. As mentioned earlier, human resources were in as much demand as physical resources in Europe, which gave birth to such design innovations as: finger safe protection, compartmentalization, insulated Busbars, and others.

Also, as each country developed its own standards — the British Standard (BS) in England and its former colonies, VDE in Germany and other individual country standards — IEC became the preferred process and methodology of combining these standards under one umbrella.

By contrast, the U.S. had vast natural and human resources as the human casualty in the war was far less than that in Europe. When nearly eight million service men and women returned to the U.S., they were ready to work, and work they did. The post war production in the U.S. was unlike anything the world had seen up to that point. Robust electrical and mechanical designs emerged — in many cases over designed for the application.

Where Europe focused on the application and personal safety, the U.S. focused on training of personnel and a strong design philosophy that generated products that would perform under the most extreme duress and for years beyond their anticipated life spans.

In the late 1990s, with the expansion of the global economy, both NEMA and IEC recognized the need to harmonize the standards and formed what became known as the Technical Advisory Groups (TAG) which worked closely to align the different standards. The TAG teams made a great deal of progress in areas like industrial control, automation, instrumentation, and circuit breaker technology.

During this period and up until the present day, one area of design continued on the divergent paths; low voltage (LV) electrical switchgear. While in the U.S. the LV switchgear has been primarily driven by the UL 892 and 1558 standards, EMEA pursed the IEC-609349 for low voltage switchgear. There are significant design differences, but not necessarily in performance. Both standards are safe and suitable for the U.S. market however, you would rarely see a UL891 product used in areas of the world where IEC is the dominant standard.

The key differences are expressed in personal safety, footprint, and component segregation. For the purposes of this article, we will focus on the UL891 standard as compared to IEC-609349 Form 4b Type 7.

The BEAMA Guide to Forms of Separation – Low Voltage and Controlgear Assemblies to BS EN 61439-2, published in July 2011, states, “The principle reason for separating an assembly is to facilitate the access to a part of the assembly whilst other parts may remain energized and in service. Whilst, in general, separation does not improve the electric performance of the assembly it does provide:

• Protection against contact with live parts belonging to the adjacent functional units.

• Protection against the passage of solid foreign bodies from one unit of an assembly to an adjacent unit.”

Due to the design differences, a legacy UL891 switchboard would not be acceptable for use by a customer in EMEA and would not be able to comply with IEC standards.

However, it is possible for an IEC Form 4b Type 7 to comply with UL891.

But it’s no small feat. The certification process for UL is rigorous and requires extensive preparation, documentation, and testing.

In order to understand the differences between a legacy UL 891 product and the UL certified Form 4b Type 7 product, let’s take a look at the principal design features of each product.


One of the key design differences between these two designs is the physical size of the unit. Table 1 provides a comparison between the legacy UL891 gear (black) and UL certified Form 4b Type 7 (red).

Data center construction techniques have evolved over the years to include many design concepts including modular buildings and skid-mounted products that are prepared in a factory setting for deployment in the field. Regardless of the design, space in the data center is always at a premium, and the more space that can be allotted to production, the more revenue can be generated from the facility.

The UL certified Form 4b Type 7 product offers significant and positive impact by reducing the amount of space required for this component of the power chain.

Another distinguishing feature of the UL certified Form 4b Type 7 switchgear is in the segregation of components. In legacy UL891 construction the individual components within a single vertical section are open — as illustrated in Figures 1 and 2.

The open construction of the typical UL891 product allows a fault in a single component to affect other components in the same vertical structure. With this design, there is very little isolation of components to prevent an electrical arc from travelling through the switchboard damaging other components and needlessly affecting the operation of large parts of the data center.

By contrast, the UL certified Form 4b Type 7 product provides a high level of segregation of:

• Incoming line connections

• Horizontal busses are completely isolated

• Vertical busses are isolated from the horizontal bus and circuit breaker compartments

• Circuit breakers are in an individual compartment and isolated from the other components

• The load side connection to the distribution circuit breakers are isolated resulting in a safer method for connecting the load

• The instrumentation compartments are totally segregated and protected from other components in the switchboard (Figures 1 and 2).

The segregation of components is critical to the design and performance of the UL certified Form 4b Type 7 equipment. Through compartmentalization, a data center can achieve a higher level of performance and reduce downtime due to human error or a component failure, such as a fault induced in a single circuit breaker.

An important advantage of the UL certified Form 4b Type 7 equipment is arc containment. Arc flash calculations are based on a number of different factors and there are very few products that can claim they are completely arc flash safe. Those that claim this are generally cumbersome to work on and come with a very high price tag.

The UL certified Form 4b Type 7 equipment provides a level of containment that can help reduce the damage from an electrical arc by containment and isolation. It offers a higher level of protection, based on the inherent design, at a reasonable cost and provides much better human protection for personnel that work on the equipment.

Additionally, the amount of PPE required may be reduced due to the inherent design features of the UL certified Form 4b Type 7 equipment.

In summary, the competitive advantages of a UL certified Form 4b Type 7 design — in comparison to legacy UL891 product available on the market today — offer:

• A more compact footprint

• A higher level of protection for internal components

• A higher level of human protection

• Better arc flash characteristics

More importantly, in considering rising data center operations cost, the UL certified Form 4b Type 7 achieves all of these functions at a price point equal to, or better than, the legacy UL891 design.

Data center operators considering their operational costs should explore the options offered by Form 4b Type 7 designs and the increased safety and decreased downtime advantages for their data center.