Issue link: https://cp.revolio.com/i/457819
14 | THE DATA CENTER JOURNAL www.datacenterjournal.com most extreme duress and for years beyond their anticipated life spans. e expansion of the global economy in late 1990's led to NEMA and IEC's recognition for unified standards. e Technical Advisory Groups (TAG) was formed to align the different standards in areas like industrial control, automation, instrumentation, and circuit breaker tech- nology. However, the low voltage electrical switchgear design took divergent paths. In the U.S. the low voltage switchgear is primarily driven by the UL 891 and UL 1558 standards while in EMEA the IEC- 609349 for low voltage switchgear took precedent. e significant design differ- ences do not alter the performance levels and while both standards are safe and suitable for the U.S. market, rarely a legacy UL891 product is used in areas of the world where IEC is the dominant standard. e key differences are in personal safety, footprint, and component segregation. Legacy uL891 Designs vs. uL/iec form 4B type 7 e Low Voltage and Control gear Assemblies to BS EN 61439-2, published in July 2011 issue of the BEAMA Guide to Forms of Separation, states, "e principle reason for separating an assembly is to fa- cilitate the access to a part of the assembly whilst other parts may remain energized and in service. Whilst, in general, separa- tion does not improve the electric perfor- mance 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." e design differences make a legacy UL891 switchboard unacceptable for use by a customer in EMEA and not in compliance with IEC standards. While IEC Form 4b Type 7 complies with UL891, the process for UL is rigorous and requires extensive preparation, documentation and testing. e differences between a legacy UL 891 product and the UL certified Form 4b Type 7 product are the principal design features of each product which include: • e physical size of the unit – e UL certified Form 4b Type 7 has 39" (Depth) 89" (Height) and is Modu- lar in 4" increments • e significant and positive im- pact in reduced amount of space required for this component of the power chain. • e segregation of components with legacy UL891 construction allowing individual components within a single vertical section to be open -- as illustrated below. e open construction allows a fault in a single component to affect other components in the same vertical struc- ture. 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 affect the operation of large parts of the data center. In contrast, the UL listed Form 4b Type 7 design offers a high level of segrega- tion of: • Incoming line connections • Completely isolated horizontal busses • Isolation of vertical busses from the horizontal bus and circuit breaker compartments • Circuit breakers - in an individual compartment – are isolated from the other components • e load side connection to the distribution circuit breakers are isolated for a safer connection to the load • e instrumentation compartments are totally segregated and protected from other components in the switchboard. Critical to the design and perfor- mance of the UL891 listed Form 4b Type 7 equipment are: • e component segregation - the compartmentalization allows a data center a higher level of performance and reduced downtime due to hu- man error or a component failure, such as a fault induced in a single circuit breaker. • Arc containment is a major ad- vantage of the UL listed Form 4b Type 7 equipment as it helps reduce damage from an electrical arc by containment and isolation. It offers higher level of human protection based on the inherent design that also reduces the amount of required PPE. Note: 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 – without being cumbersome or highly costly. When considering the rising data center operations cost, U.S.-based mission critical facility operators should consider power infrastructure options to achieve crucial functions cost-effectively. is would in turn offer increased safety issues and decrease downtime advantages. n about the author: John Day is VP of Sales and Marketing for Anord Critical Power which offers an innovative, UL approved Form 4b Type 7 design AMS switchgear in the U.S. market.