Should You Comply with Article 645 of the National Electrical Code
September 21, 2009

By Kevin Meyer, Syska Hennessy Group
Christopher Johnston, Syska Hennessy Group

Appeared in

A major consideration in the design of a data center is whether the Information Technology Equipment (ITE) space will comply with Article 645 of the National Electrical Code (NEC). Article 645 covers equipment, power supply wiring, equipment interconnecting wiring, and grounding of information technology equipment and systems. Chapters 1 through 4 of the NEC establish the mandatory minimum requirements for electrical installations in typical facilities. If we comply with Article 645, we can ignore some of the most burdensome of the mandatory requirements in Chapters 1 through 4.

To assist you, we have identified the major differences in design, planning and operation between data centers that comply with Article 645 and those that do not comply. In this comparison we have utilized the 2008 version of the National Electrical Code that is enforced by most local authorities with jurisdiction.

Non-Article 645-compliant space headaches
A non-Article 645-compliant space must meet the requirements of Chapters 1 through 4. These requirements are most relevant and burdensome in an ITE space with a raised floor used as an air plenum, and limit the electrical system flexibility and maintainability desired in ITE spaces.

Article 645-compliant ITE space reduces requirements
These are the pluses that increase the electrical system flexibility and maintainability desired in ITE spaces. Note that these pluses do not include increased availability (uptime) of the computer equipment.

Article 645 sounds good. What's the catch?
Like most things in life, Article 645 is not a free lunch. The writers of Article 645 are saying, "OK, we will let you ignore some of the most burdensome requirements of Chapters 1 through 4, but you will have to pay a price." The price is requirements that increase fire safety and speed of shutdown in an emergency. These are the minuses that you must consider when evaluating the pluses.

In summary, complying with Article 645 allows for:

This makes for easier installation and modifications to the IT equipment that changes often. It is not unusual for many ITE room operators to refresh their computer hardware every three years, so the equipment comes and goes daily. However, the availability (uptime) of the electrical and mechanical systems is lessened because of the requirements for an EPO system and automatic shutdown of HVAC systems upon detecting smoke under the raised floor. The decision gets back to a value judgment that you and your client need to make together.

Kevin Meyer is the project manager and principal of the Florida region for Syska Hennessy Group. He has over 10 years experience as an electrical consulting engineer of highly complex facilities. Kevin focuses on design efforts to achieve energy efficiency, reliability and flexibility, with an emphasis in emergency/redundant power critical to the function of a data center environment.

Christopher Johnston is a Vice President and Chief Engineer for Syska's National Critical Facilities Team, the head of Syska's Critical Facilities' Technical Leadership Council and a member of Syska's Green Critical Facilities Committee. He leads research and development efforts to address technical issues in critical and hypercritical facilities, and specializes in the planning, design, construction, testing and commissioning of critical 24/7 facilities. Johnston brings 38 years of engineering experience in the field. Johnston is also regular presenter at conferences such as Data Center Dynamics and the Uptime Institute.