National Electrical Code 2005: Keeping it Simple

10/20/2004


By Chris Tapas, P.E.
President, Tapas Engineering Services PC
Chicago

Editor’s Note: This is the first installment in a regular monthly column that will cover significant new issues raised by the 2005 Edition of the National Electrical Code.

More than 3,580 proposed changes were submitted to the National Fire Protection Association (NFPA) to amend the 2002 National Electrical Code ( NEC ). What drives these changes are three concerns: life safety conditions, protection of property and important changes in technology. W hile the NEC itself does not have the authority of law, almost every jurisdiction in the United States adopts the NEC by reference in its building and fire codes.

Knowing the significant changes and how to put them into practice is perhaps the most important focus for the consulting engineer.

Starting point
Among the new or revised items in the 2005 NEC that have a significant impact on a consulting engineer is Article 110.26 - Spaces About Electrical Equipment. This change affects requirements for construction and tenant improvement projects. Article 110.26 deals with the requirements for entrances to work spaces housing large equipment, defined as “equipment rated at 1200 amperes or more shall require entrances at least 24 inches wide and 6.5 feet high at each end of the workspace.” The phrase “and over 6 feet wide in size” was removed from the physical size requirement citied in previous codes. The focus is being redirected to the force of the arc created by equipment of that ampere rating, not the physical size of the equipment.

What does this revision really mean and how does that translate into everyday application? This revision has a potential impact to the commercial developer/owner. The implication is each electrical room located on a floor with rentable space with a piece of electrical distribution equipment rated at 1,200 amps or more will require two means of egress and has the potential to impact the net rentable space on that floor. Each egress has specific architectural criteria that may require compliance such as opening into a corridor, creating a need to add new corridors, which will or can translate into additional non-rentable space.

Under previous code requirements, two means of egress were needed when using equipment rated at 1,200 amps or more over six feet in length. Now under the 2005 code, if the equipment is rated 1,200 amps or more, two means of egress are needed, regardless of length. Having two egresses will require more physical room to accommodate the additional wall space required for the second means of egress, thus potentially increasing the size of the electrical rooms. The potential revenue impact to an owner/developer is the electrical rooms located on floors with net rentable space, which are typically in the core of the building. These rooms do not conform easily to reconfiguration. Reconfiguring electrical rooms for this new requirement may create a potential for impacting the net rentable space in a building floor plate.

Most equipment rated 1,200 amps or more is usually located where there is a high concentration of mechanical equipment. The result is that distribution equipment at this rating is located in the main service electrical rooms, typically in basements and electrical rooms located on mechanical floors and penthouses. Electrical rooms located in these areas already have the required two means of egress or adding a second means of egress in these locations would have a minimal impact on the net rentable space, if any.

Additionally, commercial office buildings typically do not have a power requirement that would place a 1,200-amp distribution on every rentable floor. However, the need for a distribution point of this capacity may be required on intermittent floors or in locations of high power requirements such as computer rooms and kitchens.

Every code update gives the design professional the responsibility of learning the revisions and the potential impact on our clients and their business operations. Early identification of the revisions and their impact is in everyone’s best interest, in order that future projects can be planned and designed effectively.





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