/images/NEC_button.jpg/images/southwire_100x70.jpg2002 NEC to Include Metric2002NECtoIncludeMetric.htmHere's a chance to influence the 2002 National Electrical Code (NEC). The NEC Metrication Task Group has developed proposed guidelines for the 2002 NEC code-making panels.
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2002 NEC to Include Metric

Power Cable Update: April 1999

Here's a chance to influence the 2002 National Electrical Code (NEC). The NEC Metrication Task Group has developed proposed guidelines for the 2002 NEC code-making panels. Your comments are invited. "NEC metrication is happening, but in compliance with NAFTA guidelines, Mexico, Canada and the U.S. will continue to use AWG and kcmil numbers as their primary wire and cable size designations," says Dave Mercier, applications engineering manager and a member of NEC code-making panels #6 and #8.

The metrication proposal (See box.) provides soft conversions, but does not add IEC-based metric wire sizes to the 2002 code. You can forward comments on the planned proposal to dave_mercier@southwire.com, or you can submit a proposal using the form in the back of the 1999 NEC. November 5, 1999, is the deadline for proposals. All proposals receive responses.

"The goal is to have metrication reflect the needs of the end-users," says Mercier.

The NEC Metrication Task Group Proposal

The NEC NFPA TCC Task Group on Metrication of the NEC plans to pursue the following course of action:

  • Express all units in SI units first followed by the equivalent inch-pound units in parenthesis. The intention is to leave the inch-pound units in the Code for an indefinite period; at least a generation.
  • Soft conversion (mathematically identical) will be used for existing product dimensions, and where necessary for safety. Hard conversion (rounded) will be used where safety is not an issue such as cable shall be fastened every 1.4m (4 1/2ft) and where it would not have any effect on existing products. It is not the intent of the Task Group to make any changes to the Code that would preclude the use of any existing product or require any redesign of existing products or require any new products! The Task Group will not require conversion of any industry unless the manufacturers support the action.
  • It is not the intention of the Task Group to require any change in marking requirements; it would be up to the manufacturers to select the product markings to be used.
The Sections on motors and generators would have soft conversion (mathematically identical) SI units added for such things as box opening, and clearance dimensions, spacings, volume, etc. Non-critical dimensions would be hard converted (rounded), e.g., Section 420-132(3) would be changed from "By elevation 8 ft. (2.44 m) or more above the floor." to "By elevation 2.5 m (8 ft.) or more above the floor."
  • Wire and cable will continue to use the trade designators of AWG and kcmil; there will not be any SI units for conductor size in the body of the Code. We have proposed including a column in Chapter 9, Table 8 to list the equivalent conductor area expressed in mm2. Insulation thicknesses and jacket thicknesses will be shown in SI units first (soft converted) followed by the inch-pound units in parenthesis in text, and in tables a column will be added for the SI units.
  • Raceways will be expressed in metric trade size (numerical designator) and trade size (inch-pound designator); there will not be any units attached to either trade size.
  • Box dimensions and metal thicknesses will be soft converted.
  • Trade sizes will not be changed. A 2" x 4" stud will be referred to as a 2 x 4 stud.