January 2018 Vol. 73 No. 1


NEMA Publishes New Guideline, Standard

The National Electrical Manufacturers Association (NEMA) has published its new Guideline for the Selection and Installation of Smooth-wall Coilable High-Density Polyethylene (HDPE) Conduit, NEMA TCB 4-2016.  Developed and written with the participation of the Plastics Pipe Institute, Inc. (PPI), it provides recommendations for the selection, handling and installation of underground HDPE conduit or raceway for power, lighting, signaling and communications applications.  PPI is the major North American trade association representing all segments of the plastic pipe industry.

“This new guideline is very helpful for contractors, system designers and others because it provides relevant information needed for the correct installation,” said Lance MacNevin, P.E., director of engineering for PPI’s Power & Communications Division.  “It applies to both direct burial and encased burial installations, and covers topics such as handling, joining methods, separation and mandreling.”

NEMA also released an update to its Standards Publication TC 7-2016, Smooth-Wall Coilable Electrical Polyethylene Conduit, which supersedes NEMA Publication TC 7-2005.

The standard covers several wall types of HDPE conduit used to provide a protective raceway for electrical and communication cables buried underground or encased in concrete. Additionally, the standard addresses the factory installation of electrical cable or pull media commonly used to assist in the installation of cables.  End-use applications include power distribution, site lighting, signal and control, and Supervisory Control and Data Acquisition (SCADA).

“This is another key document that provides further benchmarks for the growing use of HDPE conduit,” said MacNevin. “This is because HDPE conduit properties, especially its flexibility, make it ideal for horizontal directional drilling installation as well as plowing or open trenching.”

The updated NEMA TC 7-2016 includes diameters ranging from one-half to 8 inches, along with five electrical polyethylene conduit (EPEC) wall types including EPEC 17 (SDR 17), EPEC 13.5 (SDR 13.5), EPEC 40 (Schedule 40) and EPEC 80 (Schedule 80) and EPEC 11 (SDR 11) and adds the definition for EPEC-15.5 HDPE and new dimensional and pipe stiffness requirements for this type of conduit.

HDPE conduit is used to house and protect electrical power and telecommunications cables.  Benefits, according to PPI, include availability in long lengths without joints, high strength, flexibility, proven reliability and installation toughness.  HDPE conduit, including Cable in Conduit (CIC), is widely used in trenching, horizontal directional drilling (HDD) and plowing installations.

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