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NEMA Standards Publication TCB 2-2017Guidelines for the Selection and Installation of Underground Nonmetallic RacewaysPublished byNational Electrical Manufacturers Association1300 North 17th Street, Suite 900Rosslyn, Virginia 22209www.nema.org 2017 National Electrical Manufacturers Association. All rights, including translation into otherlanguages, reserved under the Universal Copyright Convention, the Berne Convention for the Protectionof Literary and Artistic Works, and the International and Pan American Copyright Conventions.
NOTICE AND DISCLAIMERThe information in this publication was considered technically sound by the consensus of personsengaged in the development and approval of the document at the time it was developed. Consensusdoes not necessarily mean that there is unanimous agreement among every person participating in thedevelopment of this document.NEMA standards and guideline publications, of which the document contained herein is one, aredeveloped through a voluntary consensus standards development process. This process brings togethervolunteers and/or seeks out the views of persons who have an interest in the topic covered by thispublication. While NEMA administers the process and establishes rules to promote fairness in thedevelopment of consensus, it does not write the document and it does not independently test, evaluate,or verify the accuracy or completeness of any information or the soundness of any judgments containedin its standards and guideline publications.NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever,whether special, indirect, consequential, or compensatory, directly or indirectly resulting from thepublication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty orwarranty, expressed or implied, as to the accuracy or completeness of any information published herein,and disclaims and makes no warranty that the information in this document will fulfill any of your particularpurposes or needs. NEMA does not undertake to guarantee the performance of any individualmanufacturer or seller’s products or services by virtue of this standard or guide.In publishing and making this document available, NEMA is not undertaking to render professional orother services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owedby any person or entity to someone else. Anyone using this document should rely on his or her ownindependent judgment or, as appropriate, seek the advice of a competent professional in determining theexercise of reasonable care in any given circumstances. Information and other standards on the topiccovered by this publication may be available from other sources, which the user may wish to consult foradditional views or information not covered by this publication.NEMA has no power, nor does it undertake to police or enforce compliance with the contents of thisdocument. NEMA does not certify, test, or inspect products, designs, or installations for safety or healthpurposes. Any certification or other statement of compliance with any health or safety–related informationin this document shall not be attributable to NEMA and is solely the responsibility of the certifier or makerof the statement. 2017 National Electrical Manufacturers Association
NEMA TCB 2-2017Page iForewordThese guidelines are intended to assist in obtaining the most appropriate and satisfactory installation ofrigid nonmetallic conduit (RNC) or raceway systems.These guidelines are in no way intended to assume or replace any responsibilities of engineers, customerrepresentatives, owners, or other persons in establishing engineering design practices and proceduresbest suited to individual job conditions.Typical Installation Using SpacersNEMA TCB 2 was approved by the NEMA Polymer Raceway Products Section. Approval does notnecessarily imply that all members of the Section voted for its approval. At the time of approval, theSection consisted of the following members:Anamet Electrical, Inc., Mattoon, IL, www.anacondasealtite.comAFC Cable Systems, a part of Atkore International, New Bedford, MA, www.afcweb.comAllied Tube and Conduit, a part of Atkore International, Harvey, IL, www.alliedtube.comChampion Fiberglass, Inc., Spring, TX, www.championfiberglass.comElectri-Flex Company, Roselle, IL, www.electriflex.comFRE Composites, St. Andre-d'Argenteuil, PQ, Canada, www.frecomposites.comHubbell Incorporated, Shelton, CT, www.hubbell.comIPEX Group, Mississauga, ON, Canada, www.ipexinc.comLegrand North America, West Hartford, CT, www.legrand.usPanduit Corporation, Tinley Park, IL, www.panduit.comRoyal Building Products, Shelby Township, MI, www.royalbuildingproducts.comSouthern Pipe, Inc., New London, NC, www.southern-pipe.comSouthwire Corporation, Carrollton, GA, www.southwire.comThomas & Betts, a member of the ABB Group, Memphis, TN, www.tnb.com,Underground Devices, Inc., Northbrook, IL, www.udevices.comUnited Fiberglass of America, Springfield, OH, www.unitedfiberglass.comThe NEMA Polymer Raceway Products Section will periodically review this standard and revise it asnecessary.Proposed or recommended revisions can be submitted to:Senior Technical Director, OperationsNational Electrical Manufacturers Association1300 North 17th Street, Suite 900Rosslyn, Virginia 22209
NEMA TCB 2-2017Page iiCONTENTSScope . 1Nomenclature . 1Reference Publications . 1Selection of Conduit and Duct . 24.1Types of Raceway. 24.1.1Raceway Designed for Encased Burial (EB) in Concrete . 24.1.2Raceway Designed for Direct Burial (DB) . 24.2Pipe Stiffness . 35Handling and Storage of Conduit and Duct. 35.1Handling . 35.2Storage . 45.2.1Framed Units . 45.2.2Coils and Reels . 45.2.3Bulk Storage . 55.2.4Elbows and Sweeps . 55.2.5Fittings, Spacers, and Accessories . 55.2.6Cleaners, Primers, Cements, and Adhesives . 55.2.7Inventories . 55.3Handling on the Jobsite. 55.3.1Conduit and Duct . 55.3.2Coils and Reels . 55.3.3Solvent Products . 56Installation of Conduit and Duct . 66.1Proper Installation . 66.2Trench Excavation . 66.2.4Trench Wall . 76.2.5Trench Bottom . 76.3Conduit and Duct Separation . 76.3.1Raceway Supports . 76.3.2Power Duct Banks . 86.3.3Communication Duct Banks . 96.3.4Combined Power and Communication Duct Banks . 96.3.5Spacer Specifications . 96.4Joining of Raceway . 96.5Encased Burial (EB) of Rigid Nonmetallic Conduit (RNC) . 9. 9Example of Concrete Encasement . 96.5.1Conduit and Duct Laying . 106.5.2Spacers . 106.5.3Sequence of Laying . 106.5.4Closure of a Run between Manholes . 106.5.5Temperature . 106.5.6Anchoring . 116.5.7Concrete Pour . 116.5.8Backfilling . 116.6Direct Burial (DB) of Rigid Nonmetallic Conduit (RNC) . 126.6.1Conduit and Duct Laying . 126.6.2Temperature . 126.6.3Elbows or Bends for Grade Changes. 126.6.4Raceway Embedment and Final Backfill . 126.6.5Compaction . 136.7Expansion Fittings . 136.8Field Bending . 146.9Short-Radius Elbows . 146.10 Conduit and Duct Repairs . 146.10.1 Conductors and Cabling . 141234 2017 National Electrical Manufacturers Association
NEMA TCB 2-2017Page iii6.10.2 PVC Raceway and RTRC (Cables de-energized and removed) . 14. 186.10.4 High Density Polyethylene (HDPE) . 186.11 Connections to Conduit Systems of Other Materials . 186.12 Conduit Rodding (Fishing) . 186.13 Mandrelling .
NEMA TC 2 . Electrical Polyvinyl Chloride (PVC) Conduit. NEMA TC 6 & 8 . Polyvinyl Chloride (PVC) Plastic Utilities Duct for Underground Installations . NEMA TC 7 . Smooth-Wall Coilable Electrical Polyethylene Conduit. NEMA TC 14.BG, TC 14.AG, TC 14.XW . Reinforced Thermosetting Resin Conduit (RTRC) and Fittings . NEMA TCB 4 . Guidelines for the Selection and Installation of Smooth-Wall .
