NEMA PRP 4-2009 Expansion Fittings for PVC Rigid Nonmetallic Conduit.pdf
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1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA PRP 4-2009 (R2016)Expansion Fittings for PVC Rigid Nonmetallic ConduitNEMA PRP 4-2009 (R2016) Page 1 A NEMA Polymer Raceway Products Document PRP 4-2009 (R2016) Expansion Fittings for PVC Rigid Nonmetallic Conduit Published
2、by National Electrical Manufacturers Association 1300 North 17thStreet, Suite 900 Rosslyn, Virginia 22209 www.nema.org 2016 National Electrical Manufacturers Association. All rights, including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention f
3、or the Protection of Literary and Artistic Works, and the International and Pan American copyright conventions. NEMA PRP 4-2009 (R2016) Page 2 2016 National Electrical Manufacturers Association NOTICE AND DISCLAIMER The information in this publication was considered technically sound by the consensu
4、s of persons engaged in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. NEMA standards and guideline publications, of which the docum
5、ent contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in the topic covered by this publication. While NEMA administers the process and establishes rule
6、s to promote fairness in the development 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 contained in its standards and guideline publications. NEMA disclaims liabil
7、ity for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, exp
8、ressed 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 particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufactu
9、rer or sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or enti
10、ty to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this pu
11、blication may be available from other sources, which the user may wish to consult for additional 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 this document. NEMA does not certify, test, or inspect
12、products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safety-related information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. NEMA PRP
13、 4-2009 (R2016) Page 1 2016 National Electrical Manufacturers Association Expansion Fittings for PVC Rigid Nonmetallic Conduit All construction materials expand and contract with fluctuations in temperature. These temperature changes affect Polyvinyl Chloride (PVC) more than traditional materials su
14、ch as aluminum and steel. For example, the coefficient of thermal expansion for PVC (3.38 x 10-5in./in./F) is almost three times that of aluminum and six times that of steel. Thermal expansion and contraction have a significant effect on long straight runs of conduit. For this application, expansion
15、 fittings are used to accommodate changes in length. This prevents potentially harmful thermal stresses in the conduit itself or in any supporting structures. Expansion Fittings Required Section 352.44 of the National Electrical Code(NEC) requires that expansion fittings be installed for PVC rigid n
16、onmetallic conduit to compensate for thermal expansion and contraction where the length change is anticipated to be 6 mm (1/4 inch) or greater, in accordance with Table 352.44 of the NEC, in a straight run between securely mounted items. Securely mounted items are boxes, cabinets, elbows, or other c
17、onduit terminations. When Are Expansion Fittings Used? The importance of knowing when to use an expansion fitting is as important as knowing how to use an expansion fitting. Expansion fittings are used in aboveground installations where temperature changes are anticipated to exceed 25F (14C). Rigid
18、PVC conduit has a coefficient of expansion of 3.38 x 105in./in./F. A 10 foot length will change in length about 3/8” with a change in temperature of 100F. This equates to more than 4 inches over a 100 foot run. Changes in conduit temperature outdoors can exceed 140F, considering the heat of summer a
19、nd cold of winter. This means a 100 foot run of conduit could change approximately 6 inches in length between summer and winter. If not compensated for with expansion fittings, this change in length can cause unsightly conduit bowing, distorted boxes, or broken couplings or fittings. The anticipated
20、 expansion and contraction for various lengths of runs and temperature changes are given in Table 352.44 of the NEC (See table below.) BarrelPistonMuzzleNEMA PRP 4-2009 (R2016) Page 2 2016 National Electrical Manufacturers Association Expansion Characteristics of PVC Rigid Nonmetallic Conduit Coeffi
21、cient of Thermal Expansion = 3.38 x 10-5in./in./F Temperature Change Degrees F Length Change in Inches per 100 ft of PVC Conduit Temperature Change in Degrees F Length Change in Inches per 100 ft of PVC Conduit Temperature Change in Degrees F Length Change in Inches per 100 ft of PVC Conduit Tempera
22、ture Change in Degrees F Length Change in Inches per 100 ft of PVC Conduit 5 0.2 55 2.2 105 4.2 155 6.3 10 0.4 60 2.4 110 4.5 160 6.5 15 0.6 65 2.6 115 4.7 165 6.7 20 0.8 70 2.8 120 4.9 170 6.9 25 1.0 75 3.0 125 5.1 175 7.1 30 1.2 80 3.2 130 5.3 180 7.3 35 1.4 85 3.4 135 5.5 185 7.5 40 1.6 90 3.6 14
23、0 5.7 190 7.7 45 1.8 95 3.8 145 5.9 195 7.9 50 2.0 100 4.1 150 6.1 200 8.1 For Conduit Installed Outdoors, the maximum and minimum air temperature expected can be used to calculate the range of expansion and contraction. Conduit installed outdoors in direct sunlight will be considerably hotter than
24、air temperature during the day because of the absorption of the suns heat. Expansion fittings should be installed to allow for the anticipated temperature change. For direct sunlight exposure, add 30F to ambient air temperature change. Where Installed Inside Buildings, the conduit temperature is the
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