![]() ![]() Find the required wire size from the value in the proper column in the proper table. Divide the ampacity of the wire determined in step 1 by each of the derating factors in turn to get a final ampacity requirement ģ. Figure a minimum wire size for a maximum Vd (I use 3% for feeders) at full load amps Ģ. You don't exactly "derate" for voltage drop. Don't forget that the conductor jacket temperature rating cannot exceed the temperature rating of the conduit (usually 90 deg C, so MV-105 is out for PVC). If medium voltage, you also need to derate for induced shield currents. If medium voltage, go to B.310-77 or somewhere close by. Use ambient derating factors at the bottom of the table, also. You did not indicate the system voltage, ampacity, and number of circuits, but assuming you are at 480 VAC, then table B.310-7 includes different colums for derateing based on the number of circuits. The code book says that is good for 90% of USA. Once all the runs of conduit are in place and properly connected, the crew fills the trench with cement and the ends of the pipe are directed into and terminate in approved electrical devices or boxes.I would use rho = 90 as a starting point. Once more, CANTEX PVC Pipe Solvent Cement needs to be applied with a dauber in between each run.Ĥ. Once again, the entire installation process needs to be repeated for every 10 or 20 feet, depending upon the length of the conduit.ģ. See the CANTEX Full Product Line Catalog for determining the NEC 70 spacer requirements for the necessary trade size of the spacers and the required separation space. The rows of CANTEX PVC Intermediate Spacers are connected for every row of pipe. The amount of spacers coordinates with how many rows of conduit are being installed. Once the trench is completed, CANTEX PVC Base Spacers must be placed in rows in the trench. The process begins with the crew digging the trench.Ģ. Once again, the process for encasing Direct Burial and Encased Burial PVC Utility Duct in cement is basically the same as the cement encasement process for Schedule 40 and 80 PVC Pipe. Once all the runs of PVC DB Conduit are in place and properly connected, the crew fills the trench with dirt.ĭB Direct Burial & EB Encased Burial Cement Installation This process is repeated every 10 to 20 feet, depending upon the length of the conduit.ĥ. The pipe is twisted slightly to secure it. Once the pipe is smooth, the correct type of CANTEX PVC Solvent Cement gets applied to the inside of the belled end and the outside of the spigot or “straight” end of the conduit with a dauber.Ĥ. If the pipe has been cut, a reamer tool must be used to remove burrs or debris before cementing. In between each run of pipe, the belled end of the conduit gets cemented to the straight end. A crew begins by digging a trench for the conduit.Ģ. ![]() Consequently, the ends of the DB PVC Conduit runs are directed into and terminate in approved electrical devices or boxes. For example, smoother select fill dirt would be used as back-fill and there are no above-ground applications for Direct Burial PVC Conduit. DB Direct Burial PVC Utility Duct InstallationĪlthough the direct burial installation for DB PVC Utility Duct is very much the same as it is for Schedule 40 and Schedule 80 PVC Pipe, there are some differences in back-fill requirements and performance capabilities. ![]()
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