IB-80000A Non Segregated Phase Bus Duct - Powell Industries, Inc.

Non Segregated Phase Bus DuctIB-80000AA power supply of the proper voltage and capacitymust be connected to the space heater circuits.Refer to the drawings supplied with the bus duct todetermine the proper power supply and connectionpoint. If the bus duct is connected to Powellswitchgear, the space heater supply may be providedin the switchgear.The final installation step is to replace the bus ductcovers and tighten all hardware used to secure thesecovers.VI.CHECKS BEFORE ENERGIZINGBefore energizing the bus duct for the first time, thereare several checks that should be made. To performthese checks, the bus duct conductors must beisolated from the remainder of the electrical system.If disconnect switches or circuit breakers are availableto isolate the bus duct run, open these devices. Ifthere are no disconnecting devices available, unboltthe last connecting link at the end of the bus ductrun.First, check the phasing of the bus duct run fromend to end to insure that the connected apparatusis properly phased. This phasing check can be madewith a bell set, a buzzer, or an ohmmeter. Checkeach phase for continuity, and to be sure it is notconnected to any other phase or to ground.The other major check to be made before energizingis an insulation resistance test. Use an insulationresistance tester (“Megger”) rated at least 500V.Check each phase by connecting the other twophases to the grounded enclosure and measuringbetween the phase under test and the enclosure.Because insulation resistance is a function of thelength of a bus duct, the number of bus supports,the number of conductors per phase, and otherfactors, there is not a fixed value of insulationresistance which is always acceptable. For a new, dryinstallation, any resistance less than one megohm perkV of rated voltage should be questioned. Recordthe values obtained from this test for future use inthe maintenance of the bus duct. See Section VIII,“MAINTENANCE”, for further information.If it is desired to perform a power frequencywithstand test (ac “hipot”) on the bus ductconductors, the test voltage should not exceed 75%of the 60Hz hipot voltage given in Table I for the classof bus duct being tested. DC hipot testing is notrecommended for bus ducts, but if it is required, thetest voltage should not exceed 75% of the dc hipotvoltage given in Table I for the class of bus duct beingtested.If the bus duct is equipped with heaters, the heatersand their wiring should be checked for insulationresistance to ground. Disconnect the power sourcefrom the heater circuit and remove any deliberategrounds on the heater wiring. Connect all conductorsof the heater circuit together and use an insulationresistance tester rated 500V to test between theconductors and ground.Reconnect the heater circuit and energize it fromthe proper power source. Check that all heatersare operating. This may be done by calculating theexpected heater current from the heater circuitsshown on the bus duct drawings and checking thecurrent with a hook-on ammeter or other appropriatetest instrument. Heater operation may also bechecked by feeling near the heater location to notewhether or not it is producing heat.CAUTIONDO NOT TOUCH THE HEATER ELEMENTS.SEVERE BURNS MAY RESULT FROM DIRECTCONTACT WITH AN ENERGIZED HEATER.Once these checks have been made successfully,reconnect and reinsulate any connections that weredisconnected for the checks, and replace any coversremoved. The bus duct should now be ready forenergizing.VII.ENERGIZING THE BUS DUCTThere should be no load on the bus duct when it isenergized. Since bus duct typically extends betweentwo pieces of electrical apparatus, care should betaken to see that all devices fed from the bus duct areswitched to the “OFF” position before energizing thebus duct.Powered by Safety ® 11