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Cummins/Onan ATUC A 800 - 4X / 111 — C output voltage

For the Cummins/Onan ATUC A 800 - 4X / 111.

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Procedure

  1. 29.
  2. 31.
  3. replace it with one of the other undervoltage sensors. Then perform the. calibration procedures in this position. After calibration is complete, remove the dis- connect plug. Disconnect the Multi-Tester or variac and voltmeter. Reconnect the wire lead removed in Step 11 and install the plastic cover over the terminals. Close the control accessory panel and reconnect the disconnect plug. Make the sensor settings. See “Undervoltage Sensor Settings” (near end of section). Overvolitage Sensor
  4. 2.
  5. Open the cabinet door of the automatic transfer switch. Move the operation selector switch on engine control to “STOP.” Turn the “% DROP-OUT DIFFERENTIAL.” kuohs to minimum and the “PICK-UP VOLTAGE” knobs to the clockwise limit (maximum). On the sensor to be calibrated, turn “PICK-UP VOLTAGE” knob very slowly counterclockwise until you hear relay K6 close. This reading times the multiplying factor should equal the line voltage. Check line voltage with a voltmeter, divide by the factor to see
  6. 12.
  7. 14.
  8. 16.
  9. 18.
  10. 20. lead from the stepdown transformer’s right side terminal of the terminal strip for the respective sensor. For example, if the nominal voltage is 208 volts, remove the wire lead from T2-3 for sensor
  11. Do not remove the common (com) lead. See Figure 26. If available, connect an Onan Multi-Tester to the transformer terminals of the terminal strip and the wire lead removed using the instructions in the Multi-Tester. If using a variac, connect its com- mon output lead to transformer T2-1 (com) and its other output lead to terminal 2 (120-volt connec- tion). See Figure 27. Connect a voltmeter to the output leads of the variac. Connect the variac input to a 120-volt AC source. Be sure the common
  12. If it does, proceed to Step 19. Setting Too Low: (a) Turn the “% DROP-OUT DIFFERENTIAL” knob counterclockwise to minimum. (b) Turn the “PICK-UP VOLTAGE” knob to the desired setting. (c) Insert a small screwdriver through the “CALIBRATE” hole and turn counterclockwise very slowly until you hear relay K6 pick up. Setting Too High: (a) Turn the “PICK-UP VOLTAGE” knob to its clockwise limit. (b) Inserta small screwdriver through the “CALIBRATE” hole and turn to its clockwise limit. (c) Turn the “P
  13. 22.
  14. 24.
  15. 26.
  16. 28.
  17. 30. TIAL.” With the knob: set at 5 percent, relay K6 should drop out at approximately 95 percent of 132 volts = 125 to 126 volts. If not, use a small screwdriver to loosen the knob and reposition so it indicates 5 percent with drop-out voltage of 125 to 126 volts. Set the “PICK-UP VOLTAGE” and “% DROP- OUT DIFFERENTIAL” knobs at desired settings. Increase the voltage with the Multi-Tester or variac until you hear relay K6 pick up. Decrease the voltage with the Multi-Tester or variac until yo
  18. 3.
  19. Turn the “PICK-UP VOLTAGE” knob to the desired pick-up voltage (voltage at which load is transferred from g enerator set to commercial power). Unless you have special equipment which can be damaged by slight voltage changes; a setting which gives pickup at 90 percent of the © nominal voltage is usually satisfactory. Forexam- - ple, 90 percent of 120 volts (for a 120-volt system) gives 108 volts for the knob setting. The drop-out differential is determined by the pick-up setting. Turn the “%
  20. Turn the “PICK-UP VOLTAGE” knob to the desired pick-up voltage (voltage at which load is transferred from commercial power to the generator set). Unless you have special equip- ment which can be damaged by slight voltage changes, a setting (13 percent) which gives pick- up at 113 percent of the nominal voltage is usually satisfactory. Forexample, 113 percent of 120 volts (fora 120-volt system) gives 135 volts for the knob setting. The drop-out differential is determined by the pick-up setting.
  21. 3. Turn the “% DROP-OUT DIFFERENTIAL” knob to the desired deviation below the pick-up voltage. This setting is the voltage at which the load is transferred from the generator set to commercial power. A setting of 5 percent is often satisfactory. For example, 5 percent of 135 volts (pick-up voltage from Step 1) is approximately 7 volts. The drop-out voltage is then pick-up voltage minus the differential voltage, 135 - 7 = 128 volts. After settings are finished, move the operation selector switc
  22. Close cabinet door. TROUBLESHOOTING POWER OUTAGE OCCURS, BUT GENERATOR SET DOES NOT START
  23. Check for overcrank condition.
  24. Check position of operation selector switch. Should be at “RMT.”
  25. Check generator set. Start with start-stop switch on generator set. If it does not crank, check starting batteries. If it cranks but does not start, check fuel supply. GENERATOR SET STARTS DURING NORMAL SERVICE Check position of operation selector switch on engine control. Should be at “RMT.” Check position of selector switch in cabinet. Should be at “NORMAL.” Check if exerciser clock is turned to exercise period. Check to see if contro! panel disconnect plug is inserted into receptacle. Ch
  26. Check position of operation selector switch. Should be at “RMT.”
  27. Check exerciser clock to see if it is set correctly and running.
  28. Check generator set. Start with start-stop switch on generator set. If it does not crank, check starting batteries. If it cranks but does not start, check fuel supply. GENERATOR SET STARTS BUT DOES NOT ASSUME LOAD
  29. Check position of motor disconnect switch on the transfer switch. Should be at “ON.”
  30. Check output voltage of the generator set.
  31. Check generator-side undervoltage sensor (if equipped) pick-up voltage setting. Settingin | most cases should be at 100 volts. NO TRANSFER OF LOAD TO COMMERCIAL POWER FROM GENERATOR SET |
  32. Check position of motor disconnect switch on the transfer switch. Should be at “ON”
  33. Check disconnect plug in control accessory panel. Must be connected into receptacle.
  34. Check retransfer time delay (if used) to see if time delay is still operating. See OPERATION section.
  35. If automatic transfer switch has battery charging feature, check battery charging fuse. Replace if necessary with Buss KTQ1 fuse or equivalent.
  36. Manually initiate retransfer by operating retransfer selector switch and push to retransfer switch (if equipped).
  37. Stop generator set with start-stop switch. When generator set stops, the transfer switch will transfer the load to the normal power line if voltage is normal. GENERATOR SET CONTINUES TO RUN AFTER RETRANSFER OF LOAD TO COMMERCIAL POWER Start-Stop time delay may be defective. Stop generator set with Start-stop switch. -_ ae 31 BATTERY CHARGER FAILS TO CHARGE Check battery charger fuse F1 in control accessory panel (if equipped with charger). Replace if necessary with Buss KTQ1 fuse or equiva

Source: manual:962-0101 Onan AT 800 to 1750A Transfer Switch Operators Manual (11-1981).pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.