Cummins/Onan NTA855 Generator Set

⚠ Electrostatic discharge will damage circuit boards. Always wear a grounding wrist strap when working inside control box.

1. Press the button next to ADJUST in the Main Menu; the VOLTAGE submenu appears.
2. Press the button next to >> to move through VOLTAGE and FREQUENCY to the START DELAY submenu.
3. Use the buttons next to the up and down symbols to set the start delay.
4. Press >> to move to the STOP DELAY submenu and set the stop delay.
5. Press >> to move to the IDLE SPEED submenu and set idle speed (only in idle mode).
6. Press >> to move to SAVE/EXIT; select SAVE then EXIT to return to Main menu.

1. Press the button next to the arrow symbol in the display until the + and - symbols are displayed.
2. If necessary, press the button next to the arrows to move to the numeric character to change.
3. Press + to increase the value or select the parameter; press - to decrease the value or select the parameter.
4. Press the save symbol to save changes; changes are not saved if Home or Previous Main Menu is pressed first.

⚠ Accidental starting of the generator set during this procedure presents the hazard of severe personal injury or death. Make sure to disconnect the negative (-) battery cable(s) before beginning.

⚠ Do not bar engine over by prying on fan blade.

Tools: Dial indicator, Shims

1. Disconnect the negative (-) battery cable(s) before beginning.
2. Fasten a dial indicator to the generator shaft or cooling fan, with the sensing point on the capscrew head or drive disc flat surface at bolt circle diameter.
3. Bar the engine over clockwise as viewed from the engine flywheel; do not allow it to roll back on compression.
4. Total indicator reading (T.I.R.) is the sum of the maximum positive and negative readings as the engine completes one revolution.
5. To lower the generator, remove equal shims from under both generator mounting feet; approximate shim amount from the distance ratio.

⚠ Accidental starting during this procedure presents the hazard of severe personal injury or death.

⚠ Do not bar engine over by prying on fan blade.

Tools: dial indicator

1. Disconnect the negative (-) battery cable(s) before beginning.
2. Fasten a dial indicator to the generator shaft or cooling fan with sensing point resting on the drive disc capscrew head/flat surface at the bolt circle diameter.
3. Bar the engine over in a clockwise rotation as viewed from the engine flywheel; do not allow it to roll back on compression at the end of travel of each reading.
4. Record the total indicator reading (T.I.R.) as the sum of the maximum positive and negative dial indicator readings over one engine revolution.
5. Compare the measured T.I.R. to the maximum allowed (.001 in. per inch of radius from center of shaft to indicator axis); add or remove shims under the generator mounting feet to correct.

Tools: Dial indicator, Magnetic base or clamp

1. Check axial alignment only when an objectionable vibration is present after angular alignment.
2. Fasten dial indicator holding device to skid base, engine block, or generator shell with a magnetic base or clamp; rest sensor on generator shaft hub.
3. Bar the engine over clockwise through a couple of rotations; record indicator readings at eight equally spaced points around the shaft diameter.
4. To correct out-of-tolerance T.I.R., remove the drive disc capscrews, mark discs and flywheel, rotate 180 degrees from original location, retorque, and recheck.
5. If unchanged, rotate the discs to 30, 60 or 90 degrees from their original location.

Tools: dial indicator

1. Fasten a dial indicator holding device to the skid base, engine block, or generator shell with the sensor point resting on the generator shaft hub.
2. Bar the engine over in a clockwise rotation through a couple of rotations, recording indicator readings at eight equally spaced points around the shaft diameter to obtain axial T.I.R.
3. Reduce the measured T.I.R. runout by one half if excessive vibration remains after angular alignment.

1. Verify that the N-G Fault Indicator on the GFR is not lit; if lit, the neutral-to-ground bonding jumper circuit is open.
2. Move the control switch to the Run position.
3. Press the TEST switch on the ground fault relay.
4. Verify that the control panel warning message is displayed and the Fault Indicator (>I) on the GFR is lit.
5. Reset the control panel fault, which also resets the ground fault relay.

⚠ Medium-voltage, 601 to 15,000 volts, present special hazards of severe personal injury or death.

⚠ Windings of medium voltage generator sets must be dry before the generator is operated.

Tools: Megger, Grounding Cluster

1. Perform the Generator Set Grounding Procedure.
2. Disconnect plug J10 from voltage regulator output stage module and AC control input leads marked 4, 5, 6, 7 and 8.
3. If RTD option installed, ground all six RTD temperature leads (18 leads total).
4. Remove and separate neutral leads from generator load terminal marked N.
5. Connect megger between one stator phase and ground while grounding other two phases; conduct test.
6. Repeat for the other two phases.
7. Disconnect main rotor and voltage suppressor leads from terminals F1+ and F2- and isolate from ground.
8. Connect megger between one rotor lead and ground and conduct the test.

Tools: Jumpers

1. To convert 240 VAC to 120 VAC: remove jumpers between TB1-6 and TB1-7; connect one between TB1-5 and TB1-6 and one between TB1-7 and TB1-8.
2. Move selector switch S103 on the control PCB to the up position for 120 V.
3. If equipped with a transformer, remove jumpers between H2 and H3; connect one between H1 and H3 and one between H2 and H4.
4. To convert 120 VAC to 240 VAC: remove jumpers between TB1-5/TB1-6 and TB1-7/TB1-8; connect two jumpers between TB1-6 and TB1-7.
5. Move selector switch S103 on the control PCB to the down position for 240 VAC.
6. Attach a tag to the control box indicating the supply voltage.
7. Terminals TB1-8 and TB1-5 are available for a 120 or 240 VAC electric fuel shutoff valve rated not more than 0.5 amps.

⚠ Diesel fuel is highly combustible. Installation and service must be performed by trained and experienced persons in accordance with applicable codes.

1. Remove the two jumpers between terminals TB1-6 and TB1-7; connect one between TB1-5 and TB1-6 and the other between TB1-7 and TB1-8.
2. Move selector switch S103 on the control PCB to the up position for 120V.
3. If equipped with a transformer, remove jumpers between H2 and H3; connect one between H1 and H3 and the other between H2 and H4.
4. Attach a tag to the control box indicating the supply voltage.

⚠ Remove shipping screws (two) prior to genset operation. Genset operation with shipping screws in place will damage control components.

Tools: Leveling bolt, Lock nut, Shims or grout

1. Place the vibration isolators on the genset support structure; shim or grout so all isolator bases are within 0.25 inch (6 mm) elevation.
2. Loosen the side snubber lock nuts so the top plate is free to move; align top plate with base and springs.
3. Place the genset onto the isolators, aligning the skid's mounting with the threaded isolator hole.
4. Adjust leveling bolts until the set is level with a nominal clearance of 0.25 inch (6 mm) or greater between top plate and base.
5. Lock the leveling bolt in place with the lock nut; snubber nuts may remain loose for better isolation.
6. Model DFCE only: remove the two controller cabinet shipping screws before genset operation.

⚠ Remove shipping screws (two) prior to genset operation. Genset operation with shipping screws in place will damage control components.

Tools: Leveling bolt, Lock nut

1. Place vibration isolators on genset support structure; shim or grout bases within 0.25 inch (6 mm) elevation of each other on flat, level surface.
2. Loosen side snubber lock nuts so top plate is free to move vertically and horizontally.
3. Place genset onto isolators, aligning skid mounting with threaded isolator hole.
4. Adjust isolators using leveling bolt so set is level; nominal clearance of 0.25 inch (6 mm) or greater desired.
5. Adjust leveling bolts until set is level and sufficient clearance remains; lock leveling bolt with lock nut.
6. Snubber nuts may remain loose for better isolation.
7. Model DFCE only: remove the two controller cabinet shipping screws before operation.