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Home›Engines›Cummins/Onan NT855

Cummins/Onan NT855 Engine Engine

The Cummins/Onan NT855 is a 14 L 6-cylinder turbo charged engine rated at 1800 rpm, producing up to 354 kW. It powers generator sets from Cummins/Onan, including the C350 D5, C350 D6, C400 D5 and C400 D6. It holds 40 L (10.6 gal) of oil and 51 L (13.5 gal) of coolant.

Also known as: Cummins NT855, NT 855

Part of the Cummins/Onan NT855 engine family — 5 variants share parts & fitment.

14.0 L
Displacement
6
Cylinders
1800 rpm
Rated speed
354 kW
Gross power

Engine specifications

Oil capacity40.0 L
Coolant capacity51.0 L
Displacement14.0 L
Cylinders6
AspirationTurbo Charged
Rated speed1800 rpm
Gross power354 kW

Generator sets powered by this engine

10
Cummins/Onan C350 D5Cummins/Onan C350 D6Cummins/Onan C400 D5Cummins/Onan C400 D6Cummins/Onan C440 D5Cummins/Onan DFCummins/Onan DFBFCummins/Onan DFCBCummins/Onan DFCCCummins/Onan NT 855

Common problems

15
  • UNDER FREQUENCY 313
    Fix: Shutdown
  • SHORT CIRCUIT 322
    Fix: Shutdown
  • Over Current 1471
  • LOW OIL PRESSURE 200
    Fix: Shutdown
  • Low Coolant Level 197
  • LOW AC VOLTAGE 303
    Fix: Shutdown
  • High Coolant Temp 211
    Fix: Indicates engine has begun to overheat and coolant temperature has risen to an unacceptable level: (215° F − standby / 207° F − primary).
  • HIGH AC VOLTAGE 301
    Fix: Shutdown
  • No AC output voltage.
    Fix: Contact an authorized service center.
  • Weak Battery 1442
  • Warning, Shutdown, and Non-Automatic lamps are not lit. Digital display shows main menu or selected menu.
    Cause: Indicates all engine systems are normal. No corrective action required
  • Warning lamp lights. MESSAGE: WEAK BATTERY 232 - WARNING 232
    Fix: Indicates battery voltage drops below 60% of nominal for two seconds, during starting. a. Discharged or defective battery. See Warning message 230, LOW DC VOLTAGE.
  • Warning lamp lights. MESSAGE: RUPTURE BASIN 262
  • Warning lamp lights. MESSAGE: OVERLOAD 330
    Fix: Indicates that three-phase power output exceeds 105% of standby (or 115% of prime) rating. After five seconds, the Load Dump output is activated. After 60 seconds, the OVERLOAD warning is activated. Contact an authorized service center.
  • Warning lamp lights. MESSAGE: OVERCURRENT 320
    Fix: Indicates that generator output current has exceeded 110% of rated for 60 seconds. Contact an authorized service center.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan NT855.

Maintenance schedule

ItemSpecCapacityPart #Interval
Air filterair cleaner—1000 hr find
Fuel filterfuel filter—500 hr find
Oil filterengine oil filter—1000 hr find
Beltfan belt, water pump belt—1000 hr find
Coolantcooling system80.63 gallons—5000 hr
Coolant filter— find
Oilengine oil10.0 gallons—100 hr

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Parts cataloged across the Cummins/Onan NT855 family

157
Part #DescriptionCategory
140-1347Cap, Air Cleanerair_filter
140-2391Element - Air Cleaner (Standard)air_filter
155-1035Cleaner, Airair_filter
232A1817Generatorair_filter
503-0641Hose, Flexible Air Cleanerair_filter
503-0748Clamp, Hose - Air Cleanerair_filter
CS-1382cINLET AIR DAMPERair_filter
ES-1214-2FLOAT SWITCHair_filter
191-0688Alternator - Includes Regulator (Motorola #70D44039B04)alternator
191-0781191-0688 talternator
191-1981Fan, Alternatoralternator
191-1982Pulley, Alternatoralternator
191-1983-02Alternator, 24 Volt Spec B-O (Prestolite)alternator
302P412AMMETER, AC (CHECK SCALE - SELECT ACCORDING TO RATING) Scale 0-250ammeter
302P414AMMETER, AC (CHECK SCALE - SELECT ACCORDING TO RATING) Scale 0-500 (Qty. is 2 for I-Ph.)ammeter
234070Rig Assy., Brush- Incl. Brushes, & Contact Point Band, Gen. - Front Portion(Narrow)band
A9562-12 VOLT BATTERIESbattery
2110153Bell, End - Alt, to Exciterbell
191-0725Guard, Beltbelt
511-0084130-3176-02 1 191-1926-02 70D44970S02 MO 1 3RG3032 MO 1 511-0156 2 LO 3318853 CE 1 12belt
511-0092Belt, Alternatorbelt
805-35Bolt, Place - Generator Mtg. Support to End Bellbolt
1S0A713Bracket, Overspeed Switchbracket
2348115Bracket, Mtg. - Volt. Cont. Reactorbracket
234875Bracket, Gate Reactor Mtg.bracket
319-2236Bracket, Mountingbracket
2I4AMBrushbrush
505-0019Bushing, Pipe - Reducer 1/2” to 3/8”, DFBF (1/2” to 3/8”) 505-0131 DFCB, DFCC, DFCE (3/4” to 3/8”)bushing
518-0548-58Clamp, Hoseclamp
2340116Cover, Excitercover
0300-4623-08DFBF (600V)current_transformer
0300-4623-23DFBF BR (0-480V)current_transformer
FS1803sFUEL FILTERSfuel_filter
FP-KS12622ANH/NT855 In-Frame Kit w/upper gasket set & oil pan gasketgasket
FP-KS12622CNH/NT855 In-Frame Kit w/upper gasket set & oil pan gasketgasket
FP-KS12622C7NH/NT855 In-Frame Kit w/upper gasket set & oil pan gasketgasket
FP-KS12622DNH/NT855 In-Frame Kit w/upper gasket set & oil pan gasketgasket
M-4024945Edge molded rubber head gaskets setgasket
501-0087ClamD, Hosehose
502-0827Hose, Barb (1/2–14)hose
503-0189Clamp, Hosehose
503-0354Clamp, Hosehose
503-0752Hose, Upperhose
503-0756Hose, Radiator (Lower)hose
503-1634-01Hose, Rubber (3/4” ID x 4”)hose
302P465RUNNING-TIME METERS 120-240V (1PH)meter
302P466For 220/380-V, 3-Ph, 60-Cycle (Model H)meter
302P467For 277/480-V, 3-Ph, 60-Cyclemeter
302P468For 120/208-V,120/240-V, & 347/600-V 3PH. 50 Cy!. (825-Ohm, 75-Watt)meter
302P469For 220/380-V, 3Ph. 50-Cyclemeter
302P470For 277/480-V, 3-Ph, 50-Cyclo (5-P!)meter
309-0641-03Switch, Low Oil Pressure (S110)oil_filter
102-1335Plug, Oil Drainother_service
130-0843Bracket, Radiator Supportother_service
130-0846Opening for 34" Fanother_service
130-0924Clamp, Hoseother_service
130-0992Radiatorother_service
130-3588Cap, Radiatorother_service
130-4355Radiator (2 Row Core) DFBJother_service
130-4355-01Radiator (3 Row Core) DFCF, DFCGother_service
130-4369Radiator DFCHother_service
140-1349Cable, Battery Positiveother_service
140-2389140-2391 1 140-2390 1 140-2392 1 140-2393 1 140-1548 1 140-1545 1 c 503-1575 186917 Cother_service
155-2409-01Elbow, Exhaust (5" OD With Threads)other_service
191-1141Bracket, Alternator Mountingother_service
191-2121Regulator, Voltageother_service
232A1489Generator support shim, 0.598 in gauge #6, 3x3other_service
232A1490Generator support shim, 0.359 in gauge #20, 3x3other_service
301021151Box Only, controlother_service
30118301Bracket, Cont.Box Mtg. (Repl. 2-Piece Brkts)other_service
301A1914Bracket, Panel Stopother_service
301A2727Handle , Control Boxother_service
302-21360-Cycleother_service
302-234.Cycleother_service
3028448Plate, Mater Faceother_service
302P411302P412other_service
302P415Scale Reads 0-750 (I-Phase Use 2)other_service
302P421AC VOLTAGE RESISTOR METERS 600Vother_service
302P422302P423other_service
302P423AC VOLTAGE RESISTOR METERS 1000Vother_service
303-111Rheostat, Volt. Reg. - 175-Ohm, (Model H)other_service
303-32Knob, Rheosother_service
304030545, 000-Ohm, 10-W - For 480-V , 3-Ph, 3-Wire & 277/480-V, 3+ Ph.other_service
308-22Switch, Meter Selectorother_service
309-01691 Begin Spec G 25 26other_service
320823-Phase Modelsother_service
320B18Single Phase Modelsother_service
333-0639-01Heater, Coolant (4990 Watt)other_service
333-0639-02Heater, Coolant (6420 Watt)other_service
337A44Strap, Groundother_service
402-78Rubber, Mtg. - Cont. BOX to Mtg. Brkt.other_service
503-0197503-0197 Miscellaneous Engineother_service
503-1575CE 1 155-1241 190351 CE 1 155-2409 1 155-2281 203432 CE 1 155-2287-02 3036377 CE 1 oother_service
504-0011Valve, Shutoff (1/2”)other_service
504-0028Valve, Radiator Drainother_service
505-0100Nipple, Pipe - Close (1/2”)other_service
526-0219Washer, Flat (1/2)other_service
800-0048Screw, Cap - Hex Head (3/8-16 x 3/4”)other_service
850-0050Washer, Lock - Spring (3/8”)other_service
870-0212Nut, Locking (1/4-20)other_service
960-0138other_service
960-0606other_service
EXS-1046sCONDENSATION TRAPother_service
FP-855PREMNH/NT855 Premium Cylinder Kitsother_service
FP-855TTNT855 Premium 3-Ring Cylinder Kitsother_service
FP-855TTDNNT855 Premium 3-Ring Cylinder Kits Dual-NI Pistonsother_service
FP-855TTPNT855 Premium Plus 3-Ring Cylinder Kitsother_service
FP-855TTPDNNT855 Premium Plus 3-Ring Cylinder Kits Dual-NI Pistonsother_service
FP-IFK855NRNT855 Cylinder Kits w/ no piston ringsother_service
FP-IFK855PREMNH/NT855 Premium Cylinder Kitsother_service
FP-IFK855TTNT855 Premium 3-Ring Cylinder Kitsother_service
FP-IFK855TTDNNT855 Premium 3-Ring Cylinder Kits Dual-NI Pistonsother_service
FP-IFK855TTPNT855 Premium Plus 3-Ring Cylinder Kitsother_service
FP-IFK855TTPDNNT855 Premium Plus 3-Ring Cylinder Kits Dual-NI Pistonsother_service
FP-KS12621CNH/NT855 Cylinder Kit Std Head Gask Grommetsother_service
FP-KS12621C7NH/NT855 Cylinder Kit .010 Head Gask Grommetsother_service
FS1692sFUEL SOLENOID VALVE LOCATIONother_service
M-1808DC CONTROL WIRINGother_service
TB11-29Engine Monitor Boardother_service
TB11-30Engine Monitor Boardother_service
TB11-31Engine Monitor Boardother_service
234C1343-Phasephase
234C1373-Phasephase
234C140Single Phasephase
234C141Single Phasephase
305P233Rectifier Only, Power (Field) - Lower two - Negative (Begin Spec 'C' included in Rectifier & Reactor Assembly #305B227)rectifier
305P234Rectifier Assy., Power (Field) (Incl. in Rect. #305P218)rectifier
305P240Rectifier, Volt. Cont.Reactor (Incl.in Rect. & Resistor A: 305P218)rectifier
3ISA78Rectifier, Voltage Controlrectifier
307-2621-02Relay, Start Solenoid (K4)relay
304412515,000-Ohm, 25-W - For 220/380-V, 3-Phase, 4-Wireresistor
304PA76Resistor, Volt. Cont.Reactor (Incl.in Rect.& Resistor A: 305P218)resistor
3058227Resistor Assy., Rect, & Incl. (Incl.in Rect. & Resistor A: 305P218)resistor
204493Ring, Collectorring
800-0092Screw, Cap - Hex Head (1/2-13 x 1.5)screw
DM-3010461Crankshaft Rear Seal - NT855, NTC855seal
193-0108Sender, Oil Pressuresensor
193-0244Sender, Oil Pressure (E1)sensor
193-0432Sender, Oil Temperature (S2 Engine Block, E4 Oil Pan)sensor
193-0447-01Sender, Water Temperature (E2)sensor
193-0448Sender, Oil Pressure (Includes Parts Marked *)sensor
309-0178Sender, Water Temperaturesensor
309-0269Air Cleaner (Includes Element) - Standardsensor
309-0576Switch, Thermostat - High Engine Coolant Temperature (S2)sensor
309-0641-07Switch, Oil Pressure (Closes at 20 lbs. Descending)sensor
960-0504PCC Control Service Manualservice_manual
960-0507Detector Control Service Manualservice_manual
191-0852Starter (24 Volt)starter
191-1858Starter (24VDC)starter
3320645Strip, Marker - Volt. Con. Reactor (9305P218)strip
5208190Stud, Fixed Resistor Mtg.stud
23201396Support, Gen. Mtg.support
1S0A717Switch Assy., Overspeedswitch
B-342-3sPRIMING TURBOCHARGER OIL SUPPLY INLET LINE. DISCONNECT AT THIS POINT TO PRIMEturbocharger
304A15S Washer, Fixed Resistor Cent. to Alternator End Bellwasher
508-0292Washer, Sealing - Copperwasher
526-0029*Washer, Flat (1/2")washer

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Aftermarket parts that fit this engine

2
0327-1507 PartsGeek FridayParts $499.99 FP-XP-0041835 PartsGeek

Parts listed by aftermarket suppliers as fitting this engine — leads compiled from supplier catalogs; verify the exact part for your serial number.

Common questions

What is the oil capacity of the Cummins/Onan NT855?

The Cummins/Onan NT855 engine has an oil capacity of 40.0 liters.

What is the displacement of the Cummins/Onan NT855?

The Cummins/Onan NT855 has a displacement of 14.0 liters with 6 cylinders.

Which generators use the Cummins/Onan NT855 engine?

The Cummins/Onan NT855 powers 10 generator set(s), including Cummins/Onan C350 D5, Cummins/Onan C350 D6, Cummins/Onan C400 D5, Cummins/Onan C400 D6, Cummins/Onan C440 D5.

How often should you change the oil in the Cummins/Onan NT855?

The Cummins/Onan NT855 oil change interval is every 100 hours.

What is a common problem with the Cummins/Onan NT855 engine?

A commonly reported issue on generators using the Cummins/Onan NT855 is: UNDER FREQUENCY. Fix: Shutdown.