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Cummins/Onan RS 25 Generator Set

The Cummins/Onan RS 25 is a 25 kW (25 kVA) Natural Gas / Propane standby generator set powered by a Cummins/Onan QSJ2.4 engine. It is available at 120/240 V, single-phase, 60 Hz and rated 104.2 A. It holds 12.8 L (3.4 gal) of coolant, with a maximum ambient rating of 40 °C. Starting uses 1 battery rated 550 CCA at 12 V. The set measures 1829×864×1156 mm (72.0×34.0×45.5 in), weighs about 503 kg (1109 lb) and produces 64 dBA at 7 m.

25 kW
Standby
2.4 L
Displacement
2
Document types

How to read your Cummins/Onan serial & model number →

Typical fuel consumption for 25–30 kW Bi-Fuel (NG/LP) generators →

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Specifications

FuelNatural Gas / Propane
Frequency60.0 Hz
Standby power25 kW
Standby kVA25
EmissionsEPA Emergency Stationary
ControllerPowerCommand 1.1
AlternatorCA Series (Class H insulation)
Voltage options120/240 V
Phase1
Rated current104.2 A
Circuit breaker150 A
Battery cranking550 CCA
Battery voltage12 V
Battery quantity1
Max ambient40 °C
Dimensions (L×W×H)1829×864×1156 mm
Dry weight503 kg
Sound level64.0 dBA @ 7 m

Engine

Cummins/Onan QSJ2.4
Coolant capacity12.8 L
Displacement2.4 L
AspirationNaturally aspirated or turbocharged (varies by generator set model)
Rated speed1800 rpm

Maintenance & consumables

for the Cummins/Onan QSJ2.4
ItemSpecCapacityPart #Interval
Fuel filterEvery 500 hours of operation or as needed, whichever comes first—500 hr
Oil filterEvery 1000 hours of operation or as needed, whichever comes first—1000 hr
BatteryAs needed—
Oil500 miles or 6 months, whichever comes first—804 hr

Service specifications

2
TypeItemValueUnitCondition
PressureFuel supply pressure - maximum3.5kPa
PressureFuel supply pressure - minimum1.5kPa

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

VoltagePhaseConnectionLeadsNotes
120/208312-lead12
120/24014-lead4
120/240312-lead12

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Common questions

What size generator is the Cummins/Onan RS 25?

The Cummins/Onan RS 25 is rated 25 kW standby (25.0 kVA).

Which engine powers the Cummins/Onan RS 25?

The Cummins/Onan RS 25 is powered by the Cummins/Onan QSJ2.4 engine.

What kind of fuel does the Cummins/Onan RS 25 run on?

The Cummins/Onan RS 25 runs on Natural Gas / Propane.

What is the cooling system capacity of the Cummins/Onan RS 25?

The Cummins/Onan RS 25 cooling system holds 12.8 liters (3.4 US gallons) for the engine, per the manufacturer specification sheet.

How loud is the Cummins/Onan RS 25?

The Cummins/Onan RS 25 is rated at 64.0 dBA at 7 m, per the manufacturer specification sheet.

What is the dry weight of the Cummins/Onan RS 25?

The Cummins/Onan RS 25 has a dry weight of 503 kg (1108 lb).

What voltage does the Cummins/Onan RS 25 produce?

The Cummins/Onan RS 25 is offered in 120/240 V, 1-phase.

What size battery does the Cummins/Onan RS 25 need?

The Cummins/Onan RS 25 uses 1 battery, 12 V each, 550 CCA, per the manufacturer specification sheet.

Which alternator is fitted to the Cummins/Onan RS 25?

The Cummins/Onan RS 25 uses a CA Series alternator. Insulation class H.

Parts

13
Part #DescriptionQtySystem
A046N983Preventive Maintenance Kit –Heavy Duty2Air filter Amazon eBay
A046N985Preventive Maintenance Kit (Normal Duty Air Filter)2Air filter Amazon eBay
A046N987Preventive Maintenance Kit (Normal Duty Air Filter)2Air filter Amazon eBay
CA115-T12Large, Oil CoolerOil filter Amazon eBay
CA135-E12Large, Oil CoolerOil filter Amazon eBay
A046J612Base Barrier – Elevated Genset1Service part / kit Amazon eBay
A046L270Instruction Sheet1Service part / kit Amazon eBay
CA115-H14SmallService part / kit Amazon eBay
CA115-J12SmallService part / kit Amazon eBay
CA115-L14SmallService part / kit Amazon eBay
CA115-M12LargeService part / kit Amazon eBay
CA115-P12LargeService part / kit Amazon eBay
CA115-R12LargeService part / kit Amazon eBay

Service, wear & replacement parts referenced for this model and its engine — confirm the exact part for your serial number. See the full parts catalog to search and cross-reference.

Fuel consumption

RatingLoadL/hgal/h
Standby25%5.31.4
Standby50%7.952.1
Standby75%10.62.8
Standby100%13.253.5

Available documents

Spec sheet (Cummins/Onan)Spec sheet — NAS-5775-EN (Cummins/Onan)Reference (Cummins/Onan)

This page was generated from the 3 manufacturer documents above by automated extraction; every figure shown is copied from one of them. How the data is compiled.