Overview#
The Cummins C100 N6 is a 100 kW (125 kVA) standby natural gas generator set powered by the QSJ5.9G-G3 -- a 5.9-liter, inline-6-cylinder, turbocharged and aftercooled spark-ignited engine producing 121.3 kWm (162.7 bhp) gross output. The C100 N6 carries EPA certification for stationary emergency use and is rated for both natural gas and propane vapor (field selectable). It is one of the most common natural gas standby units in light commercial and small industrial installations in North America.
The generator set is rated at 100 kW / 125 kVA at 0.8 power factor with both natural gas and propane fuel types delivering identical standby output. The cooling system is designed for 50 C (122 F) ambient operation. Fuel consumption at full standby load is 1,290 CFH on natural gas. The unit operates at 1800 rpm with an overspeed trip at 2250 rpm.
The C100 N6 is widely deployed in commercial office buildings, retail centers, medical clinics, light manufacturing facilities, and multi-family residential complexes where 100 kW provides sufficient emergency capacity for life safety and critical loads. Its compact footprint (under 2,900 lbs wet weight) and multiple voltage configurations make it straightforward to integrate into existing electrical infrastructure.
Technical Specifications#
| Parameter | Value |
|---|---|
| Standby Rating | 100 kW (125 kVA) |
| Frequency | 60 Hz |
| Power Factor | 0.8 |
| Engine Model | QSJ5.9G-G3 |
| Displacement | 5.9 liters |
| Configuration | Cast iron, in-line 6 cylinder |
| Aspiration | Turbocharged and aftercooled |
| Bore x Stroke | 102.1 mm x 119.9 mm (4.02 x 4.72 in) |
| Gross Engine Output | 121.3 kWm (162.7 bhp) |
| Compression Ratio | 8.5:1 |
| Rated Speed | 1800 rpm |
| Overspeed Limit | 2250 rpm |
| Lube Oil Capacity | 14.2 L (15 qt) |
| Starting System | 12 VDC, negative ground |
| Battery Capacity | 850 CCA at 0 F to 32 F ambient |
| Battery Charging Alternator | 52 amps |
| Cooling Ambient Design | 50 C (122 F) |
| Coolant Capacity (with radiator) | 16 L (4.2 US gal) |
| Cooling System Air Flow | 218.0 m³/min (7,700 scfm) |
| Unit Dry Weight | 1,276 kg (2,812 lbs) |
| Unit Wet Weight | 1,315 kg (2,898 lbs) |
Natural gas fuel consumption (CFH):
| Load | CFH | m³/hr |
|---|---|---|
| 25% | 538 | 15.2 |
| 50% | 788 | 22.3 |
| 75% | 1,028 | 29.1 |
| 100% | 1,290 | 36.5 |
Fuel inlet pressure: 6.0 to 13.0 in H₂O (1.5 to 3.2 kPa) at the engine connection.
Available voltage configurations:
- 1-phase: 120/240V (full output, reconnectable)
- 3-phase: 120/208V, 120/240V, 127/220V, 277/480V, 347/600V
Exhaust data (natural gas, standby):
- Exhaust flow at rated load: 27.3 m³/min (965 cfm)
- Exhaust temperature at rated load: 635 C (1175 F)
- Maximum allowable back pressure: 8.5 kPa (34.1 in H₂O)
Our Service Experience#
The QSJ5.9G-G3 is one of the most field-proven natural gas generator engines in the 75-125 kW class. Parts availability is excellent through the Cummins distributor network, and most technicians familiar with the QSB diesel family adapt quickly to the gas variant. The 12V single-battery starting system is simple and reliable, but battery condition should be load-tested annually -- fail-to-start events caused by a weak battery are the most common service call we see on these units.
The fuel pressure specification (6-13 in H₂O) must be confirmed under operating load conditions, not static. We have seen installations where static gas pressure is adequate but dynamic pressure drops below 6 in H₂O when the generator picks up full load, causing lean-running and speed droop. Always verify with a manometer at the engine inlet under operating conditions. The air-fuel mixer is the next most common wear item -- we typically see it requiring adjustment or replacement around 15,000-18,000 hours.
Frequently Asked Questions#
What is the standby rating of the C100 N6? 100 kW (125 kVA) at 60 Hz, 0.8 power factor. The rating is identical for natural gas and propane vapor fuel types. This is an Emergency Standby Power (ESP) rating per ISO 8528 -- no sustained overload capability is available.
What engine does the C100 N6 use? The Cummins QSJ5.9G-G3 -- a 5.9-liter, in-line 6-cylinder, turbocharged and aftercooled spark-ignited gas engine. Bore is 102.1 mm (4.02 in), stroke is 119.9 mm (4.72 in), compression ratio is 8.5:1. Gross output is 121.3 kWm (162.7 bhp) at 1800 rpm.
How much natural gas does the C100 N6 consume? At 100% standby load: 1,290 CFH. At 75%: 1,028 CFH. At 50%: 788 CFH. At 25%: 538 CFH. These values are based on 905 Btu/ft³ natural gas. The fuel inlet must maintain 6.0 to 13.0 in H₂O under all operating conditions.
What control system does the C100 N6 use? The generator is equipped with a PowerCommand control system providing isochronous governing, three-phase voltage regulation, AmpSentry alternator protection, and NFPA 110 Level 1 compliance capability. InPower PC-based service tooling is available for diagnostics and data logging.
What voltages does the C100 N6 support? Three-phase: 120/208V, 120/240V, 127/220V, 277/480V, and 347/600V. Single-phase: 120/240V (full output). The 12-lead alternator is reconnectable for field voltage configuration.
What does the C100 N6 weigh? Unit dry weight is 1,276 kg (2,812 lbs); wet weight (with coolant and oil) is 1,315 kg (2,898 lbs). These figures are for a set with standard features -- configurations with enclosures, circuit breakers, or other accessories will be heavier.
