Overview#
The Cat DG400 is a 400 kW natural gas generator set built on the Cat CG18 inline-6 engine platform. With EPA certification for both emergency and non-emergency operation, the DG400 is positioned for commercial standby power, demand response programs, and limited time power applications up to 500 hours per year.
The CG18 engine uses Caterpillar's ADEM A4 electronic controls with air-to-air aftercooling -- a simpler and more compact cooling arrangement than the separate-circuit aftercooling (SCAC) used on larger Cat gas engines. At 18.1 liters displacement from six cylinders, the CG18 offers strong torque density and robust load acceptance.
Power ratings#
The DG400 supports three operating modes at 60 Hz:
- Standby / Demand Response: 400 ekW (500 kVA) -- up to 500 hours/year, average load 70%
- Limited Time Power (LTP): 350 ekW (437.5 kVA) -- up to 500 hours/year, average load up to 100%
Fuel consumption#
Natural gas fuel consumption at rated load (measured in CFH at LHV of 905 BTU/SCF):
| Load | Standby | Demand Response | LTP |
|---|---|---|---|
| 100% | 4,439 | 4,573 | 4,110 |
| 75% | 3,489 | 3,626 | 3,277 |
| 50% | 2,585 | 2,677 | 2,433 |
Alternator options#
The DG400 offers extensive alternator selection across six frame sizes (LC6114B through LC6124F) with SE or AREP excitation. Temperature rise options range from 80C to 130C at 40C ambient, providing flexibility for motor starting requirements. At 480V with the LC6114F frame (80C rise), motor starting capability reaches 1,310 skVA at 30% voltage dip.
Physical specifications#
Available on narrow or wide skid bases. The narrow skid configuration (141.4 in L x 69.5 in W x 82.1 in H) at 10,337 lb dry weight is compact for the 400 kW class. The wide skid adds approximately 55 inches in length and 16 inches in width for installations requiring integral sub-base fuel tanks or additional accessories.
Our service experience#
The CG18 is a clean, well-organized engine to service. The ADEM A4 control system provides comprehensive diagnostics via Cat ET software. Key maintenance items include spark plug inspection, air-to-air aftercooler cleaning, and lube oil changes (42 liters with filter). The engine's 10.5:1 compression ratio provides good detonation margin on varying gas quality. The unit's dual EPA certification (emergency + non-emergency) makes it a revenue-generating asset for facilities participating in demand response programs.
