Overview#
The Generac SG400 is a 400 kW standby (360 kW prime) demand response ready industrial natural gas generator set powered by Generac's 21.9L V12 turbocharged and aftercooled spark-ignited engine. Rated at 500 kVA standby at 60 Hz, it is EPA certified for both stationary emergency and non-emergency applications. Available in three-phase configurations only, it features the Generac Power Zone Pro Sync controller with a 7-inch color touchscreen display, Modbus RTU/TCP/IP, and Ethernet communications.
Engine and alternator#
The Generac 21.9L (1,336 cubic inch) V12 turbocharged/aftercooled engine delivers 400 kW standby at 589 hp and 194 psi BMEP at 1,800 RPM. The engine has a 10.0:1 compression ratio, steel crankshaft, 7 main bearings, solid lifters, cast iron cylinder heads, and cast steel alloy cylinder liners. The 24V DC electrical system uses dual 12V batteries. Crankcase capacity is 31.7 quarts (30 L). Standard operating fuel pressure is 11–14 inches of water column (with 7–11 in H2O optional configuration).
The standard alternator is the Generac K0400124Y21, a 4-pole revolving-field design with Class H insulation on both rotor and stator. It features permanent magnet excitation, full digital voltage regulation with plus or minus 0.25% steady-state accuracy, and total harmonic distortion below 5%.
Power ratings and fuel consumption#
At 277/480V three-phase and 0.8 power factor, the SG400 delivers 400 kW standby / 360 kW prime (602 A / 542 A). No single-phase configuration is available on this model.
Natural gas consumption at standby/demand response ratings: 4,620 scfh at 100% load, 3,600 scfh at 75%, 2,640 scfh at 50%, and 1,680 scfh at 25% load.
Physical dimensions#
The open set measures 154.4 x 71.0 x 66.5 inches (3,922 x 1,803 x 1,689 mm), weighing 7,286 to 8,650 lbs. Weather protected enclosure: 207.4 x 71.0 x 80.0 inches. Level 1 sound attenuated: 247.5 x 71.0 x 80.0 inches. Level 2 sound attenuated: 207.4 x 71.0 x 114.1 inches. Level 3 sound attenuated (steel only): 232.0 x 76.9 x 129.2 inches.
Our service experience#
The SG400 marks the platform transition from the 14.2L inline-6 to the 21.9L V12 — a significantly larger displacement, wider footprint (71 inches vs 57 inches for the 14.2L models), and higher fuel supply requirement (standard 11–14 in H2O). With 12 cylinders and 12 spark plugs, service time for plug replacement at 1,000-hour intervals is doubled compared to the 6-cylinder models. Exhaust temperature at 1,297 degrees F is relatively modest for the output level due to the larger displacement and more conservative BMEP. The 44-inch pusher fan at 1,404 RPM requires adequate cooling air inlet clearance.
