400 kW standby · Natural Gas / LPG · Liquid-cooled
400 kW natural gas/propane commercial standby generator. The top of Cummins' C-Series gaseous lineup for large hospitals, campuses, mission-critical, and paralleling arrays.
The Cummins C400 N6 is a 400-kilowatt natural gas and propane commercial standby generator — the largest unit in Cummins' C-Series gaseous lineup. At 400 kW, it covers the standby requirements of large hospitals, major commercial campuses, industrial facilities, and mission-critical installations where natural gas is the preferred fuel and supply continuity is not a primary constraint.
The C400 N6 is a capable paralleling platform: multiple units with PowerCommand controllers can be arrayed for facilities requiring 800 kW, 1200 kW, or higher capacities on natural gas, with load demand sequencing to maximize fuel efficiency at partial load.
The C400 N6 is our go-to recommendation for large commercial and institutional accounts that have a strong preference for gaseous fuel. At 400 kW, the turbocharged engine runs hard under full-load test conditions — thorough load bank testing at commissioning and annually is essential to verify performance. We pay close attention to gas supply pressure, turbocharger condition, and cooling system integrity on these units, as any one of those systems under-performing at full load will show up quickly.
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Adjust load percent and tank size to estimate runtime. Pre-filled with this model's spec where available.
Estimate runtime on this tank
Fuel demand at 75% load
4,200,000 BTU/hr≈ 4200.0 cf/min @ 1,000 BTU/cf
On utility natural gas the runtime is generally unlimited provided the supply line and meter can deliver this BTU/hr at the engine's required inlet pressure (typically 5–14" WC residential, up to 5 psi commercial). Confirm against the OEM's published fuel-pressure spec.
Service intervals
Manufacturer-recommended intervals for the Cummins C400 N6 under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.
Oil & filter
Every 250 hours or 12 months
Coolant change
Every 4000 hours
Air filter
Every 1000 hours
Spark plugs
Every 1500 hours
Major overhaul
≈ 15,000 hours
Load bank test
Every 12 months
Common failure modes
What we've seen fail on this platform. Use as a service-planning reference, not a diagnostic — actual failure modes depend heavily on duty cycle and maintenance history.
Component
Symptom
Typical hours
Severity
Turbocharger
Loss of power, excessive smoke under load
12,000+
moderate
Spark plugs / ignition
Misfire at load, rough running
1,500+
minor
Charge air cooler
Reduced power output, elevated intake temps
10,000+
moderate
Battery
Failed to start during outage
8,760+
minor
Frequently Asked Questions
What is the largest Cummins C-Series gaseous generator?
The C400 N6 is at the top of the C-Series commercial gaseous lineup at 400 kW. For standby loads beyond 400 kW on natural gas, facilities typically move to parallel arrays of C400 N6 units with PowerCommand controllers coordinating load sharing, or consider Cummins' industrial gaseous platforms.
Is the C400 N6 approved for NFPA 110 Level 1 healthcare standby?
The C400 N6 is UL 2200 listed and can meet NFPA 110 Level 1 performance requirements when properly installed. Healthcare applications require confirmation from the AHJ and the facility's engineer of record. Natural gas dependency is a key risk factor — many healthcare codes mandate diesel for primary life-safety coverage in seismic zones or areas prone to gas supply interruptions.
How does paralleling C400 N6 units compare to a single large diesel?
Paralleling multiple C400 N6 units provides N+1 redundancy, scalability, and the operational benefit of gaseous fuel. The trade-off vs. a single large diesel is increased switchgear complexity and dependency on gas supply continuity. For mission-critical applications where the utility gas supply could be compromised in the same disaster that caused the grid outage, diesel remains the more resilient choice.
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250 kW standby · Natural Gas / LPG · Liquid-cooled
250 kW natural gas/propane commercial standby generator. Large-format turbocharged C-Series gaseous platform for hospitals, campuses, and industrial facilities.