Cummins · Cummins D6 Commercial Diesel

Cummins C800 D6

800 kW standby / 727 kW prime · Diesel · Liquid-cooled

800 kW diesel standby generator with QSK23-G3 23.1L inline-6 engine and HPI-PT fuel injection. PowerCommand control, liquid-cooled, for data center, hospital, and mission-critical standby applications.

Cummins Cummins C800 D6 generator — specifications and details
Standby power
800 kW / 727 kW prime
Voltage options
277/480V, 346/600V, 4160V
Frequency / Phase
60 Hz · 3-phase
Engine
Cummins QSK23-G3 · 23.1L
EPA / Emissions
Tier 2
CommercialManufacturingData CentersHealthcareparalleling-array
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Overview#

The Cummins C800 D6 is an 800 kW standby diesel generator set powered by the QSK23-G3 -- a 23.1-liter, inline-6-cylinder diesel engine with Cummins' HPI-PT fuel injection. Rated at 1000 kVA standby and 909 kVA prime at 60 Hz, the C800 D6 is the top of the QSK23 power band and one of the most popular models in Cummins' large commercial diesel lineup.

The QSK23-G3 at 800 kW delivers a full megawatt of apparent power (1000 kVA) in a single inline-6 package -- a significant capability for sites that need near-megawatt standby without stepping up to a V-12 platform. The HPI-PT fuel system is proven and field-serviceable, and the 40,000-hour major overhaul interval is among the longest in the industry for this power class. CTT turbocharging provides the boost required for 100% load acceptance within 10 seconds per NFPA 110.

Medium-voltage options (4160V) and PowerCommand 2.3/3.3 paralleling controllers make the C800 D6 a common choice for multi-genset arrays in data centers and hospital campuses. For sites that need more than 800 kW per unit, the next step is the QST30-powered C900 D6 or QSK38-powered C1100 D6.

Engineering specifications

Physical

Length
117 in
Width
65 in
Height
77 in
Dry weight
7,154 lb

Fuel system & runtime

Fuel use @ full load
56 GPH
Fuel use @ 75% load
37 GPH
Fuel use @ 50% load
26 GPH

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Estimate runtime for the Cummins C800 D6

Adjust load percent and tank size to estimate runtime. Pre-filled with this model's spec where available.

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Estimated runtime

4.6 hours(0.2 days)

Fuel consumption ≈ 43.20 GPH at 75% load. Estimate based on industry-typical 1800 RPM standby curves (≈0.07 GPH/kW at full load). Actual consumption varies by engine, ambient temperature, fuel quality, and tuning.

Service intervals

Manufacturer-recommended intervals for the Cummins C800 D6 under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter
Every 500 hours or 12 months
Air filter
Every 1000 hours
Fuel filter
Every 500 hours
Major overhaul
≈ 40,000 hours

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.

ComponentSymptomTypical hoursSeverity
HPI-PT fuel injection systemRough running, power loss, injection timing drift—moderate
CTT HX82 turbochargerReduced boost, excessive smoke, turbo bearing noise—moderate
Fuel quality / tank degradationFilter clogging, hard starting, injector fouling from stagnant fuel—moderate
Starting system (24V battery bank)Slow crank, failed start requirement on infrequently exercised units—minor

Frequently Asked Questions

What engine does the Cummins C800 D6 use?
The C800 D6 uses the Cummins QSK23-G3 -- a 23.1-liter, inline-6-cylinder diesel with HPI-PT (Hydraulic Pressure Intensifier - Pre-combustion Technology) fuel injection. This is the same engine as the C750 D6, calibrated to deliver 800 kW at standby rating.
What are the standby and prime ratings of the C800 D6?
Standby rating is 800 kW (1000 kVA) at 60 Hz, 0.8 power factor. Prime rating is 727 kW (909 kVA). Both at 1800 rpm, 60 Hz, three-phase.
What are the service intervals for the C800 D6?
Oil and filter changes are due at 500 hours or 12 months. Air filter replacement at 1,000-hour intervals. Fuel filter at 500 hours. Coolant flush at 6,000 hours. Major overhaul interval is 40,000 hours under standard standby duty conditions.
How does the C800 D6 compare to the C900 D6?
The C800 D6 uses the QSK23-G3 (23.1L, inline-6) while the C900 D6 steps up to the QST30-G3 (30L, V-12) platform. The QST30 is a significantly larger engine with a V-12 configuration, designed for the 900-1000 kW class. The QSK23 inline-6 offers a more compact, lighter package at 800 kW.
Can OnPoint Generators service the C800 D6 in Northern California?
Yes. OnPoint Generators provides authorized Cummins service for large commercial diesel generators across the San Francisco Bay Area and Northern California. QSK23 service requires Cummins INSITE diagnostic software for HPI-PT fuel system calibration and ECM programming.

Compatible equipment

Transfer switches

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