Gillette · PR Series (Prime Gas)

Gillette PR-3500

350 kW standby · Natural Gas · Liquid-cooled

350 kW prime-rated natural gas generator. PSI 21.9L V12 turbocharged, Stamford S4L1DG alternator, DSE 7420. Continuous duty, 3-phase only. Made in USA.

Gillette Gillette PR-3500 generator — specifications and details
Standby power
350 kW / 350 kW prime
Voltage options
120/208V, 120/240V, 277/480V, 346/600V
Frequency / Phase
60 Hz · 3-phase
Engine
PSI 21.9L V12 TCAC · 21.9L
EPA / Emissions
EPA Stationary Spark Ignition
Alternator
Stamford S4L1DF-311
prime-powerremote-siteminingManufacturingoff-gridCommercial
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Overview#

The Gillette PR-3500 is a 350-kilowatt prime-rated natural gas generator on PSI's 21.9L turbocharged V12 — the same engine as the SP-4000/5000 standby series. At 350 kW prime (550 bhp), the V12 runs at conservative loading for unlimited continuous duty. DSE 7420 controller, Stamford S4L1DG alternator.

The V12 at continuous duty — 12-cylinder maintenance reality#

12 cylinders under continuous operation means 12-cylinder ignition service every ~6 weeks (1000 hours). This is a multi-technician, planned maintenance event. The PSI 21.9L V12 at 350 kW prime operates at 550 bhp — 28% below its standby capability — providing excellent thermal margin for sustained operation.

Our service experience#

The PSI V12 at prime duty requires rigorous scheduling discipline. We allocate dedicated service windows for the 12-cylinder ignition service, oil change (49 qt with filters), and air filter replacement at each 250/500/1000-hour interval. The engine is reliable at 350 kW continuous when maintained on schedule.

Engineering specifications

Physical

Length
168 in
Width
82 in
Height
92 in
Wet weight
9,550 lb

Acoustic

Sound @ 7m, full load
81 dBA
Enclosure
Sound-attenuated

Fuel system & runtime

BTU/hr @ full load
4,623,000

Photos

Gillette PR-3500 — product photo

Documents & downloads

Spec sheets & manuals

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Estimate runtime for the Gillette PR-3500

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

3,675,000 BTU/hr≈ 3675.0 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 Gillette PR-3500 under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter
Every 250 hours or 6 months
Coolant change
Every 4000 hours
Air filter
Every 500 hours
Spark plugs
Every 1000 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.

ComponentSymptomTypical hoursSeverity
TurbochargerPower loss from continuous high-output duty10,000+moderate
Spark plugs / ignitionMisfire, rough running under sustained load1,000+moderate
Oil degradationAccelerated valve train wear from continuous duty250+minor

Frequently Asked Questions

Is this the same 21.9L V12 as the SP-4000/5000 standby?
Yes — same PSI 21.9L V12 TCAC engine. The SP-4000 is 400 kW standby, SP-5000 is 500 kW standby. The PR-3500 at 350 kW prime is derated for unlimited continuous operation (550 bhp vs 684-764 bhp standby).
What fuel consumption at 350 kW prime?
4,623 ft3/hr NG at full load. At 75%: 3,556 ft3/hr. At 50%: 2,607 ft3/hr. At 24/7 operation, this requires a high-capacity commercial gas service — coordinate with your utility for sustained continuous supply.

Compatible equipment

Controllers

Transfer switches

More in the PR Series (Prime Gas)

80–540 kW natural gas prime power on PSI engines — continuous duty for remote sites, mining, and off-grid operations.

View all 7models in this series →

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