Overview#
The Kohler 55REOZT4 is a 47-kilowatt standby (42 kW prime) EPA Tier 4 Final diesel mobile trailer generator powered by a Kohler KDI 3404 TCR engine at 1800 RPM. The 4-cylinder, 3.4-liter charge-air-cooled engine achieves Tier 4 Final compliance via cooled EGR and Diesel Oxidation Catalyst — no DPF required. This is the largest Kohler-branded engine variant in the REOZT4 trailer lineup; the step up to 90 kW transitions to a John Deere engine platform.
The 55REOZT4 uses a brushless rare-earth permanent-magnet alternator with Kohler's Fast-Response X excitation system, providing excellent voltage response and sustained short-circuit capability — the alternator can sustain 300% of rated current for up to 10 seconds to enable downstream breakers to clear faults without collapsing the field. The Decision-Maker 3500 paralleling controller enables synchronized parallel operation for large temporary power installations. A 386-liter (102-gallon) fuel tank provides a minimum 24 hours of runtime at prime rating.
The 55REOZT4 is larger than the 35/45 models: 98.6" x 44.1" x 74.6" versus 86" x 40" x 63.9". The single-axle trailer is rated at 6,000 lb., DOT and Transport Canada compliant, with electric brakes and breakaway battery backup. Environmental containment is 125% for oil/coolant and 110% secondary for fuel.
Specifications#
| Spec | Value |
|---|---|
| Standby Power | 47 kW |
| Prime Power | 42 kW |
| Voltage | 120/208V, 120/240V, 277/480V, 347/600V |
| Frequency | 60 Hz |
| Engine | Kohler KDI 3404 TCR |
| Cylinders | 4 inline |
| Displacement | 3.4 L (207 cu. in.) |
| Aspiration | Turbocharged, Charge Air Cooled |
| Emissions | EPA Tier 4 Final (nonroad) |
| RPM | 1800 |
| Fuel | Ultra Low Sulfur Diesel / HVO / RD |
| Cooling | Liquid (unit-mounted radiator, 45°C ambient) |
| Fuel consumption — 100% load | 3.8 gph (standby) |
| Fuel consumption — 75% load | 2.9 gph (standby) |
| Fuel tank | 102 gal (386 L) — 24 hr minimum runtime |
| Sound level | 69 dB(A) @ 7 m (prime, full load) |
| Dimensions (L x W x H) | 98.6" x 44.1" x 74.6" |
| Controller | Decision-Maker 3500 |
Service & Maintenance#
Kohler's published maintenance schedule for the 55REOZT4 / KDI 3404 TCR engine:
| Service | Interval |
|---|---|
| Oil and filter change | Every 250 hours or 12 months |
| Fuel filter replacement | Every 250 hours |
| Air filter inspection/replacement | Every 500 hours |
| Coolant flush | Every 2,000 hours or 3 years |
| Load bank test | Every 12 months (NFPA 110 requirement) |
| Major overhaul | Every 8,000 hours |
Oil pan capacity with filter is 15.6 liters (16.5 quarts) — larger than the 35/45 models, so plan accordingly on service calls. Kohler specifies API CJ-4 or ACEA E6–E9 oil. The KDI 3404 TCR uses a primary 5-micron water-separator fuel filter; pay close attention to water-separator status during wet-season deployments in Northern California.
Common Failure Modes#
The 55REOZT4 shares the same Tier 4 aftertreatment profile as the 35/45 models: back-pressure and DOC monitoring will trigger derate fault codes if the aftertreatment system is not maintained and the unit is operated predominantly at light load. Running loaded exercises and avoiding extended no-load operation materially extends aftertreatment service life.
Fuel quality degradation is the primary service concern — the KDI 3404 TCR common-rail injection system is sensitive to fuel contamination. Injector fouling presents as hard starting, rough running at idle, and elevated exhaust smoke. Battery failures on standby units are the most common minor issue; the 55REOZT4 uses a single 12V 925 CCA battery, and annual battery inspection is standard practice.
Our service experience#
OnPoint Generators provides installation, maintenance, load bank testing, and emergency service for Kohler industrial generators throughout Northern California and the Central Valley. The 55REOZT4 fills the gap between the 40 kW 45REOZT4 and the 85 kW 90REOZT4 in the mobile trailer lineup, and is a common choice for planned utility outages at mid-size commercial facilities and for equipment rental fleets serving construction. Because the REOZT4 series shares engine families and controller platforms, our field teams carry cross-compatible parts for the full range.
FAQ#
What is the standby rating of the Kohler 55REOZT4?#
The 55REOZT4 is rated at 47 kW standby (58 kVA at 0.8 PF three-phase) at 120/208V. Prime power is 42 kW. All ratings are per Kohler spec sheet G5-414.
Is the 55REOZT4 a mobile or stationary generator?#
The 55REOZT4 is a trailer-mounted mobile generator, EPA Tier 4 Final certified for nonroad applications. A single-axle DOT/TC-compliant trailer with electric brakes is available as an option.
Does the 55REOZT4 require a DPF?#
No. The 55REOZT4 meets EPA Tier 4 Final without a Diesel Particulate Filter. Kohler uses cooled EGR and a Diesel Oxidation Catalyst to meet emissions requirements on the KDI 3404 TCR engine.
What is the sound level of the Kohler 55REOZT4?#
Per Kohler published specifications, the 55REOZT4 is rated at 69 dB(A) log average at 7 meters with full load at the prime rating. This is 2 dB louder than the 35REOZT4 due to the larger engine displacement.
