Caterpillar · Cat 3500 Series (Large Diesel)

Cat 3512B

1500 kW standby · Diesel · Liquid-cooled

1230-1500 kW diesel generator with Cat 3512B V-12 engine. EUI fuel system, EMCP 4.2B controller, mission-critical and standby ratings.

Caterpillar Cat 3512B generator — specifications and details
Standby power
1500 kW
Voltage options
277/480V, 2400V, 4160V, 13800V
Frequency / Phase
60 Hz · 3-phase
Engine
Caterpillar 3512B · 51.8L
CommercialData CentersHealthcareManufacturingcontinuous-powerprime-powerparalleling-array
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Overview#

The Cat 3512B is a 1,230-1,500 kW diesel generator -- the upgraded V-12 platform in Cat's 3500 Series that bridges the gap between the original 3512 and the modern C32B. With Electronic Unit Injection (EUI), the ADEM III electronic governor, and support for low, medium, and high voltage configurations up to 13,800V, the 3512B is one of Caterpillar's most versatile large diesel generator sets.

The 3512B supports four duty cycles: standby, mission critical, prime, and continuous. At the 1500 ekW mission critical standby rating, it delivers 1875 kVA at 0.8 power factor. The EMCP 4.2B controller provides full protective relaying, Modbus RTU communication, and Cat Connect remote monitoring.

EUI and the 3512B advantage#

The 3512B's Electronic Unit Injection (EUI) system represents a significant upgrade over the original 3512's Direct Unit Injection. EUI provides electronically controlled injection timing and fuel delivery, resulting in better fuel efficiency, lower emissions, and improved transient response. The ADEM III governor integrates seamlessly with the EUI system for precise speed and load control.

Key specifications from the OEM spec sheet:

  • Bore x stroke: 170 mm x 190 mm (6.69 in x 7.48 in)
  • Displacement: 51.8 L
  • Compression ratio: 14.0:1 (standard) or 15.5:1 (HD)
  • Fuel consumption at full load: 104.7 gal/hr (396.4 L/hr)
  • Dimensions: 221.9 in x 90 in x 93.2 in (L x W x H)
  • Heat rejection to coolant: 34,122 BTU/min
  • Combustion air flow: 4,788 cfm
  • Motor starting capability: 4,350 skVA at 30% voltage dip

Medium and high voltage configurations#

The 3512B is available in low voltage (380-480V), medium voltage (2400V, 4160V), and high voltage (13,800V) configurations. Medium voltage units use form-wound alternators with permanent magnet excitation and winding temperature detectors. This voltage flexibility makes the 3512B suitable for utility interconnection, large campus distribution, and industrial plant power systems where medium-voltage distribution reduces cable costs and line losses.

Our service experience#

The 3512B is a proven workhorse in data centers, hospitals, and large industrial facilities across Northern California. The EUI fuel system is reliable but requires clean fuel -- fuel polishing is essential for standby units. The dual compression ratio option (14.0:1 standard vs 15.5:1 HD) affects both performance and maintenance intervals, so it is important to know which configuration is installed. At 25,090 lbs dry weight, structural and rigging planning is critical. The 3500 Series parts commonality between the 3512B and 3516B simplifies fleet support.

Engineering specifications

Physical

Length
221.9 in
Width
90 in
Height
93.2 in
Dry weight
25,090 lb

Fuel system & runtime

Fuel use @ full load
104.7 GPH
Fuel use @ 75% load
78.2 GPH
Fuel use @ 50% load
53.1 GPH

Documents & downloads

Spec sheets & manuals

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Estimate runtime for the Cat 3512B

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

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Estimated runtime

2.5 hours(0.1 days)

Fuel consumption ≈ 80.77 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 Cat 3512B under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter
Every 500 hours or 12 months
Coolant change
Every 6000 hours
Air filter
Every 1000 hours
Fuel filter
Every 500 hours
Major overhaul
≈ 20,000 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
Fuel quality / degradationInjector fouling, EUI nozzle wear, filter clogging4,380+moderate
Turbocharger(s)Reduced power, oil in intake, turbo whine18,000+severe
Battery bank (24V)Slow crank, failed start8,760+minor
Coolant heaterCold start issues, block heater element failure10,000+minor

Frequently Asked Questions

What are the power ratings for the Cat 3512B generator?
The Cat 3512B has a minimum rating of 1230 ekW and a maximum rating of 1500 ekW at 60 Hz / 1800 rpm. The technical spec sheet shows a 1500 ekW (1875 kVA) mission critical standby rating at 480V, 0.8 power factor. It supports standby, mission critical, prime, and continuous duty cycles. Voltage options range from 380V to 13,800V.
What engine does the Cat 3512B use?
The 3512B is a V-12, four-stroke turbocharged-aftercooled diesel engine with a 170 mm bore, 190 mm stroke, and 51.8L displacement. It uses Electronic Unit Injection (EUI) and the ADEM III electronic governor. Two compression ratio options are available: 14.0:1 standard and 15.5:1 high-duty (HD).
What is the fuel consumption of the Cat 3512B?
At the 1500 ekW mission critical standby rating (480V, 60 Hz), the 3512B consumes 104.7 gal/hr at 100% load, 78.2 gal/hr at 75% load, 53.1 gal/hr at 50% load, and 32.3 gal/hr at 25% load. Fuel rates are based on No. 2 diesel fuel at 35 degrees API gravity.
How does the 3512B compare to the 3512?
The 3512B is the evolved version of the 3512 with significantly higher output: 1230-1500 kW vs the 3512's 1000 kVA class. The 3512B uses Electronic Unit Injection (EUI) vs the 3512's Direct Unit Injection, and the ADEM III electronic governor vs the Woodward 2301A. Physical dimensions are similar (222 x 90 x 93 inches), but the 3512B supports medium and high voltage configurations up to 13,800V.
What alternator options are available for the 3512B?
The 3512B offers Cat SR5 alternators in three voltage classes: Low Voltage (random wound, internal excitation, 6-lead), Medium Voltage (form wound, permanent magnet, winding temperature detectors), and High Voltage (permanent magnet, NEMA Class H insulation). Temperature rise ratings are Class H at 40C ambient: 125C prime / 150C standby.

Compatible equipment

Transfer switches

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