Diesel Generator Sets from China: A Buyer's Guide to…

When buying a diesel generator set from China, specify the rating type (prime, standby or continuous) under ISO 8528, the output in kW at your site conditions, and the exact engine, alternator, controller and enclosure, because these define what the set can actually deliver. Two sets with the same kVA on the nameplate can perform very differently once the rating basis is clear.

Prime, standby and continuous ratings

ISO 8528-1 defines how generator-set power is rated. The rating you need depends on how the set will run, not on the biggest number in the brochure.

Rating	ISO 8528-1 term	Use case	Running pattern
Standby	Emergency standby power (ESP)	Back-up for mains failure in buildings, hospitals, data rooms	Limited hours per year, variable load, no overload allowed
Prime	Prime rated power (PRP)	Main power where there is no grid, or where the grid is unreliable	Unlimited hours, variable load with a limited average load factor
Limited-time	Limited-time running power (LTP)	Planned peak lopping or scheduled outages	Limited hours per year at a constant load
Continuous	Continuous operating power (COP)	Base-load plants, mines, remote sites	Unlimited hours at constant load

A set rated for standby has a higher number than the same set rated for prime. Ask every supplier to quote both values and to state which is printed on the nameplate. Comparing one supplier's standby figure with another's prime figure is the most common sizing error.

kVA vs kW

Generators are often sold in kVA, but your loads draw kW. The relationship is kW = kVA × power factor. Most generator sets are rated at a power factor of 0.8 lagging, so a 500 kVA set gives 400 kW.

Size the engine on kW (real power): the engine only produces real power.
Size the alternator on kVA (apparent power): the windings carry the full current.
Check motor starting. Large motors draw several times their running current at start-up, which causes voltage dip. Ask for a motor-starting calculation or the alternator's starting kVA at a stated voltage dip.
Derate for site conditions. Altitude and high ambient temperature reduce engine output. Give the supplier your altitude and maximum ambient temperature and ask for the derated output in writing.

Engine and alternator pairing

A generator set is an assembly. Chinese gensets are usually built by a packager who buys an engine and an alternator and mounts them on a common base frame with a radiator, controller and fuel tank. Ask the packager to confirm:

Engine make, model and its own power rating at the set's speed (1,500 rpm for 50 Hz, 1,800 rpm for 60 Hz).
Alternator make, model, insulation class, temperature rise class and IP rating.
That the engine's prime output is enough to drive the alternator at the set's prime kW, with margin for losses and the radiator fan.
Voltage regulator type (AVR), and whether a permanent magnet generator (PMG) excitation is fitted for better motor starting and non-linear loads.
Governor type (mechanical or electronic) and the ISO 8528-5 performance class offered (G1 to G4), which describes how tightly voltage and frequency recover after a load step.

Chinese engine makers are listed in the diesel engine category; compare engine data sheets directly rather than relying on the packager's summary.

Controllers and paralleling

The controller starts and protects the set and reports its status. Ask for the controller brand and model and the functions included:

Protections: low oil pressure, high coolant temperature, overspeed, over/under voltage and frequency, overcurrent and earth fault.
Metering: voltage, current, kW, kVA, power factor, hours, fuel level.
Communication: Modbus, Ethernet or remote monitoring for unattended sites.
Paralleling: if several sets will share a load or run with the grid, the controller and governor must support load sharing and synchronising.

Automatic transfer switch (ATS)

For standby use, the ATS moves the load from mains to generator and back. Agree on:

Rated current and number of poles (3-pole or 4-pole, depending on your earthing system and neutral switching).
Transfer switching equipment to IEC 60947-6-1, with mechanical and electrical interlocking.
Open transition (break before make) or closed transition, if allowed by your utility.
Whether the ATS is supplied loose, inside a separate panel, or built into the generator's control cabinet.

The ATS panel connects to your main switchboard, so align it with your distribution cabinets and cable sizes. Where only short bridging is needed for sensitive loads, an emergency power supply or UPS system often sits between the ATS and the load.

Canopy, noise and fuel

Open vs canopy: open sets go inside a plant room with its own ventilation and silencer; canopy sets are weatherproof and sound-attenuated for outdoor use.
Noise: ask for the sound pressure level in dB(A) at a stated distance (commonly 1 m or 7 m) and at a stated load. For the EU, outdoor equipment noise is regulated under Directive 2000/14/EC. Verify claims with a sound level meter at inspection.
Fuel tank: base-frame tank capacity and running hours at prime load; bunded tanks if your site rules require spill containment.
Corrosion: coastal and tropical sites need better canopy coatings and stainless fasteners.

What to check with a Chinese supplier

Find out whether the company manufactures and packages sets itself or resells another factory's product. Check its Unified Social Credit Code in the national enterprise credit system and that its business scope covers generator manufacturing. Ask for ISO 9001 certification, CE documents for Europe, the engine's emissions certificate, and a factory load-test report for a set of the same model. The company scores on our category pages reflect verifiable company data, not product quality; see the methodology for details.

Pre-shipment checklist

Load test on a resistive load bank in steps up to full rated load, with readings recorded.
Load acceptance test: apply and remove a block load and record voltage and frequency recovery.
Check all protections trip and alarm correctly.
Confirm serial numbers of engine, alternator and controller match the documents.
Check the ATS operates on simulated mains failure and restoration.
Inspect canopy seals, door locks, lifting points and fuel-tank leaks.

Frequently asked questions

Should I buy a standby or prime-rated generator?

Buy prime-rated if the set will be your main power source or will run for long periods. Standby ratings are for occasional emergency use only, and running a standby set as prime power shortens its life.

How do I convert kVA to kW for a generator?

Multiply kVA by the power factor; at the usual 0.8 power factor, 100 kVA equals 80 kW. Size the engine on kW and the alternator on kVA.

What does ISO 8528 cover?

ISO 8528 is the international series for reciprocating internal-combustion-engine generating sets. It defines ratings, performance classes and test methods, so quoting to it makes offers comparable.