Buying diesel generating sets from China: ratings, the offer, the factory test and shipping

This guide covers diesel generating sets from about 20 kVA to a few megawatts, open-frame, canopied or containerised, bought from Chinese assemblers for construction sites, plants, hospitals, telecom sites and off-grid installations. It follows the order of a purchase: the rating, the offer, the checks before payment, the factory test and the shipment.

Start with the rating: prime or standby

ISO 8528-1 defines the ratings of a generating set; the four main ones are below. The same set carries different figures depending on how it will run, so two offers are only comparable when they quote the same rating.

Standby is the larger number on the datasheet, so it is the one some offers lead with. A set that will be the only supply of a site must be sized on prime power. Many engine makers allow 10% over prime power for one hour in twelve; a standby rating usually allows no overload.

The rating is given in kVA at a power factor of 0.8 lagging, so a 500 kVA set gives 400 kW. Motors, pumps and compressors draw reactive current and a high current when they start: the kVA rating, and the alternator behind it, decide whether the set can start your largest motor without the voltage collapsing.

Datasheet ratings hold at standard reference conditions, set by ISO 3046-1 at 25 °C, 100 kPa and 30% relative humidity. Above the altitude and temperature the engine maker states, the output must be derated. For a site at 40 °C or more, ask for the derated output at the site’s conditions and for the radiator’s design ambient temperature: the offer should state both.

Performance class: how well the set holds voltage and frequency

ISO 8528-5 sets four performance classes, G1 to G4, for how far voltage and frequency may move when load is added or removed, and how fast they must recover. G1 suits simple loads such as lighting and heating, G2 general loads with pumps and fans, G3 telecom and thyristor-controlled loads, and G4 the most sensitive loads, such as data processing. Name the class in the specification: it decides the governor, the voltage regulator and the size of the load steps the set must accept. Most turbocharged engines cannot take their full load in one step; ISO 8528-5 gives guide values and the engine maker states the steps the engine accepts.

What the offer must state

When two offers differ only in price, check the engine and alternator first. A lower price often means a different engine series, a smaller alternator than the kVA rating needs, or a radiator rated for a cooler climate than the site.

Check the dataplates before you pay

Ask for photos of the engine, alternator and controller dataplates of the actual units on your order, not catalogue pictures. Each dataplate shows a model, a serial number, a rating and a date. The engine serial number can be checked with the engine maker’s service network, and the dates show whether a unit offered as new production has been in stock for years. A plant that cannot photograph the dataplates before the order may not have the units yet: ask for the production lead time in writing instead of a promise that the sets are in stock. The engine makers page shows who makes each engine family and what each maker lets you check.

The factory load test

Every set should be run on a load bank at the plant before it ships. ISO 8528-6 describes the test methods; the programme the contract names sets the steps, the hold times and the overload. A typical programme looks like this:

At each step the readings are recorded: voltage, frequency, current, kW, kVA and power factor, coolant temperature and oil pressure. The protections are then triggered one by one (low oil pressure, high coolant temperature, overspeed, emergency stop) to show that the set shuts down as it should.

Ask which load bank the plant will use. A resistive load bank works at a power factor of 1.0: it loads the engine to its full kW, but the alternator then carries only about 80% of its rated current, and the alternator’s excitation is never pushed to the level a 0.8 power-factor site load demands. A resistive-reactive load bank at 0.8 power factor tests the set at its full kVA. Many plants have resistive load banks only. If yours does, agree in writing what the test proves and what is left for the site test. For a critical set, a witnessed generator FAT ties every reading to the serial numbers on your order.

Selling into the EU

A generating set placed on the EU market is machinery. A mobile or transportable set needs an engine with EU emissions type-approval under Regulation (EU) 2016/1628 (Stage V); a permanently installed set is outside that regulation, though national rules, or Directive (EU) 2015/2193 on medium combustion plants from 1 MW thermal input, may apply. Sets of less than 400 kW also fall under the outdoor noise Directive 2000/14/EC, with a guaranteed sound power level on the marking. The machinery rules change on 20 January 2027: see the guide to the EU Machinery Regulation 2023/1230. Outside the EU, check the destination’s own rules before ordering.

Shipping

Open-frame sets of a few hundred kVA usually travel in a 20 ft or 40 ft container; a containerised set can travel as its own container when it carries a valid CSC safety-approval plate, and otherwise goes on a flat rack or as breakbulk. Ask the forwarder how they will declare the set before booking. Many accept generating sets as general cargo only with the fuel tank drained and the battery removed or disconnected; a set shipped with fuel or a fitted battery can be declared as dangerous goods. The guide to shipping industrial equipment from China covers the delivery terms and the dangerous-goods screen.

What moves the price and the lead time

• the engine make and series, and the alternator behind it;
• prime or standby rating, and derating for the site’s heat and altitude;
• open frame, canopy or container, and the sound level required;
• the controller, and whether sets must synchronise;
• fuel tank size, transfer switch, spare parts and tools;
• the test programme: load steps, overload, power factor, witness;
• emissions and noise rules at the destination, packing and the delivery term.

Buyer checklist

Before award

• Rating in kVA and kW at 0.8 power factor, prime or standby, at the site’s temperature and altitude.
• Engine, alternator and controller by make, model and production plant.
• Performance class under ISO 8528-5 and the largest motor the set must start.
• Scope: canopy or container, sound level, fuel tank, transfer switch, spares.
• Factory test programme, load bank type and power factor, and the right to witness.

Before shipment

• Dataplates and serial numbers of the engine, alternator and controller checked against the order.
• The load test with readings at every step, witnessed where the order is critical: see generator FAT witnessing.
• Wiring diagrams, manuals and the spare-parts list in the site’s language.
• How the forwarder will declare the set: fuel drained, battery removed or disconnected.

Frequently asked questions