A good genset specification states what the set must deliver, where it will run, which rules it must meet and how it will be tested. It also lists the documents and packing you expect. Use ISO 8528 as the framework, because most builders know it and it gives you clear terms to test against.
Write the specification before you ask for quotes. Builders then quote on the same set, and you can compare them fairly. Keep it to the points that matter, and mark which items are essential and which are preferences.
Output and electrical data
- Rating in kVA and kW at 0.8 power factor, with the rating type under ISO 8528-1, such as prime or standby.
- Voltage, number of phases, frequency and connection, such as 400 V, three-phase, 50 Hz.
- Performance class under ISO 8528-5, such as G2 for general loads or G3 for sensitive loads.
- Largest motor to be started and how it starts, so the builder can size the alternator.
- Alternator insulation class, ingress protection and voltage regulation band.
Site and environment
- Maximum ambient temperature, altitude and humidity, so the builder can derate correctly.
- Indoor or outdoor use, and whether an acoustic canopy is needed.
- Maximum noise level, with the distance and measuring method.
- The emission standard the engine must meet in your market, with proof of approval.
- Fuel tank capacity or required running hours at a stated load.
Controls and protection
- Controller type, with manual start or automatic mains failure start.
- An automatic transfer switch, if the builder is to supply it.
- Shutdowns for low oil pressure, high coolant temperature, overspeed and overcurrent.
- Metering of voltage, current, frequency, power, running hours and fuel level.
- Remote monitoring or communication ports if your customers need them.
Tests, documents and packing
Specify a witnessed load test under ISO 8528-6 on every set, with stepped loads, transient response and protections checked, as covered in what a genset load test is. State the electrical standard your market applies to the control panel and wiring.
List the documents you need with each set: test report, wiring diagram, operation and service manuals, parts catalogue, alternator and engine certificates, and declarations required in your market. Then state the packing, preservation and marking rules, and the spare parts to ship with the order.
Finally, attach the warranty and acceptance terms. For the wider contract, see what an engineering purchase contract should include.
The most common gaps are a kVA figure with no rating type, no site temperature, and no agreed test. Each gap lets a builder quote a smaller or less tested set and still claim it meets your request.
Next step
We turn your requirements into a specification builders can quote on, then check that the sets match it before shipment. To start, book a free sourcing review.