Section index · technical resources · 12/06/2026
Technical Documentation
A generating set produces paperwork at about the same rate as electricity, and most of it is thrown away. The documents that matter fit on one page.
This section explains what each one is for and how to read it, starting with the sizing calculation, which is the one document a buyer should produce themselves.
A generating set generates paperwork at roughly the same rate as it generates electricity, and most of it is thrown away. The documents that matter can be listed on one page, and they fall into three groups: what describes the machine before you buy it, what describes your machine after it is built, and what tells a technician how to keep it running.
This section explains what each group contains and how to use it. It is not a mirror of manufacturers' literature, it is a guide to reading it.
Before you buy: specification documents
The technical datasheet is the primary sales document and the most misread. It carries the rated output under each duty class, the engine and alternator models, fuel consumption at part loads, dimensions and dry weight, and the reference conditions everything was measured at. Reading it properly means reading the conditions first and the headline number second. The structure of these sheets is set out in the English technical datasheet page.
Alongside it sits the general arrangement drawing, which decides whether the machine physically fits and how it will be moved into place, and the sizing calculation, which should be the buyer's own rather than the supplier's. The method for producing it is in sizing a generator set for your load.
| Document | Produced by | What it is for |
|---|---|---|
| Technical datasheet | Assembler | Comparing machines before purchase |
| General arrangement drawing | Assembler | Fit, access and installation planning |
| Sizing calculation | The buyer | Justifying the rating asked for |
| Factory acceptance test report | Assembler | Evidence about your individual machine |
| Wiring and control schematics | Assembler | Fault finding and modification |
| Operation and maintenance manual | Engine maker and assembler | Intervals and procedures |
| Commissioning and load test record | Commissioning engineer | Proof the installation performs |
After it is built: evidence about your machine
The factory acceptance test report and the commissioning record are the two documents that describe the individual machine rather than the model. They record the output achieved, the behaviour under load steps, the temperatures reached and the conditions on the day. Everything else in a project file is generic by comparison, which is the argument made in the certification and standards page.
The rating plate belongs in this group too, photographed at handover along with the engine plate. Plates fade, get painted over and occasionally get swapped during a refurbishment. A photograph in the file costs nothing.
One complete document set in the site office and one in the plant room, in a sealed wallet. A schematic that lives only on a server is unavailable during the outage it was needed for, which is the one moment it exists to serve.
For running it: manuals and schedules
The engine manual governs everything about the engine, and where it disagrees with any general figure, including any figure published in this magazine, the manual wins. It carries the service intervals, the fluid specifications, the torque figures and the fault codes. The assembler's manual covers the rest of the machine: the controller, the breaker, the cooling package and the enclosure.
The practical schedules built on top of those manuals sit in the maintenance and operation section, including the interval logic in the oil change guide, which explains why the calendar limit almost always governs on standby plant.
Conversions worth having to hand
Three conversions cover most of the arithmetic in this field. Apparent power in kVA multiplied by the power factor gives real power in kW, so a 500 kVA set at 0.8 power factor delivers 400 kW. Engine mechanical output in kW is always higher than the electrical output, because of alternator losses in the region of 3 to 6 per cent. And a three-phase current is found from kVA divided by the product of the line voltage and the square root of three, which for 400 volts means roughly 1.44 amperes per kVA.
Read next
The one calculation every buyer should do themselves is in sizing a generator set for your load, with a worked example from load list to frame size.
For the datasheet structure and the figures worth extracting from it, see the English technical datasheets page.
For what the certificates in the same file actually mean, read certification and standards, and for the schedules built on the manuals, the maintenance section.