A practical process for turning an equipment list into a dependable generator specification. This guide supports early planning; the final generator and electrical installation should be checked against the actual equipment, site conditions and duty.
Build a load schedule
List every essential load with voltage, phase, running kW or amps, power factor and starting method. Note which loads operate together and which can be delayed.
Model starting and step loads
Identify the largest motor, compressor, lift, pump, transformer or UPS input. Check starting current, acceptable voltage dip and recovery, not only steady demand.
Choose the duty rating
Compare prime with prime and standby with standby. Operating hours, average load, overload expectations and maintenance windows determine the correct rating basis.
Allow sensible headroom
Include credible growth and environmental derating without selecting a set so large that it spends most of its life at very light load.
Design the complete system
Confirm voltage, phase, controls, transfer switching, fuel autonomy, ventilation, exhaust, acoustics, foundations, cables, protection, earthing and service access.
Verify before handover
Commission controls and protection, prove transfer sequences and use load-bank or site-load testing appropriate to the project.
Start with operation, not a catalogue number
Define what the generator must achieve during a mains failure or prime-power period. A life-safety standby system, a farm protecting refrigeration and a factory maintaining selected production loads can have similar arithmetic demand but very different requirements for starting, redundancy and permissible interruption. Record the required runtime, expected frequency of operation and any loads that may be shed.
Turn nameplates into a usable schedule
Where possible, use measured current and operating data as well as equipment nameplates. Nameplates show a safe rating rather than the demand at every operating point. For planned equipment, obtain manufacturer data. Divide the schedule by phase and identify seasonal or process combinations that create the credible maximum. The result should be traceable so assumptions can be reviewed before purchase.
Avoid the two common sizing extremes
Undersizing can cause poor frequency recovery, excessive voltage dip, overheating or nuisance trips. Oversizing increases capital cost and can leave a diesel engine operating for long periods at an inefficiently light load. A sensible selection balances transient performance, steady loading, environmental derating and realistic future growth, then verifies that balance against manufacturer data.
Information to send with an enquiry
Share the site location, required voltage and phase, intended prime or standby duty, expected running hours and a schedule of the equipment to be powered. Include motor starting methods, UPS or variable-speed-drive data, the largest load step, fuel-runtime target, noise constraints and the proposed installation position where known. Photographs, electrical drawings and measured load information help the team distinguish firm requirements from early assumptions. FW Power can then discuss an appropriate generator, control arrangement, delivery, installation, commissioning and ongoing service scope without treating a guide calculation as a finished design.