Buyer’s Guide

Recommended steps to follow

  1. Have a Load Test performed by an electrician with a power analyser or provide the Amps for the main circuit breaker on the loads you want to run
  2. Determine what loads need to run during an outage
  3. Determine if the generator needs to started manually or automatically during a power outage.

If automatic:

  1. De-rate the generator for altitude if needed
  2. Find a suitable installation location

Selecting the correct generator size

  • Confirm the source voltage of your mains supply voltage, i.e. Single phase 220V or three phase 380-400V
  • Check if it is necessary to operate all your loads or only certain loads
  • It is important to size appropriately for heavy use as electric motors can use up to 7x running power to start up. You will need to identify the starting method of the electric motor.

Generator location

  • Generators need to be de-rated for altitude to ensure required output.

Gauteng is at 1700 meters above sea-level.

  • A generator produces exhaust fumes during operation therefore a location where the generator is to be installed must comply with health and safety regulations and by-laws.
  • The ambient temperature can affect the generators performance. If the generator will operate at an ambient temp above 40°C, then a suitable radiator and alternator will need to be selected.
  • For canopy-type, silent generators the location needs to ensure that he correct air-flow to generator is kept cool during running conditions at an optimal level.
  • If the generator is installed outdoors, it is recommended to keep it under cover.
  • For generators installed in a generator plant room, you need to ensure that the exhaust is extended out of the room and that there is good ventilation to expel the hot air and allow the intake of cool air.
  • Install the generator as close to the main distribution board as possible to avoid costly cable lengths.
  • Sufficient space needs to be allowed for to open the doors for the servicing of the generator. (Approximately 1metre on either side of the generator set).

Generator Installation

  • Installations need to be undertaken by a qualified electrician, preferably with experience working with large generator sets which is a requirement for insurance and for generator warranty purposes.
  • Bonded neutral earthing has to be done according to the applicable South African regulations between the generator, ATS and mains incoming supply.
  • Communications cable must be of the shielded type to avoid harmonic interference.
  • Surge protection is recommended to be installed on the mains incoming feed to avoid the damage of equipment through over voltage, as well as in the situation when an Automatic Transfer Switch (ATS) is used, as the ATS is setup to sense voltage dips which switches the ATS.
  • The copper cable used must have a cross-diagonal section large enough to handle the amount of current without overheating up as per the South African regulations.
  • An important point is to confirm the phase rotation is checked during the installation as this will determine the direction in of equipment.
  • A Certificate of Compliance (COC) needs to be issued by the electrician after installation has been completed for the handover of the generator.
  • The generator must be placed on a surface that will be level and be able to handle the impact of the weight over time, as well as for fuels and oils to be level.

A reinforced concrete slab is recommended especially for large generators.

Assistance can be provided by PowerStep for this task.

Generator Running Conditions

  • Generators are designed to run optimally at an average load of 70 – 80% load for the best fuel consumption and life of the generator.
  • Running the generator at low load (< 40%) can cause damage to the engine over time, while consistently overloading the generator or switches all load simultaneously can cause start-up problems with the generator.

Generator Maintenance

  • Generators should be serviced once a year for stand-by applications or every 250 hrs, whichever comes first.
  • This is also required for the validity of the generator warranty.
  • Monthly checks and a basic generator should be conducted to confirm the generator is working.
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