How to select the right generator ?

In de category How do I select the right machine ?

Just like qualifying and selecting a standby generator system contractor, the proper generator size selection is important. Spending money on a standby generator system that won't perform when called upon can be a very disappointing and expensive experience. Please review the next section to help avoid this expensive mistake



Emergency power systems are available in a variety of different sizes from 5KW-50KW and larger. Your choice will depend on the wattage requirements of the critical loads protecting your home or business.


Selecting the proper size unit for the electrical loads to be served is the most important step in providing a reliable standby generator system.


Generator under-sizing is one of the most fundamental and common mistakes made by those unfamiliar with sizing techniques and formulas.


For example, when calculating the generator load wattage for an average home 230 volt service, you may have an application where one or both of the following two conditions might apply:


Condition #1 - No motor loads will be included:


In this case, the total nameplate wattage of the appliances and lights can be used to calculate the size of the generator. To demonstrate, ten 100 watt light bulbs, a 1200 watt coffee pot, a 1250 watt toaster and a 1500 watt hair dryer would require a 5 kW generator.


Condition #2 - Motor loads will be included:


Where motor loads need to be included, the motor starting wattage must be taken into account so the generator can provide sufficient starting current. Generally, these devices normally require 5 to 6 times the listed watts (exceptions are the ultra modern frequency controlled E motor such as in air compressors) or full load current to start. A 25% factor is recommended to support electrical appliances, which are equipped with induction motors.


In this example, if the nameplate on your furnace (not air conditioner) indicates it is equipped with a blower motor and the nameplate amperage is 4,5 amps at 230 volts, the running load of this motor is 1035 watts. When the motor is started, the generator will be required to provide 4000 to 6000 watts or 4-6KW., just for this single motor.


The generator capacity is commonly specified in kVA, devide therefor the kW by 0.8 and you will find the kVA required (rule of thumb)


Should you have difficulty selection the right sized generator, please contact us for free advise +32 56 61 67 01 or send an email to sales@machinery resale.be


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