Purchasing a genset that fits in with your requirements is very critical. An incorrect one will not be able to take the load and give you the value you want besides damaging some appliances in some cases.

There are plenty of choices among generator sets. Choosing a single phase, 3-phase, kVA, standby or motor depends on knowing what determines the generator capacity and a few other essential details.

Below are 3 key points to remember before determining what rating to use

AMOUNT OF POWER

It is often assumed that small generators can be used as standbys. On the contrary, this gives rise to underrating which is bad to the generator itself causing damage, as well as impacts other appliances connected to it. This is also hazardous, limits overall unit productivity and other activities.

RIGHT CAPACITY

While a generator technician is the best person to determine the exact capacity of the DG set that is required for your home, you too can determine the rating calculating the wattage of your devices

UNDERSTAND YOUR REQUIREMENTS

Buying the cheapest generator, or something that has been advocated to you isn’t always the best decision. Take the time to understand your power requirements before making a choice.

YOU WILL NEED

• List of appliances/devices that are to be powered by the generator – This is very important because it helps to accurately calculate the wattage of the generator to be used.
• Starting and running wattage of the individual items – This will often be found in the user manual of every device.
• Total power requirements calculated in kVA or KW – Power value of tools are often given in ampere. This has to be converted to watts using the following calculation

For resistive load: Wattage = amperes x volts

For reactive load: Wattage = (amperes x volts) x load factor

It is very crucial to select the right capacity DG set for many different reasons, primary among them being damage to the electrical circuitry because of load miscalculation.

ADVANTAGES OF SELECTING THE RIGHT CAPACITY DG SET

• Prevents unexpected system failures
• Increases lifespan of generator
• Minimal shutdowns because of capacity overload
• Better maintenance
• Assured personal safety
• Minimal asset damage

UNDERSTANDING GENERATORS

• Too small a generator will cause voltage fluctuations and damage to the generator or equipment windings.
• Too large a generator will cause to glaze and carbon up, due to engine loading.
• Generator capacity depends on different factors and must be done optimally to ensure the right one is selected.

RULE OF THUMB

Note 1 D.O.L – Direct On line starting (high current starting).
Note 2 S.D. – Star Delta (smooth starting med-high current).
Note 3 – A dummy load or extra load will need to be applied to avoid glazing once running.

1. One horse power (1hp) equals 0.75 kilowatt i.e. 20hp x0.75 – 15kW
2. Warm generator up before applying load
3. Always engage load from largest to smallest
4. Have an electrician balance the load across all phase loads
5. When motor is operating, after start, requirement will be 1kva for 1hp i.e. 20hp – 20kva used when  running.
6. Rating of the generator per phase = ova x 1.39. i.e. 20kva = 28amps/phase over 3 phases.

Load capacities of appliances in a home vary and not all of us are very aware. Below is a handy guide on appliance type, its wattage and how you can select the right capacity of generator for your requirement.