Generator questions & answers

Below please find a list of the most frequently asked generator questions and answers.

Click on the question below for an answer:

  1. What is a generator? 
  2. What size generator do you need?
  3. Wiring & connection
  4. Single phase or 3 phase?
  5. Electric start or recoil start?
  6. How much noise do generators make? 
  7. How do you install it and what does it cost?
  8. How much do generators cost to run?
  9. How much do Goscor Power Products generators cost?
  10. How do generators operate? (Step by step explanation)
  11. What can you run on a 6 KVA generator?
  12. What happens when I overload i.e. draw too much from a generator?

 

What is a generator?

An engine driven alternator producing electricity.
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What size generator do you need?

Generators are measured by their KVA (kilo volt amps).

To calculate the amps that it can produce divide KVA by 230 volts.

To calculate the wattage it can produce, multiply KVA by 80% if being used for a 3-phase alternator or by 100% for a single phase generator.

e.g. a 6KVA generator single phase:

Amps = 6000/230 = 26amps

Wattage = 6000*100% = 6000

It is important to note that this is the maximum that it can produce but not the rated amount which is normally around 90% of this. In addition to this, all engines are specified at sea level so for a generator working in Johannesburg you would need to multiply by approximately another 82% to compensate for altitude.

Therefore your 6 KVA generator in Jhb would be producing about 4,428 Watts.

I have attached a list showing the wattage required by various appliances. It is also shown on the back of most appliances. It is worth noting however that on start-up, electric motors may require up to double their wattage.

The main thing you need to consider is whether your generator is an emergency back-up in which case you don’t need to run all of your appliances e.g. geysers and heaters or whether you want a “seamless” transition from Eskom to generator without turning anything off.
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Wiring and connection

It is best to have the generator connected to your main DB board and to have a transfer switch installed.

An Automatic Transfer Switch (ATS) will turn your generator on automatically as soon as the power goes off and will turn the generator off when the power comes back on. This may seem like the solution but there are a few problems:

 

  • Do you really want your generator to turn on at 2.00 a.m. if there is an outage?
  • Most of the smaller petrol generators are gravity fed fuel systems that require you to turn the fuel off at the carburetor when not in use so if the generator turns on, you will still need to go outside to turn the fuel on.
  • The cable to the choke may rust resulting in it not being able to pull open the choke resulting in the engine not starting.
  • As all breakers would be on, there would be too much power being drawn from the generator and it would battle to start.


A manual transfer switch (MTS) is much cheaper and requires that when the power goes out, that you go to the generator, start it and then manually switch from Eskom to Generator.
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Single phase or 3 phase?

If you have 3 phase appliances e.g. borehole pump, then you will require a 3 phase generator. Otherwise as part of the installation, the "change over switch" will bridge the three phases together so that a single phase generator will be able to run a house that has 3 phase power.
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Electric start or recoil start?

An able bodied male can easily "pull start" the 5 KVA and 6 KVA generators however females battle to start them so I would suggest electric start for home use.
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How much noise do generators make?

A 6KVA generator is run by a 410cc engine that revs at 3000rpm which does make a noise – 77db. A smaller generator has a smaller engine which is quieter. Basically, there are no silent generators however some are quieter than others.
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How do you install a generator and what does it cost?

A qualified electrician would have to install the generator for you and will charge you for their time as well as the electric cable from the generator to the box.  The installation cost around R 1,500-00.

In addition to the actual installation, as the generator would have to stand outside, you would need to cover the generator so that rain does not come into contact with the electronics. 

As the engines are air-cooled they need to be well ventilated. 

Fumes from the engines are hazardous so the generator must not be run inside including running in a garage.
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How much do generators cost to run?

The petrol generators use between 1.5 liters per hour for smaller generators up to 3.5 liter per hour for the 12 KVA generators.

The larger diesel generators for home use would use around 4 liters per hour but it would depend on the size of the engine.
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How much do Goscor Power Products generators cost?

Like anything, you pay for quality and quantity. The better quality Japanese generators cost around R2,000 per KVA. Chinese generators are generally copies of other well known engines and are cheaper but then there is a quality difference particularly with regards after sales service and parts. Many generator manufacturers also exaggerate the actual KVA that their generators produce.

Electric start is about R 2000-00 more expensive than recoil start (pull start).

AVR (Automatic Voltage Regulator) is required if you are running computers without UPS and other sensitive appliances.  An AVR is a special altenator and would cost an additional R 2000-00
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How do generators operate? (Step by step explanation)

When the power goes off, first step would be to go to the DB board and turn off the geysers and anything else that you do not need for example the swimming pool pump.  Open the choke, turn on the fuel and start the generator either by turning a key (electric start) or pull starting.  Go to the MTS and swtich from ESKOM to generator.  Your house will now be supplied with electricity and you would hear the generator labouring under the load it is carrying.  You should turn off all non essential lights and other appliances.
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What can you run on a 6Kva generator?

The following can all be run at the same time on a Robin Generator (tested):
Deep freeze, 2 fridges, TV, Decoder, Lights, Alarm system, Hi-Fi and one of either kettle, hot plate or microwave.
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What happens if you overload i.e. draw too much power from a generator?

You would hear the engine of the generator labouring under the load. The alternator will then trip out, the engine will continue running and you will need to re-set the alternator by pushing a button.
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