| Ambient circumstance influence for diesel generating set |
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Humidity, height and temperature will exert influence upon generators,and it is rather complex in practice.
The following factors need considering.:
1 eroding gas in the air
2 salty water (fog) on the seaside
3 dust or sand
4 raindrop
Hence we should take the complexity of the climate into considerations. We recommend three options to get along with different weathers.
1 anti-condensation heater
2 IP22 enclosure protection
3 filter
We usually define the generator\'s ambient temperature to be at 40°C.
The ambient temperature should not be higher than 40°C, which is very important. If it does, the power of the generator should be decreased.
When ambient temperature is lower than 40°C, generator\'s power could be larger than rated power. When it is higher than 40°C, the power should be modified by following factors.
Temperature(40°C) Power factor
45 0.97
50 0.94
55 0.91
60 0.88
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| What size generator do you need? |
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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.
Below please find 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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Appliance |
Load (WATTS) |
Calculation |
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Air Conditioner 10000BTU |
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2000 running |
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5000 starting |
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Air Conditioner 20000BTU |
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3000 running |
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7500 starting |
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Air Conditioner 24000BTU |
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4500 running |
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11250 starting |
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Alarm System |
800 |
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Auto Washing Machine |
3000 |
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Borehole Pump |
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2000 Running |
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5000 Starting |
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Borehole Pump |
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750 Running |
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2000 Starting |
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Computer |
300 |
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Decoder |
200 |
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Deep Freeze |
400-600 |
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Dishwasher |
1450 - 2500 |
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Electric Fence |
600 |
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Electric Gate |
800 |
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Electric Heaters (per bar) |
1000 - 3000 |
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Electric Iron |
750-1000 |
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Fax/Answer Phone |
60-100 |
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Geyser (Standard 240l) |
3000 |
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Grill |
2000 |
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Hair Dryer |
2000 |
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Home UPS |
100-600 |
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Kettle |
850-2000 |
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Lighting - Domestic (per bulb) |
40-100 |
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Lighting - Outside Yard |
100-1000 |
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Microwave |
1000-3000 |
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Over (per element) |
2500 |
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Percolator |
500 |
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Plate Warmer |
400 |
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Printer |
60-1000 |
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Radio/ Stereo / Home Theatre |
200-500 |
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Refrigerator |
550-2500 |
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Sewing Machine |
80 |
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Stove (per plate) |
2000 |
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Swimming Pool Pump |
1500 |
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Television |
300 |
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Toaster |
750-1250 |
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Tumble Dryer |
2500 |
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Vacuum Cleaner |
250 |
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1000 Watts = 1 kW
1000 Watts = 1.2 KVA (for 3 phase only) |
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Sub Total |
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Total |
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The above calculation sheet is an indication of the common business and household rating of common appliances. This sheet should be used as an indication for the size of the generator that you require and should not be used in isolation. A load test or consultation with an Electrical professional is recommended.
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| What happens if you overload i.e. draw too much power from a generator? |
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| 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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| What can you run on a 5kva generator? |
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The following can all be run at the same time on a 5kva 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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| How do generators operate? (Step by step explanation) |
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| When the power goes off, first step would be to go to the distribtution 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 （manual transfer switch） and swtich 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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| How could you install a generator? |
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If necessary you need to ask a qualified electrician could help you install the generator . 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 noise do generators make? |
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| 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 extremely silent generators however some are quieter than others. |
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| Electric start or recoil start? |
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An able bodied male can easily "pull start" the 5 KVA and 6 KVA generators however females battle to start them so electric start is recommended for home use.
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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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It is best to have the generator connected to your main distribution 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.
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