BUYING A GENERATOR
kVA TO AMPS
kVA to kW
A generator is an expensive investment, and also expensive to maintain and to operate. Here is some advice
you can use to ensure that you get the right generator for your needs.
Do not just GOOGLE “generators” and then click on the first name you see and buy a generator. Your buying
an expensive asset, which if maintained correctly, should last you many years.
YOU ARE GOING TO BE SPENDING A LOT OF MONEY SO TAKE A BIT OF TIME AND EFFORT AND
SPEND IT WISELY.
Sizing your generator is critical, too small and you will damage it and may even damage equipment
connected to it. Too big and you are wasting money. Ideally a generator should run at between 70 and 80% of
capacity, though this is not always achievable especially when you have motors, refrigeration, air conditioners
or geysers connected to your generator.
So how do you select the right generator?
STEP ONE: Why do you want the generator?
Do you want it to avoid the inconvenience of being with out power at home, or to ensure your business can
keep doing business.
If for home use consider the following:
Load-shedding lasts between 2 and 3h on average sometimes twice a day,
You fridge can will hold its contents cold during these periods,
A Luke warm shower never killed anyone,
Generators need a lot of space and fresh air to operate properly,
Generators produce carbon monoxide which is deadly,
The larger the generator the more costly it is to buy, install and maintain, try keep it as small as possible
Go through your home and decide what you really need and what you can live without for a few hours.
Here are a few tips that can help reduce the size of the generator you need:
Have your geyser connected to a solar panel.
Invest in a Weber gas braai, for cooking your meals during load-shedding, the added benefit is that,
WITH THE CORRECT FITTINGS, it can also be used to light your home.
If it is for business use, then besides looking at the list above consider the following
Lighting can you get away with reducing the amount of lights you use when there is load-shedding
Getting small (850 Watt etc) UPS’s for your computors
What items are critical to ensure you can conduct your business and what items are purely there to make
All these can contribute largely to lowering the size generator you need, thus saving you money whilst still
meeting your objectives.
STEP TWO: Getting the right information from the right people.
Now that you have an idea of what you want it is time to bring in the professionals to help you make the final choice.
Do not be afraid to ask them questions, or to get more than one to come in to advise you. They will help you with the
Determining your current needs this can be a lengthy process depending on the size of the building, the number
of DBs you have etc. But for a house it is much simpler.
Is it better to buy a generator to supply everything, or to split your DB into two parts for essential and non
essential power. Having certain items run only in Mains supply can mean doing a lot of extra electrical work due
to having to run new wires etc. So it could be that these changes will actually cost more than getting a larger
Items like your UPS, air conditioners, motors etc need to be carefully looked at, because these items have a
start up current that is many times higher than what they use when running, so things like delay timers and other
electrical modifications can be looked at to reduce the size of the generator your need. ONCE AGAIN COSTS
OF CHANGES VS SAVING IN GENERATOR SIZE must be looked at and explained to you.
Once all of this is done you can determine the size of the generator you need.
Next choice is the fuel source of the generator, do you want petrol, diesel or Gas. Each has its pros and cons but
generally the best choice is diesel. These days you get get diesel sets that supply a little as 2Kva of power.
Now that you have chosen what set you want you need to decide where to put it, there are many legal and
safety requirements you need to consider such as:
a) The generator must be at least 1M from all boundary lines,
b) The exhaust outlet must take the dirty air out of the building and must be at least 1M above the structure, so
even if it is an enclosed set in the middle of a field the exhaust must be 1M above the enclosure.
c) The generator must have a bundwall that can contain 110% of ALL the fluids in the set.
d) Generator’s require fresh air both for cooling and for combustion, you will be surprised how much air they
need so it is important to know this when deciding where to place the set.
e) The cables must be run according the the SANS
The person consulting you must be versed in these laws and able to assist you in ensuring your installation is
f) Generators create heat and carbon monoxide (these two points can never be stressed enough) make sure
they have a way of getting these out the building.
g) An often over looked item for generator installations are the need for servicing and refuelling of the generator,
ensure you know what side the refuelling point is and that there is room for the technician to access all the filters
and oil outlet for servicing of the set.
Other things to consider are:
a) Do you want the change over panel to be part of your DB, in a separate Box next to your DB or on the
generator. Remember that if the panel is on the generator you will need to use more cable for the installation.
b) SANS requires that ALL BD boards fed from generator meet the following requirements:
I) The BD must have signage indicating that it is fed by a generator
II) The DBs must have lights to indicate whether the DB is being fed via Mains or a generator
III) All DBs must have emergency stops that allow for the immediate stopping of the generator in case of an
Depending on the size of the generator (an the area you live) you could require extra permits for the installation
IE. in Cape Town you will require a fire permit if your fuel tank is over 200L etc
The last choice is whether you want this to be a manual or automatic starting system, this is totally up to you.
SAFETY AND LEGAL NOTES:
1)NO CHANGES MAY BE DONE TO A BUILDING’S WIRING UNLESS DONE BY A PROFESSIONAL PERSON
CERTIFIED TO DO THE WORK.
ALL CHANGES DONE TO YOUR BUILDING’S WIRING REQUIRE THAT A NEW COC BE ISSUED
ANY INSTALLATION THAT FEEDS POWER INTO YOUR DB MUST BE A PERMANENT INSTALLATION
GENERATORS CREATE CARBON MONOXIDE
THE GENERATOR AND THE MAINS MUST BE SEPARATED INCLUDING THE NEUTRAL, THIS
SEPARATION MUST BE BOTH MECHANICALLY AND ELECTRONICALLY INTERLOCKED.
MANY GENERATORS HAVE NOISE LEVELS ABOVE THE LEGAL LIMIT FOR RESIDENTIAL ARREARS.
MOST SMALLER (UNDER 15Kva) GENERATORS RUN ON V-V-O SYSTEM.
MEANING THEY HAVE 115VON THE LIVE (if measured to earth) AND 115V ON THE NEUTRAL (if measured
to earth) THESE ILLEGAL FOR USE IN A BUILDING.
How do these effect you?
Only certified electricians are allowed to touch your building’s wiring, if your building is three phase then
only a master electrician may do the work, as only they are certified to issue the COCs.
If you building’s COC in not up to date your insurance company can cancel your insurance, and if anyone
gets hurt you can be held legally liable.
Many home installations use a plug and lead to feed power to the building. In some cases the person simply
plugs the generator into a wall socket to feed the house. In others there is a lead going to a manual or even auto
switch to supply power to the DB. ALL OF THESE ARE ILLEGAL. The generator must be hard wired to a
dedicated breaker which in turn is hard wired to the change over switch, be it either manual or automatic.
Ensure that your generator’s exhaust fumes are removed from the building, in accordance with the
environmental act the exhaust must extend 1 meter above the roof.
The change over between mains and generator supply must be done with a proper change over system
that will ensure that there can be no feed back onto the mains when your generator is running.
Noise pollution laws vary from area to area so ensure that you know what the limits are in your area, especially
if you live in a complex. There are many options that can be taken to reduce the noise levels to ensure
Ensure that your generator is of the V-O-O type, most V-O-V sets can be converted safely. If your electrician
or the generator supplier is not sure what your talking about DO NOT USE THEM GET SOME ONE ELSE.
Copyright © NVS Krag 2018