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All The Gen About Generators PDF Print E-mail
Monday, 04 June 2007

For all of you who have been affected by the recent blackouts and want all the gen about generators, I contacted Brian Bilton, Technical Advisor for the Electrical Contractors' Association (SA) KZN Region, who sent me the following useful information.

This article relates to a generator when used to supply a portion of, or the whole installation, when the main electricity supply fails, and it is connected to the existing main electrical distribution board in the premises.  It does not cover the free standing situation when a fridge or other appliance is plugged directly into the socket outlet on the generator.

A “genset” that energises a part of the installation that is normally alive when the main supply is in operation is potentially very dangerous and life threatening.
 
Why the need?

There has been a sudden increase in the number of queries the ECA (SA) is receiving about the use of generators in the home. It has already been involved in the investigation into a fatality arising from the use of a generator.  A genset, as they are often referred to, is either petrol or diesel driven, and is mechanically connected to an electrical generator

The engine needs to be started just as the engine in the car needs to be started. Some engines are started by the manual pulling of a rope attached to the engine similar to the type used to start the engine of a lawn mower.

Other more complex gensets have a battery with a starter motor and a switch or push button to start the engine, and the more advanced gensets are started automatically when the supply from the municipal supply authority or ESKOM fails. There are obvious advantages with this arrangement.

Most of the larger gensets are started this way and are be used in hospitals, and other critical applications.  However without this “nice to have feature” which comes at a price, the other means of starting the generator may present the same challenges that our favourite lawn mower presents. The tiresome task of pulling of a rope attached to the engine in the hope that the rope won’t break thus leaving you flat on your back; the spark plug is not sparking; or the wretched thing starts but is very erratic.  You are generating another form of power, the verbal variety. Remember now the pandemonium you are in. You are watching your favourite TV programme, supper is in the oven, the kids are busy with an assignment on the PC which, as usual, has been left to the last night before writing exams the following day.  You cannot see your way around to find a torch or a box of matches to assist you finding a candle, and it is probably cold and wet outside. You’re literally in the dark! Be very careful with matches near the fuel tank of the generator otherwise you will be faced with a very serious situation.

The generator part of the gensets will start generating power once the engine starts which will eventually stabilise at around 220 volts until a load or wattage is connected. This is where it is vitality important to decide what load is to be connected to the genset. In other words, what part or portions of the installation you would like to have on when the gensets is running. The greater the load the bigger the genset and the higher the cost.


The use of a generator in the home

Choosing a generator:

Before you choose a suitable generator for your home it is important to decide what you intend using the generator to supply. There are many types and sizes of generators so how does one select the correct one for your particular application? You will need to decide what equipment eg appliances or lights will be required to be operational during the time the generator is in operation. Again the more equipment to be used, the bigger the generator that is required, and the higher the cost. Never exceed the manufacturer’s specifications. Get the right advice before deciding which one suits your application.

Some guidelines to be considered when deciding which items of electrical equipment need to be retained when the generator is in operation:

Remember all the heating appliances will draw the most power - the stove, geyser, dishwasher, washing machine, tumble dryer, toaster, kettle, hairdryer etc.

Control the number of lights you use. Computers and electronic equipment consume little power, but be careful because these items can be very voltage sensitive.

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If the generator does not deliver a constant voltage and there are dips and spikes in the system, electronic equipment is likely to suffer damage. Most modern fridges are electronically controlled, and a fridge is likely to be high on the list of essential items. Depending on the time the generator is in operation it will be helpful to put into effect some of your internal load shedding.  Switch off some lights to allow you to boil a kettle etc.

The transfer or change over switch:

The connections between the municipal or Eskom supply and the generator supply are a vital part of the overall safety of the installation.  It is a requirement that the installer must ascertain the requirements of the supplier prior to connecting the genset.
 
The transfer or change over switch in a domestic installation, which is required when installing a genset, is likely to be a manual device which has three switching positions. These may vary depending on the switch, but most have a central off position and a position to the left and right of the off position. One is for the Main Supply and the other for the generator supply. This will mean that when the main supply fails the switch will have to be manually turned from main to the generator supply. The whole process will have to be repeated once the main supply returns.

These transfer switches can also be automatically controlled, but this system is far more complicated and costs a great deal more.

This “switching” procedure is a vital part of the process as a “back feed” is both potentially dangerous and can also damage the generator and all the electronic devices in the home - computers, TV, hi fi etc etc. The main supply and the generator supply must never run in parallel. The licensed electrician, who must carry out the installation, will understand the requirements for the wiring of these switches, as incorrect wiring of all the live, neutral and earth wires could be life threatening.

Installation and connection of a generator by qualified person:

Remember that this work must to be done by a registered electrical contractor who knows what he is doing. You can check whether your contractor is registered by contacting the local offices of the Electrical Contracting Board of South Africa, which are situated in each province in the country.  In addition always make sure that he issues you with a valid Electrical Certificate of Compliance.  NEVER attempt this work yourself. Remember that a Genset is in itself a Supply Authority and the dangers and risk of electrocution are exactly the same. 

Gensets and the law:

The South African National Standard (SANS 10142-1:2003) for the Wiring of Premises Clause 7:12 prescribes the minimum safety requirements for the installation of low-voltage generating sets. These are legal requirements, and failure to comply with these requirements could invalidate any home owners insurance should it be established that a fire or injury was caused as a result of the in correct connection to a genset.

The requirements contained in the Standard are of a very technical nature, and must be clearly understood and applied.

Carry out regular testing:

Gensets must be tested at regular intervals, and the tests must be carried out as if the gensets were in operation.

Other important considerations

The Position of the genset:


The battery
If the genset has an automatic start facility care needs to be taken of the battery. Just as a car battery needs care and maintenance.

Noise Factor
Gensets are noisy and therefore need to be positioned in a place where the noise will not intrude in the house or disturb your neighbours.

Heat Factor
Gensets will get hot so care needs to be taken that no one will get burnt by coming into contact with the hot exhaust pipe.

Exhaust Gas
The exhaust gas needs to be dissipated into the open air, and care needs to be taken that the gensets will not emit exhaust gas into a poorly ventilated room and thereby cause carbon monoxide poisoning.

Fuel storage
Unlike the toil of cutting the lawn with the petrol lawnmower and you can plan to make quick trip to the local petrol station to buy some fuel, no amount of sophistication of our genset will be of any use without fuel. Power outages occur when we least expect them.  Accordingly, fuel needs to be permanently available and stored in a suitable container, in a suitably ventilated room. Remember the petrol station may also be without power.

Information provided by the Electrical Contractors’ Association (South Africa) - (ECA (SA))

Brian Bilton (MIE)
Technical Advisor
Electrical Contractors’ Association (SA)
KZN Regional Office
031 312 6313
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