By Charles Nicolson
Even though it is a perfect evening at just after six o`clock under a deep blue autumn sky in Johannesburg I catch myself, once again, murmuring an audible “Thank You” as the lights come on.
Not that I need any lights just yet, but it is reassuring to hear the soft hum of the refrigerator ensuring that frozen food as well as other cooled liquids such as milk will not require earlierthan-usual replacement. However, I wonder who am I actually saying “Thank you” to?
Figure 1 A typical portable 750kW 220230 VAC generator
The person or people who moved the switches or pressed the buttons so that electric power was restored to Block 2A and, at the same time, removed power from another block in which reactions from residents and others in the affected area would no doubt be expressed more abruptly and in words far different than my murmured “Thank You”? Or is disconnecting electrical supply to an area and subsequently reconnecting several hours later now actuated by pre-programmed computerised control systems? Probably not, I thought, bearing in mind that even small electrical grids fed from sub-stations contained various ranges of voltages, amperages and other complexities requiring control as well as safety considerations.
Time for tea.
A welcome return to normality; but as I switch the kettle on the power dies again. Hoping optimistically that some error in the procedure for restoring the power had occurred and that it would be rectified soon and remain on at least until the next scheduled ‘load shedding’ arrived, I left everything ready for brewing up the tea, including a check that the kettle was not switched on. Why bother to check if a standard 2000W domestic kettle is switched off? 2kW is a tiny, virtually negligible part of the multi-megawatt demands of power by the total of over 50 suburbs in Block 2A, even during the early pre-morning period of lowest power demand.
The reason is partly habit because electricity usage on the property where I live has far outgrown the design capacity of the original installation put in about 70 years ago. For example, the original 2kW hot water geyser has been supplemented by two more 3kW units and there are now three refrigerators so too many additional appliances coming on simultaneously causes trip-outs on the incoming supply panel which is awkward to get to for re-setting the trips. The other part of the reason is a practically insignificant but personal recognition of the efforts by the many people involved in both Eskom and City Power who are genuinely striving to improve both quantity and quality of electrical power supplies.
A couple of years ago I was asked by an old friend, who also lives alone in a small rented garden cottage of similar size in a neighbouring suburb, to calculate the minimum-sized generator he would need, so that during load shedding durations of four to five hours he would be able to use two ordinary electrical lights, a 3kW electrical fan heater, a 900 watt electrical /microwave oven, his 2kW kettle and his television set with decoder for DSTV. This total capacity of about 6.5kW would need a generator rated at around 9kW so that it could cope with the appliances being switched on in sequence and then operate at a baseload of around 70% without producing too much clattering noise. In addition, if he wanted the generator connected permanently into the existing 230V wiring system the installation would have to be professionally done and recorded which would cost an additional amount of somewhere between R10 and R15 000.
However, the alternative of a simple six-plug bar adaptor with a suitably sized built-in trip switch installed on an inside wall would require installation only of a few metres of exterior supply cable and normal 230V interior connection plugs and cables to the appliances and the TV so that they could be connected or disconnected, and switched on and off as required. This was what he decided on and when I saw the completed installation, I was suitably impressed – and envious. There was no getting away from the noise of the generator, even though it was located in a rain-protected open garden shed several meters away, but the disappearance of virtually all the irritations brought on by load shedding almost completely overshadowed this small inconvenience. I found myself slipping into convenient thinking wondering what the resale value of a generator would be; remembering the times when power had been off during most of a night and all of the following day; luckily I had kept just enough old newspapers to mop up all the condensate from the fridge and freezer; now – where was that pack of candles I bought a few weeks ago?
When power subsided for the second time, it remained off for almost six hours. Less than halfway through this powerless period my laptop battery failed. The following morning, I went to the local computer shop, owned and staffed by very knowledgeable and friendly people. After only about 15 minutes I left with not only a new computer battery but also another battery similar to, although a bit larger than the batteries which operate driveway gates and garage doors. Packed into a neat compact box around the battery were electrical and electronic components making up an assembly which automatically provided charging for the battery as well as a 450 watt, 230VAC output.
Enough for a couple of lights, TV, charging a cell phone and even back-up for a computer if necessary. At a price of R4 780 inclusive of VAT this new ‘appliance’ has so far delivered exactly what it was designed to do – lighten the burden of load shedding even if only for three hours or so. No heating or cooking but simple gas cylinders and burners are better and more convenient for those functions.
This commentary has been simply a personal experience in a single residential dwelling referring to only a few domestic and other appliances and electrically powered items. Obviously, industrial, commercial, agricultural and many other organised activities consume far larger amounts of electrical energy, often within much smaller areas. We are told that Eskom still needs a year or more to develop and consolidate into a settled situation in which switching off supplies to designated areas becomes a genuinely seldom-used option. However, there seems to be a general feeling of transition from negative to positive which sounds encouraging and appropriate for the future electrical situation of South Africa.
Shown below are examples of recommendations by Eskom on electrical power requirements for various domestic installations and appliances.
POWER CONSUMPTION CHART
This chart is an example as to how wattage varies between various electrical devices. It is not meant to be a strict guide to calculate actual requirements. For the most accurate calculations, refer to the owner’s manual of each device, tool or appliance, or consult a professional electrician:
