LETTER: My useful load-shedding tips – resident
Resident explains why you should switch off all your household appliances when the power goes out, and what to do when it comes back on again.
• David Bradley writes:
When you start your car, the DC motor starter engages with the engine and pulls 150 amps from the battery. As the engine picks up speed, this current drops to about 30 amps. Initially it runs at five times full motor power, but if you use the starter many times or for a long time, it will flatten the battery and overheat the starter motor and cables.
In your house you have several AC motors – deep freezer, refrigerator, gate motor, pool pump etc.
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These motors pull seven times full power at start-up so when load-shedding ends and the power comes back on every appliance in your area starts up at the same time. The load on the system is seven times the normal full load, and the system cannot cope with it so we get cables melting, contractors burning out and more downtime.
The geyser is not a major problem, it pulls 10 to 12 amps at full load and does not go over this so when power is restored there is no surge from it, but several hundred geysers all coming on at the same time will put strain on the system.
If you want to eliminate power surges, low mains voltage at start-up, protect your equipment and stabilise the system quickly.
When the power goes off switch off all your household appliances and when the power comes back on give it a few minutes for the load to stabilise, then you can switch them back on one at a time.
