Given the local electrical load shedding that we are currently experiencing, the focus of this edition is based on the guidance as to the required size and type of the standby electrical unit, as well as the associated essential safety requirements.
There are three main standby electrical generating systems currently available of the market.
These are:
Standby generator,
Electrical inverter and
Solar panels
The electrical capacity of each unit is rated in either kVA or kW.
Generators are available in a variety of sizes and operate on either petrol or diesel. They are available in either manual or automatic start.
These require adequate external storage space for both the generator, fuel storage and suitable ventilation to accommodate the exhaust fumes.
In the case of the larger units, it is essential to incorporate a battery charger to ensure that the battery is adequately charged when the system is to be started.
Electrical inverter is similar to a UPS as used for the energy back-up on computers – the only difference being that the inverter has a considerably larger electrical capacity than that of the standard computer UPS.
The electrical capacity of the inverter is limited to below 10 kVA.
Like the UPS, the inverter is silent and can “take up the electrical load” instantaneously.
One major advantage of the inverter over the generator is that the device is noise-free; there is no storage requirement for fuel and above all, there are no exhaust fumes.
Solar panels are governed by the size of the panel and are reliant on the available sunshine.
Accordingly, their output power is limited in capacity and output voltage of 12 volts.
Step 1
Given the limited capacity of all standby systems, it is essential that one does their homework to determine the magnitude of the power required to support the required electrical load.
After determining the list of essential electrical items, it is necessary to document the kVA or kW capacity of each item and to calculate the total load required.
Typical essential electrical loads are:-
a Access and security control devices,
b Fridge and kettle,
c Cooking appliances (if applicable),
d Light circuits and
e Geyser
Step 2
Once you have ascertained the required load capacity, the next step is to choose the type of standby power system that is most suitable to your needs.
Step 3
In the case where the size of standby system has a lower capacity rating than that supplied by the existing main distribution board:-
a Provision must be made to segregate the selected circuits within the distribution board.
b A manual change-over switch is to be installed to enable the electrical supply to the main distribution board to be sourced from either the main incoming supply or the stand-by supply unit.
c A mains supply recovery alarm buzzer or flashing light is to be installed to notify the consumer once the main electrical supply has been restored.
Note
In the case of a manually operated generator, it is essential that, upon starting the generator, it must attain full speed before the selector switch (referred to in step 3b above) is switched from “Mains” to “Standby” position.
I strongly recommend that after the installation of a stand-by electrical system, the system be activated at least once a month to ensure that the end user is comfortable with the “new device” and also to ensure that there are no disappointments when a load shedding interval occurs.
In conclusion, please feel free to contact me for any advice or queries relating to the electrical installation.
Also, having spent ten years lecturing in electrical engineering, I am available to give talks to interested groups.
My email address is anthony.murdoch7@gmail.com.
Here’s to your electrical safety.
