Electrical safety is critical. Electricity kills and it can cause fires. Always ensure that work is done by licensed electricians and that all wiring and fittings comply with best practices and local codes.
Electrical wiring in your new home
Power feeds to the house from the local power supply. The electrical current flows through wires, a bit like water through a pipe. Thinner wire restricts the flow of electricity (much the same as a small hose pipe). There’s more friction. Friction causes heat which can lead to fires. It also causes losses so the power you get out at the end of a thin wire is less than that which enters it. This means that the longer the wire the more losses will occur. But thicker wires are more expensive. The size of the wire is measured in gauges or square millimetres. Larger gauge numbers indicate smaller diameter wires.
Electrical wires are normally copper. Sometimes aluminium wiring is used but this is less efficient than copper so needs to be larger diameter for the same equivalent power. The wire is insulated, usually in plastic, to prevent it from transferring the current elsewhere which may happen when it comes into contact with water, metal surfaces or even a person. Wires are often rated according to whether they can be installed in wet areas or dry, and also according to the heat they can withstand. So wires installed in a roof may have to withstand higher temperatures.
All electrical cables have a live wire, neutral and the earth or ground wire. These have different colours which are mandatory in your country. The different wires should never be mixed up or connected incorrectly.
Every item that consumes electricity has a power rating. The power (or watts) is calculated by multiplying the current (measured in Amps or A) by the voltage (V). Power is delivered to your house at a set voltage which is the same throughout your country, normally 120, 200, 220 or 240 Volts. So if you have a heater that’s rated at 1kW which is 1000 Watts and your supply is 200V then you require 5A of current. An item that requires 5000W with a 200V supply requires 25A.
The oven in our house needed to be replaced. When we looked for a replacement all ovens that fitted the space of the old oven required 5500 watts of power. Since we had 240V we required 23Amps, but the circuit breaker was only rated 16A. Investigating further we discovered that the wires supplying current to the oven could not take a bigger current. Installing a smaller oven meant there would be a gap below the oven in the kitchen which required patching. But a smaller oven would also be totally inadequate for the house which is a family home of four bedrooms. Obviously when the wiring was done for the house they gave little thought to installing an adequate supply to the oven. At large expense we had to install a new circuit breaker and new wires to the oven. Installing a larger circuit breaker only would have resulted in too much current going through the wires to the oven, causing them to burn out, possibly even causing a fire.
Single Phase or Three Phase Power
The power connection from the utility provider could be single phase or three phase power. Single phase connections are usually cheaper and the monthly fees to the provider are less than for three phase power. But some products such as swimming pool motors, larger air-conditioners and even spas require three phase power. In addition three phase power provides more power than single phase. So before deciding whether you want a single phase or three phase connection you should decide what electrical appliances you will install in your house, know what their power requirements are and calculate what the total requirements for the house will be.
In the next article Electrics for your new home build part 2 we will discuss this topic further.
Following articles will look at what you should no about lights Choosing lights for your new home and planning the location of electrical sockets or plugs Electrical outlets in your new home.
This is an extract from the author's book 'An Introduction to Building and Renovating Houses: Volume 1 Hiring Contractors, Managing Construction and Finishing Your Home'.
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