12.2. How to install electrical wiring: Circuit sizing

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Installing electrical wiring is a crucial step in building a home. It requires careful planning and meticulous execution to ensure the home is safe and energy efficient. In this chapter, we will discuss circuit sizing, a key aspect of electrical wiring installation.

First, it is important to understand what an electrical circuit is. An electrical circuit is a closed path through which electricity flows. It is made up of a conductor, like a wire, that connects a power source to one or more electrical devices. Sizing circuits correctly is crucial to ensure they can handle the amount of current that will be required of them.

Sizing a circuit involves determining the proper wire and breaker size for the circuit. Wire size is determined by the amount of current the circuit must handle, while breaker size is determined by the maximum amount of current the circuit can safely handle.

To determine the proper wire size for a circuit, you need to know the amount of current the circuit will carry. This is usually determined by the power of the devices that will be connected to the circuit. For example, if you have a circuit that will power a 100-watt light bulb and a 200-watt fan, the circuit will need to handle a current of approximately 2.5 amps (300 watts divided by 120 volts).

Once you know how much current the circuit needs to handle, you can use a wire sizing chart to determine the proper wire size for the circuit. For example, a 14 AWG wire can handle up to 15 amps of current, while a 12 AWG wire can handle up to 20 amps.

The breaker size for a circuit is determined by the maximum amount of current the circuit can safely handle. The circuit breaker serves as overload protection, shutting down the circuit if the current exceeds the safe limit. The size of the circuit breaker must be chosen so that it switches off the circuit before the current can cause damage to the wire. Typically, the breaker size is 125% of the maximum current the wire can handle.

For example, if you have a 14 AWG wire that can handle up to 15 amps of current, you should use a 20 amp breaker (15 amps x 1.25) for that circuit. This ensures the breaker will trip the circuit before the current can damage the wire.

In conclusion, proper circuit sizing is an essential part of electrical wiring installation. It ensures that the circuits can handle the amount of current that will be required of them, and that they have adequate overload protection. When planning the electrical wiring for your home, it is important to consider circuit sizing to ensure a safe and efficient installation.

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4512.3. How to install electrical wiring: Choice of materials and equipment