HOW SAFE ARE YOUR CIRCUIT BREAKER AND WIRE CONDCUTOR FOR THE LIGHTING SYSTEM AT HOME?

Hello! Today, I am going to give information on how to know if the installed electrical circuit breaker and the conductor wires in the lighting system at home are theoretically correct and totally protecting us from any unwanted events. Such as, overloading, short circuit currents and electricity misused.
After this, the readers will be able to evaluate if the installed circuit breakers and the conductor wires at their homes were at standard or not? And they will be able to know the proper computation based on National Electrical CODE (NEC) and Philippine Electrical Code (PEC).

Let’s begin with the definition.

Circuit breaker

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Is an electrical device that is automatically operated electrical switch designed to protect an electrical circuit from damage caused by over current, typically resulting from an overload or short circuit.

Conductor wires

A pathway of electrical circuits.

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Misused and misconception of the usage of these device may cause damage in property, life and the like. So, with this simple tutorial everyone can gain simple knowledge about circuit breaker calculation and conductor wire calculation.

Example: A house with 12 - lighting outlets. Compute for the sizes of the following:

a. Size of the conductor wire.
b. Size of the circuit breaker.

Below are the procedures.

Procedure 1|

Compute the current for the whole lighting circuit of a certain house to know the size of the conductor wire to be used.

Now, to compute according to NEC/PEC, assume a 100W per lighting outlet.
Thus, (100 Watts / Outlets)(12 outlets) = 1, 200 Watts

To solve for the current use the formula below.

Formula :
P = VIcosθ
Where:
P – Power in Watts
V – Voltage (use 230 volts for Philippine power system)
cosθ – Power Factor (power factor is 1, because lightings are considered as resistive load)
Thus,
I = (1,200/230)
I = 5.22 Amperes

Then, use 2 – pcs. #14 AWG (2.0 mm2) THHN, THW or any equivalent conductor.

According to the NEC/PEC the current flowing on the wire should be only 80% of the total capacity of the wire or also known as ampacity. Thus, for #14 AWG (2.0 mm2) THHN, THW the ampacity is 15 A multiply it by 80%. So, for #14 AWG (2.0 mm2) THHN it should have only 12 A flowing on the conductor wire.

The 5.22 Amperes is much lower than 12 amperes. So, using #14 AWG (2.0 mm2) THHN, THW conductor wire is very safe.

Procedure 2|

Compute the size of the circuit breaker to be used.

According to the NEC/PEC the circuit breaker protecting a lighting circuit should always be in one circuit and protected with a breaker with a rating of 15 Amperes.