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How to calculate circuit breaker and wire size?

By:Nader Updated:August 17,2020 16:23PM

1. How to calculate circuit breaker and wire size?

You just divide this number by the voltage at which it operates, which is 120 volts, 230 volts or 440 volts. Then, multiply this number by 125 percent. An easy way to do this is to divide it by 100 and then multiply it by 125. The rating of your circuit breaker must be larger than this total.

2. How do I know what size electrical wire to use?

Different sizes of electrical cable can carry different amounts of current. American Wire Gauge (AWG) is popular to measure cable. A larger AWG number indicates a smaller cable. Attempting to run too much current through too small of a cable can cause permanent damage to wiring. It can also start an electrical fire. Fortunately, there are a number of ways to identify the size of an electrical cable. These methods only require minimal equipment and are effective for virtually all cables.
One: Look at the insulation on the cable. Search for text written on the insulation. The last numbers in each string of text represent the AWG of the wire. If you cannot find any text on the wire, proceed to the next step.
Two: Cut the wire with your wire cutters. The cut should be perpendicular to the run of the wire.
Last: Measure the diameter of the cross-section in inches. The diameter is the distance from one side of the cross-section to the opposite side in a straight-line. Do not include the wire's insulation in the measurement.

3. How to install a circuit breaker

When we think it's difficult to install a circuit breaker, If you can follow the steps below and will find out how easy it is.
Step 1: Power down. Shut off your branch circuit breakers one at a time. Next, turn off the power to your breaker box by flipping the power main. Your power main should be a large switch above or below your breaker panel. 
Step 2: Remove the panel cover. Unscrew the panel cover to gain access to the breakers.
Step 3: Loosen the terminal screws. Turn the screws until the terminal and wires are loose. Pull the wires out of the breaker terminals.
Step 4: Remove the breaker. Press the breaker handle toward the outside of the breaker panel until it comes loose.
Step 5: Install your new breaker. Line up your new breaker with the clips on the side of the bus bar. Press the breaker down firmly until it snaps in place. 
Step 6: Reconnect the wires to the terminal screws and replace your panel cover.
Step 7: Power up. Turn on the branch circuit breakers and your power main.