All of our electrical devices in the home require a consistent voltage to operate. The circuit breaker panel distributes the voltage from the power company safely throughout the home. A single circuit breaker, single pole, will deliver between 110 Volts Alternating Current (VAC) to 125 VAC. This is measured between the screw terminal on the breaker to the ground bar in the breaker box. A double circuit breaker, double pole, will deliver between 220 VAC to 250 VAC measured between the two screws on the breaker. Each screw terminal, on the double pole breaker, will deliver the same as a single pole if measured between the single screw terminal and the ground bar.
Things You'll Need
- Screwdriver, philips or slotted
- Volt ohmmeter
Shut off the main power breaker that supplies the circuit breaker box. This main breaker will be located at the top or bottom of the panel depending on the style of the circuit box. The switch will be identified as "Main" with an "on and off" label.
Remove the cover screws, using the screwdriver, that are holding the protective cover over the main bus bars of the circuit breaker box. There will be either four or six screws depending on the size of the panel.
Observe the layout of the main panel before restoring power to the box. There will be a ground bar to the left and or right of the circuit breakers. This ground bar should have both bare copper wires and white insulated wires terminated to the ground bar. There may be exposed places on the main bus bars. These bus bars are where the circuit breakers are plugged into and carry the voltage of the electrical system. Do not touch these bars, with your fingers or hands, when the panel is energized, you will get shocked.
Reenergize the main breaker. Switch the Volt Ohmmeter to volts. Place the black lead from the meter on the ground bar and the red lead from the meter to the terminal screw on the single pole breaker you want to check voltage. It should read between 110 to 125 VAC.
Place the two leads from the meter to a double pole breaker, one each to each screw terminal. The meter should read 220 to 250 VAC. Next check each screw terminal to the ground bar one at a time. Each voltage reading should be the same between the screw terminal and the ground bar, as in step four above. If not, the breaker may be bad and needs to be replaced.
Shut off the main breaker and replace the cover to the circuit breaker box. Once all the screws are in place and the cover is tightened, turn the power back on to normal operation.
Tips & Warnings
- Always remove the power to the main circuit breaker before performing any work on the circuit breaker box. Damage or serious injury may occur due to a short condition to ground, causing the bus bars to severely arc.
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