How to Wire a Three Phase Circuit Breaker

In commercial and industrial applications, the use of three-phase power is common. This type of power is necessary for large motors, welding equipment and other large loads. The breakers are usually much larger than residential breakers. Three-phase power has three hot wires instead of one. There is no neutral wire to attach in this type of panel. Grounding is the same as for any other panel.

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Wiring a three-phase circuit breaker is simple.

Step 1

Turn off all power to the breaker panel. This is usually a main breaker or a transformer.

Step 2

Open the panel cover(s) and remove the breaker front from the panel. There are usually several screws holding it onto the panel. Use a screwdriver to remove the screws.

Step 3

Check all the main terminals carefully, using a voltmeter, to ensure that the power is off. Measure the voltage between each of the hot wires and then check each terminal to ground.

Step 4

Locate the three hot wires entering the panel. Using a screwdriver, loosen the terminals on the breaker. Place one of the wires under each lug on the breaker and tighten until snug.

Step 5

Locate the ground entering the panel, place it under a ground bar lug, and tighten until snug.

Step 6

Install the panel cover(s) and screws. Carefully replace the cover(s) to avoid damage to any wires.

Step 7

Turn on the power source. Check the operation of the device.