How to Wire the Red, White, and Black Wires In a 115-Volt AC Motor

Electric motors have a variety of uses and configurations for those uses. Some of these configurations require the use of multiple-speed 115-volt motors. Multiple-speed motors are typically used in fans, like those in HVAC equipment, whole-house fans, swamp coolers, and anything else that may have that need. Using the right wires will obtain function or comfort for your application.

Reading the label plate will give the exact wiring configuration based on your specific 115-volt motor. Typical wiring calls for a black wire for high speed, a red wire for low speed, and the white wire will be the neutral. One important consideration is that of proper grounding. All electrical wiring needs to have a good ground for the safety of your family and your home.

Multiple speeds make the motor more useful for many applications. For instance, in a warm air furnace being used in a central air conditioning system, the two speeds will be used for both heating and cooling. This utilizes both speeds independently as necessary for the appropriate season.

While the furnace is moving air for cooling purposes in the summer, the motor will need to run at high speed for best operation of the cooling system. This will require the black wire to be integrated into the cooling control circuit of the furnace. During the heating season, the red wire will operate the motor in the furnace at a lower speed and still sufficiently heat the home. This is a general guideline, and reading the label on your specific motor will provide more detail.

If you are only in need of one speed, such as on a whole-house fan or a swamp cooler, you may find that the fan is not moving as much air as you would like. This may be because the fan is wired at a lower speed, and a speed selector switch is not installed. After shutting off the power at the breaker, take the red wire that is connected to the power supply and swap it for the black wire. This will increase the speed of the motor and provide better airflow across the fan.

Basic 115-volt electrical wiring requires that the electricity makes a completed flow of energy. That energy, in this case AC power, alternates back and forth between the power wire (black or red) and the white wire known as the neutral. Without the completion of that flow of energy, nothing will happen. The speed of the motor is determined by the internal wiring inside the motor, known as windings, and these windings complete the circuit. They are what turn electromagnetic energy into a useful mechanical energy. In the case of a two-speed motor, there will be two sets of windings which in turn give two different speeds based on the number of iron ore poles inside the motor the windings are wrapped around.

Whatever your need to wire a red, white, and black 115-volt AC motor, the understanding that the black is for high speed, the red is for low speed, and the white is neutral is the simple basis of the situation. Whether terminating to a speed selector switch or manually changing wire speeds, shutting off the power at the breaker before performing any electrical work is the safest line of defense against injury.