One of the most important components of an HVAC system is the fan motor, which circulates the air through the system. Fan motors can be classified into different types, such as single-speed, multi-speed, variable-speed, and electronically commutated (EC) motors. Each type has its own advantages and disadvantages, depending on the application and the design of the system.
In this article, we will focus on one specific type of fan motor: the 5 wire motor. This is a type of EC motor, also known as “brushless DC” motor, that has a built-in microprocessor controller that allows the user to control the motor speed. It is more energy efficient than single-speed general purpose AC motors and can replace shaded pole and permanent split capacitor motors used in HVAC systems.
How does a 5 wire motor work?
A 5 wire motor is a bipolar design with four coil windings sharing a common 12V power feed. The four wires are black, orange, brown, and yellow, and they correspond to the four coils. The fifth wire is white, and it is the neutral wire. The motor also has a capacitor, which is a round device that stores electrical charge and helps the motor start and run.
The motor operates by sequentially changing the magnetic fields that surround the inner drive rotor. The rotor has permanent magnets with alternating fields embedded along its axis. To create movement, the HVAC control module grounds each of the four coils in a predetermined sequence. It is this sequence of magnetic fields that cause the rotor to move in either direction in stepped increments.
The position of the rotor is determined by the HVAC control module by counting pulses from the non-energized coils as the permanent magnets pass those coils. The HVAC control module can drive the applicable coil to reach the exactly desired position of the rotor. The motor does not have physical stops; the physical stops are provided by the door within the housing. These stops are learned by the HVAC control module during calibration.
How to wire a 5 wire motor?
The wiring diagram for a 5 wire motor depends on the type of HVAC system and the original motor that is being replaced. The original motor may have 3, 4, or 5 wires, and each wire may have a different color and function. Therefore, it is important to check the wiring diagram of the original motor and the HVAC system before attempting to wire the new motor.
Here are some general steps to wire a 5 wire motor:
- Disconnect the power supply and the capacitor from the original motor.
- Remove the original motor from the fan assembly and note the position of the wires and the terminals.
- Compare the wiring diagram of the original motor and the new motor and identify the corresponding wires and functions. For example, the black wire of the new motor is usually the high speed wire, while the red wire of the original motor may be the low speed wire. The brown and yellow wires of the new motor are usually connected together and do not have a corresponding wire in the original motor.
- Connect the white wire of the new motor to the neutral wire of the power supply, which is usually white or gray.
- Connect the black wire of the new motor to the hot wire of the power supply, which is usually black or red.
- Connect the orange and purple wires of the new motor to the opposite terminals of the capacitor. The capacitor may have markings such as “C”, “FAN”, or “HERM” to indicate the terminals. If not, use a multimeter to measure the capacitance of each terminal and connect the orange wire to the terminal with the higher capacitance and the purple wire to the terminal with the lower capacitance.
- Connect the brown and yellow wires of the new motor together using a wire nut or a crimp connector.
- Secure the new motor to the fan assembly and restore the power supply and the capacitor.
- Test the operation of the new motor and verify the rotation direction. If the rotation is incorrect, reverse the orange and purple wires on the capacitor.
How much does a 5 wire motor cost?
The price of a 5 wire motor may vary depending on the brand, model, size, and specifications of the motor. According to Grainger, a leading supplier of industrial products, the average price range of a 5 wire motor is between $100 and $300. However, this does not include the cost of installation, which may require additional tools, materials, and labor. Therefore, it is advisable to consult a professional HVAC technician before purchasing and installing a 5 wire motor.
