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Why do some ECMs have 16-pin connectors while others have 4-pin connectors?
In the direct drive applications of HVACR, we see three different designs of electronically commutated motors, or ECMs. Constant speed ECMs are used with axial fan applications, such as condenser fans. Constant torque motors are typically used in blower applications that are in the lower efficiency equipment. Constant airflow ECMs are used in blowers on the highest efficiency equipment. We’re going to concentrate on the blower motors, and more specifically, the constant airflow, in this Tech Tip.
The constant airflow motors utilize pin terminals in the connectors, while the constant torque use spade terminals. The constant torque motors have four spade terminals on the communication side of the connector, while the constant airflow could have 4 or 16 pins on the communication side of the connector. This communication is between the equipment circuit board and the motor controller. The 5-pin side of the connector is for the power supply in energizing the motor.
Historically, the most prominent constant airflow motors have been those produced by Regal Beloit and their associated companies. These include models 2.0, 2.3, Eon, 2.5, and 3.0. With constant airflow, the system is programmed with information regarding airflow, delays, and other features, resulting in optimized performance and control of the system. The difference between the 16-pin and 4-pin motors is where this information is stored and how it is communicated between the equipment circuit board and motor.
The 2.0, 2.3, and Eon models all have 16-pin connectors. The programmed performance information is stored in the controller of the motor. Communication between the equipment circuit board and motor is with AC/DC voltage or Pulse Width Modulation (PWM).
The 2.5 is also a 16-pin motor. However, the programmed performance features are stored on the equipment rather than on the motor controller. In addition, communication between the equipment and the motor is with serial communication rather than with PWM. This communication is with binary code, similar to that used with computers. Only one of the 16 pins is required for this communication.
The 3.0 motor is a 4-pin motor. Just like the 2.5, the programmed performance information is stored on the equipment and not in the motor controller. Communication between the equipment and the motor controller is also serial communication using binary code.
Understanding the differences in ECMs is critical when it is necessary to service the equipment. Knowing their characteristics makes it easier to understand how they work and what it takes to replace one that has failed.
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