Variable Speed ECM Blower Motors

An ECM Variable Speed Blower Motor in a squirrel cage blower

Variable Speed ECM Blower Motors - Variable speed ECM blower motors have become increasingly popular in residential air conditioning and heating systems. From an engineering perspective, these motors increase the efficiency of the systems and offer a whole range of other benefits that help the system and the consumer. Furthermore, comfort is enhanced using ECM blower motors along with noise reduction.

Variable Speed ECM Blower Motors

Variable Speed Blower Motors first offer a higher efficiency for air conditioning systems based on the manufacturer’s set up of the control with the ECM Variable Speed Motor. Each manufacturer calls it a different thing such as Trane calling it the Comfort R and Carrier calling it Infinity Control.

Despite what the manufacturer calls it helps efficiency with air conditioning by starting the blower slowly and letting it run at a 50% speed for the first few minutes (up to 7 minutes) to remove more humidity. That increases comfort and efficiency by removing more moisture from the air.

Consequently, the lower the humidity in the cooler, you will feel so the variable-speed blower with this type of control will enhance comfort.

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Variable Speed ECM Blower Motors | Manufacturers and Benefits

ECM variable-speed motor manufacturers include General Electric and Emerson. Emerson offers it’s very own packaged control and control program to meet various control sequences to achieve efficiency and comfort for any manufacturer that uses the Emerson variable speed ECM blower motors for their equipment.

Other benefits include:

  • Soft start capabilities which will reduce the high inrush current like conventional blower motors.
  • Precision control to deliver a set amount of CFM’s for whatever the HVAC equipment manufacturers need for their equipment for airflow control.
  • High efficiency reduces energy bills.
  • Very quiet operation
  • Better comfort as described above

One of the disadvantages includes a high replacement cost if something happens to the motor or controls. Furthermore, ECM variable-speed motors need the attention of a qualified HVAC technician if something goes wrong as special diagnostic tools are required to diagnose any problems which may arise with the motor or controls.

Utilization and High Efficiency | Variable Speed ECM Blower Motors

These motors are typically offered in the medium to higher-end models of air handlers and furnaces, so you will have to pay a little more for the initial cost. Still, the benefits will give you a payback in the future with increased comfort and higher efficiency. Additionally, here at High Performance HVAC, we always recommend going for higher efficiency models.

Furthermore, because the cost of energy is not going to go down in the future and the high-efficiency models will help reduce the cost of energy so your utility bills will be reasonable in the future. Furthermore, the bonus this air handler or furnace component is it also adds comfort while increasing efficiency.

Troubleshooting Basics

Never assume the blower motor is bad. Always perform a cursory look at other components and inputs before condemning the ECM blower motor. Additionally, check the air filters and ductwork integrity before beginning component checks outlined below. Furthermore, the system needs the proper airflow to function correctly.

Troubleshooting Steps | Variable Speed ECM Blower Motors
    1. Check the main control board in the air handler. Wiring connections, including the thermostat wire coming from the thermostat. Always perform these checks with the power turned off. Check for loose connections, corrosion, and burned spots on the board. Some HVAC equipment has an additional control board for control of the ECM blower motor in the air handler. Also, check all the connections going to the motor, including pins inside the Molex plug connection. Additionally, a bent or loose pin will cause problems. Finally, a plastic Molex plug should make the connection between the motor and the control board.
    2. Next, check the input voltage on the board. Restore power and use a voltmeter to check both the primary line voltage and the control voltage. Additionally, the control board should use 24 volts for the control voltage, and all voltage ranges should be plus or minus 10%. Make sure that the safety circuit is suitable. Moreover, switches in the safety circuit will keep the system from running.
    3. Using the manufacturer’s instructions, check additional settings on the control board. Many have dip switches that will control RPM’s for the proper airflow for the sizing requirements of the system. Ensure these are correctly set.
    4. Ensure when you start the system that you wait for the program delays. Moreover, an ECM blower motor, adequately programmed, will start very slow. Then it will ramp up to low speed according to what the program calls for the settings. Finally, after a specific period, usually around 7 minutes, the blower will ramp up to 100% of the program according to where the dip switch settings are set for RPM’s or CFM’s.

Variable-Speed ECM Dip Switch Settings


Variable Speed ECM Blower Motors

Furthermore, if this doesn’t work then and you still have problems check with the manufacturer for an ECM blower motor troubleshooting flow chart or guide. Additionally, some manufacturers have a diagnostic tool that will confirm specific problems. The diagnostic tool can indicate if the motor or the controls are bad. Finally, if the motor is turning too many RPM’s or not enough RPM’s and is causing issues with the air conditioning or heating system because of improper airflow then it is a good idea to check the dip switch settings on the board. Good luck.

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Variable Speed ECM Blower Motors