Replace a PSC direct drive blower motor

If you’re in need of a PSC direct drive blower motor or just looking for a simple guide on how to replace one, cfm has you covered! We’ll be using the Evergreen motor in this example, so the same process won’t apply for a belt drive blower. We broke the process down into three segments, with a handful of sub segments to keep it simple


Suitable Applications:

The Evergreen motor is designed as a replacement motor for use on the following types of HVAC systems.

  • PSC Direct Drive Blower Motors only (Not for use on Belt Drive Blowers)
    • 115 or 230 VAC
    • 1/5 HP thru 1 HP
    • Residential and Light Commercial
      • Split Systems and Packaged Units
    • Clock-wise (CW) or Counter Clock-wise (CCW) rotation

Before Installation:

  1. Make note of the current motor speed selections.
  2. If the Existing blower motor is operational –
    1. Record the Total External Static Pressure (TESP)
    2. Record the Temperature Difference across the unit in Heat Mode and/or Cool Mode

Installation of the Motor:

Motor Bracket and Mounting:

  • The Evergreen motor requires a belly band style mounting bracket.
  • The Evergreen motor is a NEMA 48 frame.
    • This is the most common frame size for indoor blower motors.
  • If the original motor has the same frame size, the original mounting bracket should work.
  • If not, a new motor mount may be required.
    • The belly band must fit the motor properly.
    • It should be tight enough to prevent the motor from shifting on start-up

  1. Remove the blower assembly from the unit.
  2. Loosen the blower set screw.
  3. Remove the motor mount from the blower housing.
  4. Remove the motor from the motor mounting bracket.
  5. Position the new motor into the mounting bracket.
    1. Do not cover any motor vents with the bracket.
  6. Reassemble the motor mount to the blower housing with the new motor in place and the electrical connections facing down.
    1. Position the electrical connections between 4 and 8 o’clock.
  7. Center the blower in the blower housing.
  8. Position the blower set screw on the flat portion of the shaft, tighten securely.
  9. Replace the blower into the equipment.

Electrical Connections:

  • Evergreen electrical connections consist of three sets of motor leads –
    High Voltage Power Leads
    • Connected directly to Line Power
    • Powered at all times the unit is powered.
    High Voltage Communication Signal Leads
    • Connected to the control terminals that previously operated the PSC Motor
    Low Voltage Communication Signal Leads
    • Connected to the thermostat terminals of the control
  • The motor comes with a yellow jumper installed in the electrical plug and a white jumper shipped with the motor.
  • These jumpers are used to select the voltage in which the motor will be used.
    • If the motor is being installed in a 230V application, leave the yellow jumper installed in the motor plug.
    • If the motor is being used in a 115V application, remove the yellow jumper and replace it with the white jumper.
High Voltage Power Wires:
  • A Black Lead and a White Lead.
  • Provide operating power to the motor.
  1. Connect the Black L1 wire of the Motor to Line Voltage
    1. L1 on 115VAC systems.
    2. L1 on 230VAC systems.
  2. Connect the White L2/N wire to L2 or N
    1. L2 on 230 VAC systems
    2. N on 115VAC systems
  3. Connect the Green w/Yellow stripe ground wire to any cabinet ground within reach.
High Voltage Signal Wires:
  • A Black Lead and a Red Lead.
  • These leads determine the Horse Power selection and give the motor a run command.
    • When high voltage appears on these signal leads, the motor will operate at its lowest speed at the predetermined Horse Power rating.
  • Connected as follows:
    Red only with Black taped off
    Lowest Horse Power rating
    Black only with Red taped off
    Mid Horse Power rating
    Black and Red together
    Highest Horse Power rating
  1. Connect the lead(s) in parallel to all of the motor outputs from the control.
    • IE, if the control wants the motor to operate for any reason – High Heat, Low Heat, High Cool, Low Cool, Fan Only, the signal lead(s) receive high voltage power.
  2. Identify the horse power rating of the original PSC motor.
  3. Use the chart in the installation instructions to determine which High Voltage communication connection(s) to use for the desired horsepower rating.
Low Voltage Communication Signal Wires:
These wires communicate to the motor that there is a call for Heat or Cool and the motor speed must be modified.
High Speed
Medium High Speed – (Available for ‘Y’ connection – See Diagram Below)
Medium Low Speed
Low Speed – (Available for ‘Y’ connection – See Diagram Below)
Common (Low Voltage)
  • Evergreen motor speed is selected by the low voltage inputs powered directly from the system thermostat terminals.
  • The Low Voltage Communication Signal Wires are connected to the thermostat terminals on the control board.
  • Unused Motor Communication Signal Wires are taped off and not used.
  1. Connect the Low Voltage Signal COMMON wire to the common thermostat terminal.
  2. Connect the desired speed(s) – Low Voltage signal wire(s) – to the appropriate HVAC System thermostat connection(s).
  3. Select Low Voltage Communication wires for speeds that best suit operation of the equipment.
    • Select a heating speed that operates the equipment within the correct temperature rise for heating.
    • Select a cooling speed that gives approximately 400 cfm per ton of cooling.
  4. If the same motor speed is required for both Heating and Cooling operation, you must use the ‘Y’ connection provided with the motor.
    • Follow the installation instructions with the motor to apply it.
Important Note:
The ‘Y’ connection can only be used with the Orange or White Motor Leads

Labeling & Data Entry:

  1. Install the System ID Label on the HVAC system near the existing wiring diagram.
  2. Enter the Evergreen data.
  3. Record the Horse Power of the motor and the Date of Installation for future reference if needed.

Post-Installation of the Motor:

  1. Confirm airflow is matched to the systems performance requirements.
  2. Measure airflow with industry accepted instruments.
  3. Confirm the temperature rise on all fossil fuel heating systems to meet the OEM data plate specifications.
  4. Adjust the speed selections to achieve the design CFM per ton of cooling.

If you’d like to see an install guide for replacing a belt drive blower motor, leave us a comment below with some details of your project. You can also find Evergreen replacement motors & additional details via the cfm eStorefront.

Download the original service letter:
Evergreen-motor_Tech-Tips-TT-01-17_April-2017.pdf (343 downloads)

Will Grauberger
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