How do you test a variable speed switch?

PLACE RED LEAD OF VOLT METER ON CENTER TERMINAL OF THE FEED RATE SWITCH. PLACE BLACK LEAD ON A SUITABLE GROUND. WITH KEY IN THE “ON” POSITION AND P/F DRUM SWITCH IN THE FORWARD POSITION, VOLTAGE SHOULD VARY SMOOTHLY BETWEEN APPROX. 1-3.5 VOLTS D.C. AS THE SWITCH IS DIALED UP AND DOWN.

What causes ECM motors to fail?

A major cause of failure occurs when a blower is applied to an application with static pressure above . 8” WG. This not only shortens the life of an ECM, but also a PSC. With an ECM this will cause a failure of the metal oxide varistor (MOV), a disk in the controller.

How do you diagnose an ECM motor?

Diagnosing ECM Motors

  1. Verify that the correct thermostat input voltage is present at the interface of the main control board on the furnace or air handler.
  2. When checking low-voltage connections, always use the C terminal on the board, never on the ground.

How does a variable speed switch work?

It works through the regulated activation of a field coil, which generates a magnetic field that is transmitted to the input rotor, which in turn transmits it to the output rotor. The higher the intensity of the magnetic field, the higher the speed and torque that are transmitted.

How does a variable speed blower motor work?

How Does it Work? Unlike conventional fan motors, a variable speed blower motor runs at different speeds to precisely control the flow of heated or cooled air throughout your home. Better airflow control means a better balance of temperature and humidity.

Does a variable speed furnace run all the time?

Variable speed furnaces have an air handler that operates at many different speeds depending on the demand for air at any given time. A variable speed air handler runs almost all the time, albeit typically at a low setting that is much quieter than the higher setting that’s used during heating cycles.

How does a variable speed ECM motor work?

The ECM motor keeps track of input from your heating system on a constant basis and adjusts its speed as needed. When less heat is needed, the fan automatically slows down. When more heat is needed or when other factors affect your heating system, such as a dirty filter, the fan speeds up.

What controls a variable speed drive?

Variable speed drives sit between the electrical supply and the motor. Power from the electrical supply goes into a drive and the drive then regulates the power that is fed to the motor. Inside the drive the input power is run through a rectifier, that converts the incoming AC power to DC power.