Major System Components - Lennox MS8 SERIES Installation And Service Procedures

Major System Components

This section describes the following system components.
1. COMPONENT: INDOOR FAN MOTOR
DESCRIPTION:
The indoor fan is driven by a single-phase (115V) AC motor.
The motor adopts step-less speed regulation to operate at
different speeds. The motor speeds are determined by the
output voltage and frequency signal from the indoor control.
A Hall effect sensor, that is located in the end of the motor,
feeds back information to the indoor control to confirm that
the indoor motor is operating at the requested RPM.
TROUBLESHOOTING:
Check wiring connections at indoor control.
Measure resistance between the plug-in pins (if reading
show open or shorted, replace fan motor). Measure
resistance between leads red to brown, red to white and
brown to white. If resistance is 0 ohms or infinite, replace
motor.
2. COMPONENT: INDOOR LOUVER MOTOR
(SWING MOTOR)
DESCRIPTION:
A stepper motor (or step motor) is a brush less, electric
motor that can divide a full rotation into a large number of
steps. The louver motor operates on a 12 VDC input to vary
the indoor air discharge louver to a programmed setting.
Stepper motors effectively
electromagnets arranged around a central gear-shaped
piece of iron. The electromagnets are energized by an
external control circuit, such as a microcontroller. To make
the motor shaft turn, first one electromagnet is given power,
which makes the gear's teeth magnetically attracted to the
electromagnet's teeth. When the gear's teeth are thus
aligned to the first electromagnet, they are slightly offset
from the next electromagnet. So when the next
electromagnet is turned on and the first is turned off, the gear
rotates slightly to align with the next one and from there the
process is repeated. Each of those slight rotations is called a
step, with an integer number of steps making a full rotation.
In that way, the motor can be turned a precise angle.
TROUBLESHOOTING:
* Check wiring connections at indoor control.
* Measure resistance between the plug-in pins (if
readings show open or shorted, replace motor). Normal
reading between red-pink, red-blue, red-orange and
red-yellow should be approximately 135 ohms + 10%.
have multiple toothed
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PHOTO OF INDOOR FAN MOTOR NAME PLATE (18-24 KBTU
UNITS)
Corp. 1244-L9