Page 20
31-5000734 Rev. 0
Indoor Blower Motor
Power Choke
(4 and 5 Ton Only) Blower Motor
(B3)
To Remove Blower From Unit: Remove access panels,
Control box, Bolts and Wiring Jackplugs.
Then Slide Out Front of Unit.
Figure 6.
During blower operation, the ECM motor emits
energy that may interfere with pacemaker operation.
Interference is reduced by both the sheet metal cabinet
and distance.
WARNING
During blower operation, the ECM motor emits energy
that may interfere with pacemaker operation. Interference
is reduced by both the sheet metal cabinet and distance.
The motor communicates with the integrated control via a
2-way serial connection. The motor receives all necessary
functional parameters from the integrated control and does
not rely on a factory program like traditional variable speed
motors. NF80XV units use a three-phase, electronically
controlled D.C. brushless motor (controller converts
single phase a.c. to three phase D.C.), with a permanent-
magnettype rotor (Figure 7). Because this motor has a
permanent magnet rotor it does not need brushes like
conventional D.C. motors.
The stator windings are split into three poles which are
electrically connected to the controller. This arrangement
allows motor windings to turn on and off in sequence by
the controller.
Earlier ECM motors used on other GE Appliances
furnace models are not interchangeable with motors
used on the A80US2V furnace line.
IMPORTANT
A solid-state controller is permanently attached to the
motor. The controller is primarily an A.C. to D.C. converter.
Converted D.C. power is used to drive the motor. The
controller contains a microprocessor which monitors
varying conditions inside the motor (such as motor
workload).
BLOWER MOTOR COMPONENTS
STATOR
(WINDINGS)
BEARING
ROTOR
Figure 7.
The controller uses sensing devices to sense what position
the rotor is in at any given time. By sensing the position of
the rotor and then switching the motor windings on and off
in sequence, the rotor shaft turns the blower.
All NF80XV blower motors use single phase power.
An external run capacitor is not used. The motor uses
permanently lubricated ball-type bearings.
Internal Operation
The motor is controlled via serial communication between
the integrated control on the furnace and the controller
attached to the motor shell. The messages sent back
and forth between the two controls serve to communicate
rotational direction, demand, motor size, current draw,
torque, and rpm, among other variables.
Motor rpm is continually adjusted internally to maintain
constant static pressure against the blower wheel. The
controller monitors the static work load on the motor
and motor ampdraw to determine the amount of rpm
adjustment. Blower rpm may be adjusted any amount
in order to maintain a constant cfm as shown in Blower
Ratings Tables. The cfm remains relatively stable over a
broad range of static pressure. Since the blower constantly
adjusts rpm to maintain a specified cfm, motor rpm is not
rated. Hence, the terms “cool speed”, “heat speed ” or
“speed tap” in this manual, on the unit wiring diagram and
on blower B3, refer to blower cfm regardless of motor rpm.
Initial Power Up
When line voltage is applied to B3, there will be a large
inrush of power lasting less than 1/4 second. This inrush
charges a bank of DC filter capacitors inside the controller.
If the disconnect switch is bounced when the disconnect is
closed, the disconnect contacts may become welded. Try
not to bounce the disconnect switch when applying power
to the unit.
