48
Fan Motor
Fan motor rotates the fan blade that either draws or blows air
through outdoor coil to exchange heat between refrigerant and air.
Motors are totally enclosed to increase reliability. This also
eliminates need for rain shield.
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
Turn off all power to unit before servicing or replacing fan
motor. Be sure unit main power switch is turned off.
!
WARNING
The bearings are permanently lubricated; therefore, no oil ports are
provided.
For suspected electrical failures, check for loose or faulty electrical
connections, or defective fan--motor capacitor. Fan motor is
equipped with thermal overload device in motor windings which
may open under adverse operating conditions. Allow time for
motor to cool so device can reset. Further checking of motor can be
done with an ohmmeter. Set scale on R X 1 position; check for
continuity between three leads. Replace motors that show an open
circuit in any of the windings. Place 1 lead of ohmmeter on each
motor lead. At same time, place other ohmmeter lead on motor case
(ground). Replace any motor that shows resistance to ground, signs
of arcing, burning, or overheating.
Located above the compressor is a single--speed fan motor and fan.
The 180ANA/288ANA air conditioner and heat pump models use
the ECM variable speed fan motor.
The outdoor Integral Control Motor (ECM), is a variable--speed
motor which operates from 450 to 850 rpm. The motor is a dc
permanent magnet--type motor with the electronic controls
integrated into its rear cover. The control package includes a small
diode bridge, capacitors, and power switching devices. It converts
acto dc power and switches thedc power to the motor windings on
and off at various rates to control the motor speed. The speed at
which the motor windings are thus commutated is determined by a
pulse width modulated (PWM) signal which is received from the
control board on the motor control lines.
The PWM signal is created by turning a DC signal on and off once
within a given period of time. The signal on time relative to the
signal total period defines the percent of the PWM. For example, if
the period is 5 sec and the control power is turned on for 1 sec then
off, the signal will remain off for 4 sec before turning on again to
start the next cycle. The PWM is called a 20 percent duty cycle
signal. If the on time is increased to 4 sec of the 5 sec period, the
PWM is called an 80 percent duty cycle. The ECM reads the PWM
signal and increases the motor speed linearly from minimum speed
to maximum speed with the percent duty cycle value of the
supplied PWM signal.
Outdoor Fan Motor
Operation
There are two different types of motors used in the Evolution
2--stage outdoor units. The 286A models use a PSC type fan
motor, and the speed does not change between high and low speed
operation.
On 288ANA models, an ECM fan motor is used to achieve higher
efficiency ratingsof the system. The outdoor unit control energizes
outdoor fan anytime compressor is operating, except for defrost or
low--ambient cooling. The outdoor fan remains energized if a
pressure switch or compressor overload should open. The outdoor
fan motor will continue to operate for one minute after the
compressor shuts off when the outdoor ambient is greater than or
equal to 100°F/37.7°C. This reduces pressure differential for easier
starting on next cycle. On 286A/187ANA models, the outdoor fan
remains energized during the 1--minute compressor staging time
delay.
On 286ANA/187ANA models, the outdoor fan motor is a PSC
type. A fan relay on the control board turns the fan off and on by
opening and closing a high voltage circuit to the motor. It does not
change speeds between low and high stage operation.
On 288ANA/180ANA models, the outdoor fan is an ECM type.
The motor control is continuously powered with high voltage. The
motor speed is determined by electrical pulses provided by the
PWM outputs on the control board. The ECM motor RPM adjusts
to outdoor conditions as described in Table 15. The PWM output
can be measured with a volt meter set to DC volts.
In low ambient cooling (below 55°F/12.7°C), the control board
cycles the fan off and on.
Table 15—Outdoor Fan Motor PWM
Outdoor Temp (DC volts, Tolerance +/-- 2%)
Model
Low Stage
(OAT≤104_F/40_C)
HighStage
(OAT≤104_F/40_C)
Low &High
Stage
(OAT>104_F/40_C)
288ANA024 8.72 9.35 11.9
288ANA036 9.06 10.23 11.9
288ANA048 9.91 11.04 11.9
288ANA060 10.83 11.7 11.9
180ANA024 9.57 10.88 11.90
180ANA036 9.06 10.23 11.90
180ANA048 9.91 11.04 11.90
180ANA060 10.83 11.70 11.90
NOTE: For 288A models in low---a mbient cooling, the PWM output for
both high--- and low---stage equals the value for low---stage
operation below 55_F (12.8_C).
ECM Fan Motor Troubleshooting
If the outdoor fan motor fails to start and run:
S Check the high--voltage supply. The unit need not be
running to check high voltage, but the power must be on.
S If the 230vac is present, use Table 15 to check for proper
control voltage output to the fan motor from the control
board. The control board sends DC voltage signals to the
motor through the terminals labeled PWM1 and PWM2
Set a voltmeter on a DC voltage scale and check across
these terminals.
S First check voltage with the motor disconnected. If no
control voltage is present, check control--board
connections. If connections are good, replace the control
board.
S If voltage is present, reconnect the motor and check
again. Shut down the unit to reconnect the motor and
restart the unit to complete this troubleshooting
procedure. If control voltage is no longer present or
motor fails to respond, check motor connections.
S If connections are good, replace the motor.
