Lennox G61MPV Service Manual page 42

PW RX
LED LED
Off Blink
Blink Blink
Blink Off
Off Off
Motor rpm is continually adjusted internally to maintain
constant cfm. The controller monitors the static work load on
the motor and motor amp-draw 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 manu-
al, on the unit wiring diagram and on blower B3, refer to blower
cfm regardless of motor rpm.
The unit control indicates the desired cfm. The blower will
maintain the desired cfm as long as external static pressure
does not exceed 0.8". If the system exceeds this amount, the
blower may enter a cut back", mode wherein it then slows
down to protect itself from electrical damage. During this cut
back" mode the unit control will still indicate the same desired
cfm regardless of actual motor rpm.
When Harmony is used, speed taps are overridden and a
PWM signal generated by the Harmony controller continuous-
ly varies motor speed based upon zone demands.
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 discon-
nect switch is bounced when the disconnect is closed, the dis-
connect contacts may become welded. Try not to bounce the
disconnect switch when applying power to the unit.
Motor Start-Up
When B3 begins start-up, the motor gently vibrates back and
forth for a moment. This is normal. During this time the elec-
tronic controller is determining the exact position of the rotor.
Once the motor begins turning, the controller slowly eases
the motor up to speed (this is called soft-start"). The motor
may take as long as 10-15 seconds to reach full speed. If the
TABLE 27
Emerson Motor Only
TX Motor
Blower
LED
Not
Blink
Rotating
Blink Rotating
Verify 16X4W and motor control hp match. Verify
Not
Blink Turn off power for 1 minute then restart. If motor still
Rotating
does not rotate replace the controller. See Page 109 for
Verify power to the 16X4W. Turn off power then restart.
Not
Off If LED's are still out, replace controller. See Page 109
Rotating
Action
Normal
Normal. PW blink is 100cfm/blink
power to motor control.
further diagnosis.
for further diagnosis.
motor does not reach 200rpm within 13 seconds, the motor
shuts down. Then the motor will immediately attempt a re-
start. The shutdown feature provides protection in case of a
frozen bearing or blocked blower wheel. The motor may at-
tempt to start eight times. If the motor does not start after the
eighth try, the controller locks out. Reset controller by momen-
tarily turning off power to unit.
The DC filter capacitors inside the controller are connected
electrically to the speed tap wires. The capacitors take
approximately 5 minutes to discharge when the disconnect
is opened. For this reason it is necessary to wait at least 5
minutes after turning off power to the unit before attempt-
ing to change speed taps.
Disconnect power from unit and
wait at least five minutes to allow
capacitors to discharge before at-
tempting to adjust motor speed tap
settings. Failure to wait may cause
personal injury or death.
External Operation (Speed Tap Priority)
Figures 12 and 11 show the two quick-connect jacks (J48
and J49) which connect the motor to the G61MPV. Jack
J48 is the power plug and jack J49 connects the unit con-
trols to the motor.
Jack J48 is the power plug. Line voltage must be applied to
J48 pins 4 and 5 in order for the motor to operate. When
using 120VAC pins 1 and 2 must be jumpered.
Jack J49 connects the unit controls to the motor. The motor
assigns priority to J49 pin 2 so that if a call for cooling and a
call for heating are concurrent, heating call overrides and
the blower operates on high speed heating tap. See
Page 108 for more detailed speed tap operation.
Page 42
DANGER