SYSTEM OPERATION
42
motor.
21.
Motor Volts.
This condition occurs if the line voltage is
too low or too high, or if the motors power module gets
too hot. The ECM motor will shut down while the abnor-
mal condition is present. If the abnormal condition is
cleared, the motor will restart. The furnace will be inop-
erable while the motor is off.
Over Voltage.
If the line voltage exceeds 140VAC, the
motor will shut down due to an over voltage condition.
Verify the line voltage to the furnace is within the range
specified on the rating plate.
Under Voltage.
If the line voltage is less than 70VAC,
the motor will shut down due to an under voltage condi-
tion. Verify the line voltage to the furnace is within the
range specified on the rating plate.
Over Temperature.
A high ambient temperatue or a high
loading condition is the most probable cause. Reduce
the ambient temperature and/or motor loading/demand.
22.
Motor Parameters.
This condition occurs if the motor
does not receive all the information is requires to oper-
ate or an event occurs that prevents the motor from run-
ning, or the motor fails to start for (40) consecutive at-
tempts. The diagnostic error code for the this condition
is
b7
. Probable causes are intermittent wiring connec-
tion between the control and motor, an error with the
furnace control, or any of the conditions described in 19,
20, or 21 above.
23.
Low Indoor Airflow.
This condition occurs if the in-
door airflow falls below a calculated minimum value. The
minimum airflow value is calculated from factors defined
in the shared data set. If the airflow falls below the cal-
culated minimum, the furnace will continue to operate
with the reduce airflow. If the furnace was operating at
stage, it will stage back to low in an effort to remedy the
condition. The furnace will halt operation if the airflow
falls to 0 CFM.
The diagnostic error code for the this condition is
b9
.
Probable causes are blocked/clogged filters, blocked
or restrictive ductwork, or undersized ductwork.