102
SERVICING
3. High voltage is present at the motor all the time. Motor
operation is controlled through the low voltage motor in-
terface board that provides an output voltage to the mo-
tor end bell. This voltage output determines the CFM,
which the motor wil provide.
A Green LED light, located on the integrated ignition con-
trol, next to the fuse, indicates the airflow that the motor is
supposed to be delivering. The number of blinks depends
upon the positioning of the pin selector switches on the inte-
grated ignition control. The number of blinks multiplied by
100 yields the programmed CFM (Example: 10 Blinks x 100
= 1000 CFM). The indicated CFM may vary, depending on
the mode of operation and the signals being sent to the
control board at the time.
ECM/ICM Control Connections
EMC/ICM control connections are made thourgh the ther-
mostat connections on the integrated ignition control. No
other control connections are needed.
NOTE: An inductor (Factor Power Choke Correction) is re-
quired when powering the 3/4 and 1 horsepower motors with
115 volts (inductor pictured below). The operation of this in-
ductor is to reduce the line current by storing the electrical
energy in a magnetic field, such that the voltage AC wave-
form leads the current AC waveform. In other words, the
inductor reduces line current which extends the life of the
3/4 and 1 horsepower motors. The furnaces requiring an in-
ductor are shown in the following chart.
80% Models 90% Models 95% Models
*MV80704BXA *CV90704CXA GMV950704CXA
*MV90805CXA *MV90704CXA GMV950905DXA
*MV81155CXA *CV90905DXA GMV951155DXA
*MV90905DXA
*MV91155DXA
IMPORTANT: If the inductor fails, there will be no motor
operation since this is the "LINE" power supply, black wire,
from the integrated ignition control to the motor. To deter-
mine if the inductor is at fault, you can bypass by the induc-
tor by disconnecting the black wire from the inductor and
connecting it directly to the motor. If the motor operates
then the inductor will need to be replaced.
Checking ECM/ICM Motors
ECM/ICM motors connect directly to the AC Line Voltage.
DO NOT insert contactors in series with the ECM/ICM Mo-
tor AC Line. The control is powered continuously to insure
reliable start-up. The connector plug is polarized, verify and
reverify correct connector orientation before applying power.
DO NOT force plug into motor and make sure power is off
before inserting power connector. DO NOT apply voltage to
terminals 1 or 2.
Power
Conditioning
Inverter
Motor
Control
HVAC System Control
INPUTS
24 Volts A/C
Compressor
On/Hi/Low
Fan On
Reversing Valve
Aux./Emergency Heat
Capacity Select
Outputs
CFM Demand
ECM/ICM CONTROL FLOW CHART
To Next Page
Loading...
