Checking Transformer And Control Circuit; S-16A Checking Air Circulator Blower Motor (Ecm) - Goodman Amana ComfortNet GMVC8 Service Instructions Manual

SERVICING
If the anticipator current draw is unknown, then a current
amp draw should be measured to determine the anticipator
setting. Use an amprobe as shown in the following drawing.
Checking Heating Anticipator Current (Amp) Draw
Cooling Anticipator
The cooling anticipator is a small heater (resistor) in the
thermostat. During the "OFF" cycle it heats the bimetal el-
ement helping the thermostat call for the next cooling cycle.
This prevents the room temperature from rising too high be-
fore the system is restarted. A properly sized anticipator
should maintain room temperature within 1 1/2 to 2 degrees.
The anticipator is fixed in the subbase and is not to be re-
placed. If the anticipator should fail for any reason, the sub-
base must be changed.
S-4 CHECKING TRANSFORMER AND Control
CIRCUIT
A step-down transformer 120 volt primary to 24 volt second-
ary, 40 VA (Heating and Cooling Models) supplies ample
capacity of power for either operation.
HIGH VOLTAGE
D ALL
ISCONNECT POWER BEFORE SERVICING OR
CHANGING ANY ELECTRICAL WIRING.
F
SOURCES MAY BE PRESENT. AILURE TO DO SO MAY CAUSE
PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
1. Remove blower compartment door to gain access to the
thermostat low voltage wires located at the furnace inte-
grated control module.
2. Remove the thermostat low voltage wires at the furnace
integrated control module terminals.
With Power On (and Door Interlock Switch closed):
WARNING
L
INE VOLTAGE NOW PRESENT
10 TURNS OF
THERMOSTAT WIRE
(From "W" on thermostat)
STATIONARY JAW
OF AMPROBE
READS 4 AMPS
CURRENT DRAW
WOULD BE .4 AMPS
WARNING
M
ULTIPLE POWER
3. Use a voltmeter, check voltage across terminals R
and C. Must read 24 VAC.
4. No voltage indicates faulty transformer, open fuse,
bad wiring, bad splice, or open door interlock switch.
5. Check transformer primary voltage at incoming line
voltage connections, fuse, splices, and blower door
interlock switch.
6. If line voltage is available to the primary side of trans-
former and not at secondary side, the transformer is
inoperative. Replace.
7. After completing check and/or replacement of trans-
former and check and/or repair of control circuit, rein-
stall blower compartment door.
8. Turn on electrical power and verify proper unit opera-
tion.
S-16A CHECKING AIR CIRCULATOR BLOWER
MOTOR (ECM)
Description
These models utilize an Emerson, 4-wire variable speed
ECM blower motor. The ECM blower motor provides con-
stant CFM.
The motor is a serially communicating variable speed mo-
tor. Only four wires are required to control the motor: +Vdc,
Common, Receive, and Transmit.
The +Vdc and Common wires provide power to the motor's
low voltage control circuits. Typical supply voltage is 9-15
volts DC.
ECM Control Connections
ECM control connections are made through 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 inductor is to reduce the line current by storing the
electrical energy in a magnetic field, such that the voltage
AC waveform 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.
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 in-
ductor by disconnecting the black wire from the inductor
and connecting it directly to the motor. If the motor oper-
ates then the inductor will need to be replaced.
73