Checking Transformer And Control Circuit; Capacitance Check; Checking Capacitor - Goodman Amana AMH8 Service Instructions Manual

SERVICING
The anticipator is a part of the thermostat and if it
should fail for any reason, the thermostat must be re-
placed. Some thermostats have a cycle rate adjust-
ment switch to set cycles per hour.
The heating anticipator setting for furnaces covered in
this manual is 0.70 Amps.
If the anticipator current draw is unknown, then a cur-
rent 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 bi-
metal element helping the thermostat call for the next
cooling cycle. This prevents the room temperature from
rising too high before the system is restarted. A prop-
erly sized anticipator should maintain room tempera-
ture within 1 1/2 to 2 degrees.
The anticipator is fixed in the subbase and is not to be
replaced. If the anticipator should fail for any reason,
the subbase must be changed.
S-4 CHECKING TRANSFORMER AND Control CIRCUIT
A step-down transformer 120 volt primary to 24 volt
secondary, 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 integrated control module.
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
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
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 inter-
lock 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
transformer and not at secondary side, the trans-
former is inoperative. Replace.
7. After completing check and/or replacement of
transformer and check and/or repair of control
circuit, reinstall blower compartment door.
8. Turn on electrical power and verify proper unit op-
eration.
S-10

Capacitance Check

With power On (and Door Interlock Switch closed):
WARNING
L
INE VOLTAGE NOW PRESENT
S-15

CHECKING CAPACITOR

The direct drive motors are of the permanent split ca-
pacitor design. A run capacitor is wired across the aux-
iliary and a portion of the main windings. The capaci-
tors primary function is to reduce the line current while
greatly improving the torque characteristics of a mo-
tor. This is accomplished by using the 90° phase rela-
tionship between the capacitor current and voltage in
conjunction with the motor windings so that the motor
will give two phase operation when connected to a
single phase circuit. The capacitor also reduces the line
current to the motor by improving the power factor to
the load.
D
ISCHARGE CAPACITOR THROUGH A 20 TO 30 OHM RESISTOR
BEFORE HANDLING.
W ARNING
51