Service manual

SERVICING
29
S-7 CHECKING CONTACTOR AND/OR RELAYS
The compressor contactor and other relay holding coils are
wired into the low or line voltage circuits. When the control
circuit is energized the coil pulls in the normally open con-
tacts or opens the normally closed contacts. When the coil
is de-energized, springs return the contacts to their normal
position.
WARNING
Disconnect Electrical Power Supply:
1. Remove the leads from the holding coil.
2. Using an ohmmeter, test across the coil terminals.
If the coil does not test continuous, replace the relay or
contactor.
S-8 CHECKING CONTACTOR CONTACTS
WARNING
Disconnect Electrical Power Supply:
1. Disconnect the wire leads from the terminal (T) side of
the contactor.
2. With power ON, energize the contactor.
WARNING
LINE VOLTAGE NOW PRESENT
VOLT/OHM
METER
T1
T2
L1L2
CC
Ohmmeter for testing holding coil
Voltmeter for testing contacts
TESTING COMPRESSOR CONTACTOR
3. Using a voltmeter, test across terminals.
A. L2 - T1 - No voltage indicates CC1 contacts open.
If a no voltage reading is obtained - replace the contactor.
S-9 CHECKING FAN RELAY CONTACTS
The fan relays are incorporated into the control board. See
sections S-23 for checking control board.
NOTE: Some variation over time has occurred in the fan
relays used. Refer to the unit wiring diagram for terminal
identification.
S-15 CHECKING CAPACITOR
CAPACITOR, RUN
A run capacitor is wired across the auxiliary and main wind-
ings of a single phase permanent split capacitor motor. The
capacitors primary function is to reduce the line current while
greatly improving the torque characteristics of a motor. This
is accomplished by using the 90° phase relationship be-
tween 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 im-
proving the power factor.
CAPACITOR, START
SCROLL COMPRESSOR MODELS
Hard start components are not required on Scroll compres-
sor equipped units due to a non-replaceable check valve
located in the discharge line of the compressor. However
hard start kits are available and may improve low voltage
starting characteristics.
This check valve closes off high side pressure to the com-
pressor after shut down allowing equalization through the
scroll flanks. Equalization requires only about one or two
seconds during which time the compressor may turn back-
wards.
To prevent the compressor from starting and running back-
wards a Time Delay Relay (Cycle Protector) has been added
to the low voltage circuit.
NOTE: K3 series scroll compressors have an anti-rota-
tion device and equalizing mechanism incorporated into the
compressor and will equalize in 0.2 to 0.3 seconds. These
compressors will operate correctly without a Time Delay
Relay.
MODELS EQUIPPED WITH A HARD START DEVICE
A start capacitor is wired in parallel with the run capacitor
to increase the starting torque. The start capacitor is of the
electrolytic type, rather than metallized polypropylene as
used in the run capacitor.
A switching device must be wired in series with the capaci-
tor to remove it from the electrical circuit after the compres-
sor starts to run. Not removing the start capacitor will over-
heat the capacitor and burn out the compressor windings.
These capacitors have a 15,000 ohm, 2 watt resistor wired
across its terminals. The object of the resistor is to dis-
charge the capacitor under certain operating conditions,
rather than having it discharge across the closing of the
contacts within the switching device such as the Start Re-
lay, and to reduce the chance of shock to the servicer. See
the Servicing Section for specific information concerning
capacitors.