SERVICING
70
1. Remove unit wiring from disconnect switch and wire a test
cord to the disconnect switch.
NOTE:
The wire size of the test cord must equal the line wire
size and the fuse must be of the proper size and type.
2. With the protective terminal cover in place, use the three
leads to the compressor terminals that were discon-
nected at the nearest point to the compressor and
connect the common, start and run clips to the respective
leads.
3. Connect good capacitors of the right MFD and voltage
rating into the circuit as shown.
4. With power ON, close the switch.
WARNING
Line Voltage now present.
A. If the compressor starts and continues to run, the cause
for failure is somewhere else in the system.
B. If the compressor fails to start - replace.
COPELAND COMPRESSOR
03 A 12345 L
YEA R
M ONTH
SER IAL
NUM BER
PLANT
S-18 TESTING CRANKCASE HEATER (OP-
TIONAL ITEM)
The crankcase heater must be energized a minimum of four
(4) hours before the condensing unit is operated.
Crankcase heaters are used to prevent migration or accumu-
lation of refrigerant in the compressor crankcase during the
off cycles and prevents liquid slugging or oil pumping on start
up.
A crankcase heater will not prevent compressor damage due
to a floodback or over charge condition.
WARNING
Disconnect ALL power before servicing.
1. Disconnect the heater lead in wires.
2. Using an ohmmeter, check heater continuity - should test
continuous. If not, replace.
NOTE:
The positive temperature coefficient crankcase heater
is a 40 watt 265 voltage heater. The cool resistance of the
heater will be approximately 1800 ohms. The resistance will
become greater as the temperature of the compressor shell
increases.
S-21 CHECKING REVERSING VALVE AND SO-
LENOID
Occasionally the reversing valve may stick in the heating or
cooling position or in the mid-position.
When stuck in the mid-position, part of the discharge gas
from the compressor is directed back to the suction side,
resulting in excessively high suction pressure. An increase
in the suction line temperature through the reversing valve can
also be measured. Check operation of the valve by starting
the system and switching the operation from COOLING to
HEATING cycle.
If the valve fails to change its position, test the voltage (24V)
at the valve coil terminals, while the system is on the
COOLING cycle.
All heat pumps and ComfortNet
TM
heat pumps wired in
legacy
- If no voltage is registered at the coil terminals, check
the operation of the thermostat and the continuity of the
connecting wiring from the "O" terminal of the thermostat to
the unit.
ComfortNet heat pumps only
-
Check voltage (24VAC) at
the non-insulated terminal E22 on the UC control board (RVS
on silkscreen) and "C" terminal on the 7-pin or 4-pin connec-
tor on the UC control
If voltage is registered at the coil, tap the valve body lightly
while switching the system from HEATING to COOLING, etc.
If this fails to cause the valve to switch positions, remove the
coil connector cap and test the continuity of the reversing
valve solenoid coil. If the coil does not test continuous -
replace it.
If the coil test continuous and 24 volts is present at the coil
terminals, the valve is inoperative - replace it.
S-24 TESTING DEFROST CONTROL
LEGACY MODELS:
COMFORTNET
TM
UNITS:
To check the defrost control for proper sequencing, proceed
as follows: With power ON; unit not running.
1. Set thermostat to call for heating.
2. Press
TEST
and
RECALL
buttons simultaneously for
approximately 3 seconds, then release them. System
should go into defrost immediately.
3. Using VOM check for voltage across terminals "C & O".
Meter should read 24 volts (skip this step if system a fully
communicating system)
4. Visually inspect to see that the frost is gradually melting
on the coil and the compressor is running.
5. Using VOM check for voltage across "W2 & C" terminals
on the board. You should read 24 volts.
6. If not as above, replace control board.
7. Set thermostat to off position and disconnect power
before removing any jumpers or wires.