Service manual

SERVICING
32
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
Y
EAR
MONTH
SERIAL
NUMBER
PLANT
S-18 TESTING CRANKCASE HEATER
(OPTIONAL 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 SOLENOID
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.
If no voltage is registered at the coil terminals, check the
operation of the thermostat an the continuity of the connect-
ing wiring from the "O" terminal of the thermostat to the unit.
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.
S-40 AR*F & MBR ELECTRONIC BLOWERS
TIME DELAY RELAY
The MBR contains an Electronic Blower Time Delay Relay
board, B1370735. This board provides on/off time delays for
the blower motor in cooling and heat pump heating demands
when “G” is energized.
During a cooling or heat pump heating demand, 24Vac is
supplied to terminal “G” of the EBTDR to turn on the blower
motor. The EBTDR initiates a 7 second delay on and then
energizes it’s onboard relay. The relay on the EBTDR board
closes it’s normally open contacts and supplies power to the
blower motor. When the “G” input is removed, the EBTDR
initiates a 65 second delay off. When the 65 seconds delay
expires the onboard relay is de-energized and it’s contacts
open and remove power from the blower motor.
During an electric heat only demand, “W1” is energized but
“G” is not. The blower motor is connected to the normally
closed contacts of the relay on the EBTDR board. The other
side of this set of contacts is connected to the heat
sequencer on the heater assembly that provides power to the
first heater element. When “W1” is energized, the sequencer
will close it’s contacts within 10 to 20 seconds to supply
power to the first heater element and to the blower motor
through the normally closed contacts on the relay on the
EBTDR. When the “W1” demand is removed, the sequencer
opens it contacts within 30 to 70 seconds and removes power
from the heater element and the blower motor.
The EBTDR also contains a speedup terminal to reduce the
delays during troubleshooting of the unit. When this terminal
is shorted to the common terminal, “C”, on the EBTDR board,
the delay ON time is reduced to 3 seconds and the delay OFF
time is reduced to 5 second.
Two additional terminals, M1 and M2, are on the EBTDR
board. These terminals are used to connect the unused
leads from the blower motor and have no affect on the board’s
operation.