Daikin DCG Series Service Instructions Manual

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Contents

SERVICING548. If not as above, replace control board.9. Set thermostat to off position and disconnect powerbefore removing any jumpers or wires.NOTE: Remove jumper across defrost thermostat beforereturning system to service.S-25 TESTING DEFROST THERMOSTAT1. Install a thermocouple type temperature test lead on thetube adjacent to the defrost control. Insulate the leadpoint of contact.2. Check the temperature at which the control closes itscontacts by lowering the temperature of the control. On2 and 2.5 ton units, it should close at 34°F ± 5°F. On 3 thru5 ton units, it should close at 31°F ± 3°F.3. Check the temperature at which the control opens itscontacts by raising the temperature of the control. On 2and 2.5 ton units, it should open at 60°F ± 5°F. On 3 thru5 ton units, it should open at 75°F ± 6°F.4. If not as above, replace control.TROUBLESHOOTINGTHE FOLLOWING INFORMATION IS FOR USE BY QUALI-FIED SERVICE AGENCY ONLY: OTHERS SHOULD NOTATTEMPT TO SERVICE THIS EQUIPMENT.Common Causes of Unsatisfactory Operation of Heat Pumpon the Heating Cycle.I NADEQUATE AIR VOLUME THROUGH INDOOR C OILWhen a heat pump is in the heating cycle, the indoor coil isfunctioning as a condenser. The return air filter must alwaysbe clean, and sufficient air volume must pass through theindoor coil to prevent excessive discharge pressure, and highpressure cut out.OUTSIDE AIR INTO RETURN DUCTDo not introduce cold outside air into the return duct of a heatpump installation. For units with 2-speed motors, do notallow air entering the indoor coil to drop below 65° F. Air belowthis temperature will cause low discharge pressure, thus lowsuction pressure, and excessive defrost cycling resulting inlow heating output. It may also cause false defrosting.UNDERCHARGEAn undercharged heat pump on the heating cycle will causelow discharge pressure resulting in low suction pressure andfrost accumulation on the outdoor coil.POOR “TERMINATING ” SENSOR CONTACTThe unit’s defrost terminating sensor must make goodthermal contact with the outdoor coil tubing. Poor contactmay not terminate the unit’s defrost cycle quickly enough toprevent the unit from cutting out on high discharge pressure.MALFUNCTIONING R EVERSING VALVE - T HIS MAY BE DUE TO :1. Solenoid not energized - In order to determine if thesolenoid is energized, touch the nut that holds thesolenoid cover in place with a screwdriver. If the nutmagnetically holds the screwdriver, the solenoid is ener-gized and the unit is in the cooling cycle.2. No voltage at unit’s solenoid - Check unit voltage. If novoltage, check wiring circuit.3. Valve will not shift:a. Undercharged - check for leaks;b. Valve Body Damaged - Replace valve;c. Unit Properly Charged - If it is on the heating cycle,raise the discharge pressure by restricting airflowthrough the indoor coil. If the valve does not shift, tapit lightly on both ends with a screwdriver handle. DONOT TAP THE VALVE BODY. If the unit is on thecooling cycle, raise the discharge pressure by restrict-ing airflow through the outdoor coil. If the valve does notshift after the above attempts, cut the unit off and waituntil the discharge and suction pressure equalize, andrepeat above steps. If the valve does not shift, replaceit.S-50 CHECKING HEATER LIMIT CONTROL(S)(OPTIONAL ELECTRIC HEATERS)Each individual heater element is protected with an automaticrest limit control connected in series with each element toprevent overheating of components in case of low airflow. Thislimit control will open its circuit at approximately 150°F. to160°F and close at approximately 110°F.WARNINGDisconnect ALL power before servicing.1. Remove the wiring from the control terminals.2. Using an ohmmeter test for continuity across the nor-mally closed contacts. No reading indicates the controlis open - replace if necessary. Make sure the limits arecool before testing.IF FOUND OPEN - REPLACE - DO NOT WIRE AROUND.S-52 CHECKING HEATER ELEMENTSOptional electric heaters may be added, in the quantitiesshown in the spec sheet for each model unit, to provideelectric resistance heating. Under no condition shall moreheaters than the quantity shown be installed.