Daikin DCH048 SERIES, Service Instructions Manual

Page: 30 / 139

SERVICING
30
U
NDERCHARGE
An undercharged heat pump on the heating cycle will cause
low discharge pressure resulting in low suction pressure and
frost accumulation on the outdoor coil.
P
OOR
“T
ERMINATING
” S
ENSOR CONTACT
The unit’s defrost terminating sensor must make good
thermal contact with the outdoor coil tubing. Poor contact
may not terminate the unit’s defrost cycle quickly enough to
prevent the unit from cutting out on high discharge pressure.
M
ALFUNCTIONING
R
EVERSING
V
ALVE
- T
HIS MAY BE DUE
TO
:
1. Solenoid not energized - In order to determine if the
solenoid is energized, touch the nut that holds the
solenoid cover in place with a screwdriver. If the nut
magnetically holds the screwdriver, the solenoid is
energized and the unit is in the cooling cycle.
2. No voltage at unit’s solenoid - Check unit voltage. If
no voltage, 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 airflow
through the indoor coil. If the valve does not shift, tap
it
lightly on both ends with a screwdriver handle. DO
NOT TAP THE VALVE BODY . If the unit is on the
cooling cycle, raise the discharge pressure by re-
stricting airflow through the outdoor coil. If the valve
does not shift after the above attempts, cut the unit off
and wait until the discharge and suction pressure
equalize, and repeat above steps. If the valve does not
shift, replace it.
S-50 CHECKING HEATER LIMIT CONTROL(S)
(OPTIONAL ELECTRIC HEATERS)
Each individual heater element is protected with an automatic
rest limit control connected in series with each element to
prevent overheating of components in case of low airflow.
This limit control will open its circuit at approximately 150°F.
to 160°F and close at approximately 110°F.
WARNING
Disconnect 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 control
is open - replace if necessary. Make sure the limits are
cool before testing.
IF FOUND OPEN - REPLACE - DO NOT WIRE AROUND .
S-100 REFRIGERATION REPAIR PRACTICE
DANGER
Always remove the refrigerant charge in a proper
manner before applying heat to the system.
When repairing the refrigeration system:
WARNING
Disconnect ALL power before servicing.
1. Never open a system that is under vacuum. Air and
moisture will be drawn in.
2. Plug or cap all openings.
3. Remove all burrs and clean the brazing surfaces of the
tubing with sand cloth or paper. Brazing materials do not
flow well on oxidized or oily surfaces.
4. Clean the inside of all new tubing to remove oils and pipe
chips.
5. When brazing, sweep the tubing with dry nitrogen to
prevent the formation of oxides on the inside surfaces.
6. Complete any repair by replacing the liquid line drier in the
system, evacuate and charge.
BRAZING MATERIALS
Copper to Copper Joints - Sil-Fos used without flux (alloy
of 15% silver, 80% copper, and 5% phosphorous). Recom-
mended heat 1400°F.
Copper to Steel Joints - Silver Solder used without a flux
(alloy of 30% silver, 38% copper, 32% zinc). Recommended
heat - 1200°F.
S-101 LEAK TESTING
(NITROGEN OR NITROGEN-TRACED)
To avoid the risk of fire or explosion, never use
oxygen, high pressure air or flammable gases for leak
testing of a refrigeration system.
WARNING