Checking High Pressure Control; Checking Low Pressure Control; Checking Capacitor - Daikin DCH048 Series Service Instructions Manual

SERVICING
S-11 CHECKING LOSS OF CHARGE PROTEC-
TOR
(Heat Pump Models)
The loss of charge protector senses the pressure in the liquid
line and will open its contacts on a drop in pressure. The low
pressure control will automatically reset itself with a rise in
pressure.
The low pressure control is designed to cut-out (open) at
approximately 22 PSIG. It will automatically cut-in (close) at
approximately 50 PSIG.
Test for continuity using a VOM and if not as above, replace
the control.
S-12 CHECKING HIGH PRESSURE CONTROL
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do so
may cause property damage, personal injury
or death.
The high pressure control senses the pressure in the dis-
charge line. If abnormally high discharge pressures develop,
the contacts of the control open, breaking the control circuit
before the compressor motor overloads. This control is
automatically reset.
1. Using an ohmmeter, check across terminals of high
pressure control, with wire removed. If not continuous, the
contacts are open.
3. Attach a gauge to the access fitting on the liquid line.
With power ON:
4. Start the system and place a piece of cardboard in front
of the condenser coil, raising the condensing pressure.
5. Check pressure at which the high pressure control cuts-
out.
If it cuts-out at 660 PSIG ± 10 PSIG, it is operating normally
(See causes for high head pressure in Service Problem
Analysis Guide). If it cuts out below this pressure range,
replace the control. The control should reset at 420 PSIG ±
25 PSIG.
S-13 CHECKING LOW PRESSURE CONTROL
The low pressure control senses the pressure in the suction
line and will open its contacts on a drop in pressure. The low
pressure control will automatically reset itself with a rise in
pressure.
The low pressure control is designed to cut-out (open) at
approximately 22 PSIG ± 7 PSIG. It will automatically cut-
in (close) at approximately 50 PSIG ± 7 PSIG.
Test for continuity using a VOM and if not as above, replace
the control.
S-15 CHECKING CAPACITOR
CAPACITOR, RUN
A run capacitor is wired across the auxiliary and main
windings 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
between 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
improving 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
compressor 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.
Your unit comes with a 180-second anti-short cycle to
prevent the compressor from starting and running back-
wards.
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 capacitor
to remove it from the electrical circuit after the compressor
starts to run. Not removing the start capacitor will overheat
the capacitor and burn out the compressor windings.
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