Checking Loss Of Charge Protection; Checking High Pressure Control; Checking Low Pressure Control; Checking Capacitor - Daikin DBG 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 au-
tomatically reset.
1. Using an ohmmeter, check across terminals of high pres-
sure 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 Anal-
ysis 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 wind-
ings 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 mo-
tor 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 compres-
sor after shut down allowing equalization through the scroll
flanks. Equalization requires only about one or two seconds
during which time the compressor may turn backwards.
Your unit comes with a 180-second anti-short cycle to prevent
the compressor from starting and running backwards.
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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