Checking High Pressure Control; Checking Low Pressure Control; Checking High And Low Pressure Switch Voltage; Checking Capacitor - Daikin ComfortNet DX16TC Series Service Instructions Manual

SERVICING
S-12 CHECKING HIGH PRESSURE CONTROL
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
The high pressure control capillary senses the pressure in the
compressor discharge line. If abnormally high condensing
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 pres-
sure control, with wire removed. If not continuous, the
contacts are open.
2. Attach a gauge to the dill valve port on the base valve.
With power ON:
WARNING
Line Voltage now present.
3. Start the system and place a piece of cardboard in front of
the condenser coil, raising the condensing pressure.
4. Check pressure at which the high pressure control cuts-
out. If it cuts-out at 610 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.
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 21 PSIG for heat pumps and 55 PSIG for air con-
ditioners. It will automatically cut-in (close) at approximately
50 PSIG for heat pumps and 95 PSIG for air conditioners.
Test for continuity using a VOM and if not as above, replace
the control.
S-14 CHECKING HIGH AND LOW PRESSURE
SWITCH VOLTAGE
The HPC and LPC are wired in series so output at both switches
should be the same when switches are closed voltage reading
should be 6.5vdc or 8.0vac. NOTE: the Discharge Thermostat
is wired in series with the HPC if DT is open you will read input
voltage on the HPC and no voltage on the output of HPC or
LPC.
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 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.
The line side of this capacitor is marked with "COM" and is
wired to the line side of the circuit.

S-15A RESISTANCE CHECK USING A DIGITAL

MULTI-METER

HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
Check for Digital Test
1. Set the meter on Ohm range (Set it at lease 1000 Ohm
=1k).
WARNING
Discharge capacitor through a 20 to 30 OHM
resistor before handling.
2. Connect the Meter leads to the Capacitor terminals.
3. Digital meter will show a reading momentarily (Figure 1).
Note the reading.
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