Checking Loss Of Charge Protection; Checking High Pressure Control - Daikin DCG Series Service Instructions Manual

SERVICING
5. Using a VOM, check for 240 volts from L1 at contactor to
terminal 4 of relay. Should read 240 volts. Next check
from L1 at contactor to terminal 2 of relay. Should read
240 volts.
If not as above, replace relay.
On the 5 ton units with the EEM motor, a standard fan relay
is used.
WARNING
Disconnect ALL power before servicing.
Turn power off.
Testing relay holding coil
1. Remove the leads from the holding coil.
2. Using an ohmmeter, test across the coil terminals 1 and
3. If the coil does not test continuous, replace the relay.
Testing relay contacts
WARNING
Disconnect ALL power before servicing.
Turn power off.
1. Using a VOM, test resistance across relay terminals 2
and 4. Should read open.
2. Turn power on.
3. Apply 24 volts to coil terminals 1 and 3.
4. Using a VOM, check for 24 volts from terminals 3 and 2
of relay. Should read 24 volts. If no voltage, check low
voltage wiring from transformer to relay. If voltage present,
proceed to step 5.
5. Using a VOM, check for 24 volts from terminals 3 and 4
of relay. Should read 24 volts.
If not as above, replace relay.
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
discharge 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.
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