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If no refrigerant leaks are found and low cooling performance is
suspected, refer to the Checking and Adjusting Refrige rant Charge
section.
Gas Input
The gas input does not require checking unless improper heating
performance is suspected. If a probl em exists, refer to the Start--Up
section.
Indoor Airflow
The heating and/or cooling airflow does not require checking
unl ess improper performan ce is suspected. If a problem exists, be
sure that all supply-- and return--air grilles are open and free from
obstructions, and that the air filter i s clean. When necessary, r efer to
the Indoor Airflow and Airflow Adjustments section to check the
system airflow.
Check Defrost Thermostat
The defrost thermostat is usually located on the lowest liqui d
leaving circuit of the left condenser coil (see Fig. 22). The
thermostat closes at 32_F(0_C) and opens at 65_F(18_C).
Puron Items
Metering Device
(Thermostatic Expansion Valve &
Piston)
This unit uses both a hard shutoff, balance port TXV in the indoor
coil and a piston in each side of the outdoor coil. The TXV
maintains a constant superheat at the evaporator coil exit (cooling
mode) r esulting in higher overall system efficiency.
Pressure Switches
Pressure switches are protective devices wired into control circuit
(low voltage). They shut off compressor if abnormally high or low
pressures are present in the refrigeration circuit. These pressure
switches are specifically designed to operate with Puron (R--410A)
systems. R--22 pressure switches mus t not be used as replacements
for the Puron (R--410A) system.
OF2
OF1
ON
QUIET
SHIFT
120
30
60
60
30
90
INTERVAL TIMER
OFF
P3
DFT
O R W
2
Y C
T2 C C O
DFT
T1 Y
P1
J1
SPEEDUP
Speedup
Pins
Defrost interval
DIP switches
Quiet
Shift
A08020
Fig. 23 -- Defrost Control
Loss of Charge Switch
This switch is located on the liquid line and protects against low
suction pressures caused by such events as loss of charge, low
airflow across indoor coil, dirty filters, etc. It ope ns on a pressure
drop at about 20 psig. If system pressure is above this, switch
should be closed. To check switch:
1. Turn off all power to unit.
2. Disconnect leads on switch.
3. Apply ohm meter leads across switch. You should have
continuity on a good switch.
NOTE: B ecause these switches are attached to refrige ration
system under pressure, it is not advisable to remove this device for
troubleshooting unless you are reasonably certain that a problem
exists. If switch must be removed, remove and recover all system
charge so that pressure gauges read 0 psi. Never open system
without breaking vacuum with dry nitrogen.
677C-- --A