21
513 01 3402 02
to flow from cylinder in upright position. For cylinders equipped
with a dip tube, charge R
−
410A units with cylinder in upright
position and a commercial metering device in manifold hose.
Charge refrigerant into suction
−
line.
Step 13 — System Information
Loss of Charge Switch
The loss of charge switch is a protective device wired into control
circuit (low voltage). It shuts off the compressor if abnormally low
pressures are present in the refrigeration circuit.
NOTE
: Because these switches are attached to refrigeration
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 zero gauge.
Never open system without breaking vacuum with dry nitrogen.
Check Defrost Thermostat
The defrost thermostat is usually located on the lowest liquid
leaving circuit of the left condenser coil (see FIGURE 20). The
thermostat closes at 32
F +/
−
3
F (0
C +/
−
1.7
C) and opens
at 65
F +/
−
5
F (18
C +/
−
2.8
C).
The defrost thermostat signals heat pump that conditions are
right for defrost or that conditions have changed to terminate
defrost. It is a thermally actuated switch clamped to outdoor coil
to sense its temperature.
NOTE
: The defrost thermostat must be located on the liquid side
of the outdoor coil on the bottom circuit and as close to the coil
as possible.
FIGURE 20
Defrost Thermostat
FEEDER TUBE
STUB TUBE
DEFROST
THERMOSTAT
TROUBLESHOOTING
Refer to the Cooling and Heating Troubleshooting Chart
(Table 7) for troubleshooting information.
START
−
UP CHECKLIST
Use the Start
−
Up Checklist.