Page 12 # 48306B006
Charge Using Weigh-In Method (Fixed Orifice/TXV
Systems)
If the system is void of refrigerant, or if the outdoor
ambient temperature is cool, first locate and repair any
leaks then use the weigh-in method to charge the unit.
1. Recover the refrigerant from the unit.
2. Conduct a leak check, then evacuate as previously
outlined.
3. Weigh in the charge according to the total amount
shown on the unit nameplate.
If weighing facilities are not available or if unit is being
charged during warm weather, follow one of the other
procedures outlined below.
Charge Using Subcooling Method (Fixed Orifice/TXV
Systems) – Outdoor Temperatures 65°F or Above
If charging a fixed orifice or TXV system when the outdoor
ambient temperature is 65°F or above, the subcooling
method can be used to charge the unit.
1. With the manifold gauge hose still on the liquid
service port and the unit operating stably, use a digital
thermometer to record the liquid line temperature. For
best results, use the same digital thermometer to
Cooling Cycle
Figure 12
Use gauge ports on suction line valve and liquid line valve for evacuating refrigerant lines and indoor coil. Use
suction gauge port to measure suction pressure during charging.
OUTDOOR COIL
DEFROST THERMOSTAT
EXPANSION/CHECK VALVE
BIFLOW
FILTER / DRIER
TO
HCFC-22
DRUM
LOW
PRESSURE
HIGH
PRESSURE
COMPRESSOR
REVERSING VALVE
SUCTION
LINE
VALVE
MUFFLER
NOTE - ARROWS INDICATE
DIRECTION OF
REFRIGERANT FLOW
SUCTION
SERVICE
PORT
EXPANSION/CHECK VALVE
INDOOR UNIT
OUTDOOR UNIT
LIQUID
LINE
SERVICE
PORT
GAUGE MANIFOLD
DISTRIBUTOR
INDOOR
COIL
check both the outdoor ambient and the liquid line
temperatures.
2. At the same time, record the liquid line pressure reading.
3. Use a temperature/pressure chart for HCFC-22 to
determine the saturation temperature for the liquid line
pressure reading.
4. Subtract the liquid line temperature from the satura-
tion temperature (according to the chart) to determine
subcooling.
_____ ° Saturation Temperature °F
_____ ° Liquid Line Temperature °F
_____ ° Subcooling Value °F
–
=
5. Compare the subcooling value with those shown in
Table 6. If subcooling is greater than shown, recover
some refrigerant. If subcooling is less than shown,
add some refrigerant.
Charge Using Superheat Method (Fixed Orifice Sys-
tems) – Outdoor Temperatures 65°F or Above
1. With the manifold gauge hose on the suction service
port and the unit operating stably, use a digital ther-
mometer to record the suction line temperature.
2. At the same time, record the suction line pressure
reading.
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