5
Charge Refrigerant Lines
NOTE: Refrigerant lines must be charged by a licensed, EPA
certified refrigeration technician in accordance with established
procedures.
The outdoor condensing unit should be charged during warm
weather. However, applications arise in which charging must
occur in the colder months. The method of charging is
determined by the system’s refrigerant expansion device and the
outdoor ambient temperature. Choose one of the following
charge methods based on the system’s refrigerant expansion
device and the outdoor ambient temperature.
Measure the Liquid Line Temperature and the Outdoor
Ambient Temperature
1. Connect the manifold gauge set to the service valve ports as
follows:
■
Low pressure gauge to suction line service valve
■
High pressure gauge to liquid line service valve
2. Close manifold gauge set valves.
3. Connect the center manifold hose to an upright cylinder of
refrigerant (R-22).
4. If room temperature is below 70°F (21ºC), set the room
thermostat to call for heat. This will create the necessary load
for properly charging the system in the cooling cycle.
5. When the heating demand has been satisfied, switch the
thermostat to cooling mode with a set point of 68°F.
6. When pressures have stabilized, use a digital thermometer to
record the liquid and suction line temperatures.
7. Use a digital thermometer to record the outdoor ambient
temperature.
NOTE: The outdoor temperature will determine which charging
method to use.
Charge Using Weigh-In Method (Fixed Orifice/Thermal
Expansion Valve Systems)
Use this method if the system is void of refrigerant, or if the
outdoor ambient temperature is cool.
1. Locate and repair any leaks.
2. If necessary, recover the refrigerant from the condensing unit.
3. Conduct a leak check, then evacuate as previously outlined.
4. Weigh in the charge according to the total amount shown on
the condensing unit nameplate.
NOTE: If weighing facilities are not available or if the condensing
unit is being charged during warm weather, follow one of the
other charging methods.
IMPORTANT:
■
Refrigerant charge adjustment will be required for line set
lengths greater than 15 ft (4.6 m) and for non system-
matched evaporator coils.
■
The condensing unit is factory-charged with the proper
refrigerant charge amount for a matching evaporator and
15 ft (4.6 m) of refrigerant line. Refer to the condensing unit
rating plate for the exact amount of this factory charge.
■
Adjustment of the refrigerant charge will be necessary based
on the system combination and line length. To adjust the
refrigerant size for increased line lengths, add the following
amount of refrigerant.
For line set lengths greater than 15 ft (4.6 m), add refrigerant
by weighing in 0.60 oz per ft of
³⁄₈
" (1 cm) O.D. liquid line.
■
If necessary, adjust the refrigerant charge for compatibility
with the evaporator coil.
Charge Using Sub-cooling Method (Thermal Expansion Valve
Systems)—Outdoor Temperatures 65°F (18ºC) or Above
Use this method if charging a Thermal Expansion Valve system
when the outdoor ambient temperature is 65°F (18ºC) or above.
1. Attach the manifold gauge hose to the liquid service port.
2. If the condensing unit pressures are stable, use a digital
thermometer to record the liquid line temperature.
3. Record the liquid line pressure reading.
4. Use a temperature/pressure chart for refrigerant (R-22) to
determine the saturation temperature for the liquid line
pressure reading.
5. Subtract the liquid line temperature from the saturation
temperature to determine sub-cooling. See Sub-cooling Values
for Thermal Expansion Valve Systems chart.
_____ ° (Saturation Temperature °F) - _____ ° (Liquid Line
Temperature °F) = _____ ° (Sub-cooling Value °F)
6.
Compare the sub-cooling value with those shown in Sub-cooling
Values for Thermal Expansion Valve Systems chart.
■
If sub-cooling is greater than shown, recover some
refrigerant.
■
If sub-cooling is less than shown, add some refrigerant.
Charge Using Superheat Method (Fixed Orifice
Systems)—Outdoor Temperatures 65°F (18ºC) or Above
Use this method if charging a fixed orifice system when the
outdoor ambient temperature is 65ºF (18ºC) or above.
1. Attach the manifold gauge hose to the suction service port.
2. If the condensing unit pressures are stable, use a digital
thermometer to record the suction line temperature.
3. Record the suction line pressure reading.
4. Use a temperature/pressure chart for refrigerant (R-22) to
determine the saturation temperature for the suction line
pressure reading.
5. Subtract the saturation temperature from the suction line
temperature to determine the superheat.
_____ ° (Suction Line Temperature °F) - _____ ° (Saturation
Temperature °F) = _____ ° (Superheat Value °F)
6. Compare the superheat value with those shown in the chart
located on the control box cover.
■
If superheat is greater than shown, add some refrigerant.
■
If superheat is less than shown, recover some refrigerant.
Sub-cooling Values for Thermal Expansion Valve Systems
Required Sub-cooling—
∆
ºF
Model
W2H3
W2H4
18
14
10
24
9
3
30
13
8
36
9
14
42
11
3
48
8
9
60
12
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