9
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 Approach 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 65ºF (18ºC) or above.
NOTES:
■ The following procedure is intended as a general guide.
■ Use on Thermal Expansion Valve systems only.
■ For best results, indoor temperature should 70°F (21ºC) to
80°F (27ºC).
■ Monitor system pressures while charging.
1. Record outdoor ambient temperature using a digital
thermometer.
2. Attach high pressure gauge set.
3. Operate condensing unit for several minutes to allow system
pressures to stabilize.
4. Compare stabilized pressures with those provided in the
Normal Operating Pressures chart.
NOTES:
■ Minor variations in these pressures may be expected due
to differences in installations.
■ Significant differences could mean that the system is not
properly charged or that a problem exists with some
component in the system.
■ Pressures higher than those listed indicate that the
system is overcharged.
■ Pressures lower than those listed indicate that the system
is undercharged.
■ Verify adjusted charge using the approach method.
5. Use the same digital thermometer to check liquid line
temperature.
6. Subtract the outdoor ambient temperature from the liquid line
temperature to determine the approach temperature.
_____ ° (Liquid Line Temperature °F) - _____ ° (Outdoor
Ambient Temperature °F) = _____ ° (Approach
Temperature °F)
7. Compare the approach value with those shown in the
Approach Values for Thermal Expansion Valve Systems chart.
■ If the approach values are too high, add refrigerant to
lower the approach temperature
■ If the approach values are too low, recover refrigerant
from the system to increase the approach temperature.
■ Approach value is the liquid line temperature minus the
outdoor ambient temperature (∆°F).
NOTE: For best results, use the same digital thermometer to
check both outdoor ambient and liquid temperatures.
Check Charge Using Normal Operating Pressures
Use the Normal Operating Pressures chart to perform
maintenance checks.
NOTES:
■ This chart is not a procedure for charging the system.
■ Minor variations in these pressures may be due to differences
in installations.
■ Significant deviations could mean that the system is not
properly charged or that a problem exists with some
component in the system.
Normal Operating Pressures
Sub-cooling Values
Model W4GH824A W4GH836A
Temperature ºF 7 7
Model W4GH848A W4GH860A
Temperature ºF 4 5
Approach Values for Thermal Expansion Valve Systems
Model W4GH824A W4GH836A
Temperature ºF 4 3
Model W4GH848A W4GH860A
Temperature ºF 7 7
W4GH824A W4GH836A W4GH848A W4GH860A
Air Temperature Entering
Outdoor Coil ºF (ºC) Liquid Suction Liquid Suction Liquid Suction Liquid Suction
Cooling
65 (18) 208 139 212 147 223 142 236 139
75 (23.9) 257 144 254 147 265 144 278 141
85 (29.4) 297 148 295 148 306 147 321 142
95 (35) 342 153 337 149 348 149 363 144
105 (40.6) 387 158 379 150 390 151 405 146
115 (46.1) 431 162 420 151 431 154 448 147
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