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
