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XPG20 SERIES
1. Check the airflow as illustrated in Figure 20 to be sure the indoor airflow is as
required. (Make any air flow adjustments before continuing with the following
procedure.)
2. Measure outdoor ambient temperature; determine whether to use
cooling
mode
or
heating mode
to check charge.
3. Connect gauge set.
4. Check liquid and vapor line pressures. Compare pressures with either heat or
cooling mode normal operating pressures in Table 3 (second stage − high capacity),
NOTE The reference table is a general guide. Expect minor pressure variations.
Significant differences may mean improper charge or other system problem.
5. Set thermostat for heat/cool demand, depending on mode being used:
USE
COOLING
MODE
USE
HEATING
MODE
60ºF
(15º)
SATº
LIQº
–
SCº
=
SUBCOOLING
6. Read the liquid line temperature; record in the LIQº space.
7. Read the liquid line pressure; then find its corresponding temperature in the tem-
perature/ pressure chart listed in Table 5 and record it in the SATº space.
8. Subtract LIQº temperature from SATº temperature to determine subcooling; re-
cord it in SCº space.
9. Compare SCº results with Table 4, being sure to note any additional charge for
line set and/or match−up.
10. If subcooling value is greater than shown in Table 4 for the applicable unit, remove
refrigerant; if less than shown, add refrigerant.
11. If refrigerant is added or removed, repeat steps 4 through 5 to verify charge.
12. Disconnect gauge set and re−install both the liquid and suction service valve caps.
USING COOLING MODE
When the outdoor ambient temperature is 60°F (15°C)
and above. Target subcooling values (second−stage − high capacity) in Table 3 are
based on 70 to 80°F (21−27°C) indoor return air temperature; if necessary, operate
heating to reach that temperature range; then set thermostat cooling mode
setpoint to 68ºF (20ºC) which should call for second−stage (high capacity) cooling.
When pressures have stabilized, continue with step 6.
USING HEATING MODE
When the outdoor ambient temperature is below 60°F
(15°C). Target subcooling values (second−stage − high capacity) in Table 3 are
based on 65−75°F (18−24°C) indoor return air temperature; if necessary, operate
cooling to reach that temperature range; then set thermostat heating mode
setpoint to 77ºF (25ºC) which should call for second−stage (high capacity) heating.
When pressures have stabilized, continue with step 6.
Figure 22. Using HFC−410A Subcooling Method Second Stage (High Capacity)
