Use WEIGH IN method for adding initial refrigerant charge, and then use SUBCOOLING method for for verifying refrigerant charge.
WEIGH IN CHARGING METHOD
CALCULATING SYSTEM CHARGE FOR OUTDOOR UNIT VOID OF CHARGE
If the system is void of refrigerant, first, locate and repair any leaks and then weigh in the refrigerant charge into the unit. To calculate the total refriger- ant charge:
Amount specified on | Adjust amount. for variation in line set | Additional charge specified per indoor | Total Charge | ||||||||||
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| Refrigerant Charge per Line Set Length |
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| LIQUID LINE SET DIAMETER | OUNCES PER 5 FEET (G PER 1.5 M) ADJUST FROM 15 FEET (4.6 M) |
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| LINE SET* |
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| 3/8" (9.5 MM) |
| 3 OUNCE PER 5’ (85 G PER 1.5 M) |
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*If line length is greater than 15 ft. (4.6 m), add this amount. If line length is less than 15 ft. (4.6 m), subtract this amount.
NOTEthrough areas where the surrounding ambient temperature could become higher than the temperature of the liquid line or when pressure drop is equal to or greater than 20 psig.
NOTE . Go to actual nameplate on outdoor unit for charge information.
Figure 21. Using HFC−410A Weigh In Method
SUBCOOLING CHARGING METHOD
SATº LIQº – SCº =
USE
COOLING
MODE
60ºF
(15ºC)
USE
HEATING
MODE
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 coolingmode 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 10, Normal Operating Pressures, High Stage.
NOTE
mean improper charge or other system problem.
5.Set thermostat for heat/cool demand, depending on mode being used:
USING COOLING MODE When the outdoor ambient temperature is 60°F (15°C) and above. Target subcooling values (second stage − high capacity) in table 10 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 to cooling mode setpoint to 68ºF (20ºC) which should call for second−stage (high stage) 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 10 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 to heating mode setpoint to 77ºF (25ºC) which should call for second−stage (high stage) heating. When pressures have stabilized, continue with Step 6.
6.Read the liquid line temperature; record in the LIQº space.
7.Read the liquid line pressure; then find its corresponding temperature in the temperature/ pressure chart listed in table 11 and record it in the SATº space.
8.Subtract LIQº temperature from SATº temperature to determine subcooling; record it in SCº space.
9.Compare SCº results with tables 4 through 9, being sure to note any additional charge for line set and/or match− up.
10.If subcooling value is greater than shown in tables 4 through 9 for the applicable unit, remove refrigerant; if less than shown, add refrigerant.
11.If refrigerant is added or removed, repeat steps 5 through 6 to verify charge.
12.Disconnect gauge set and re−install both the liquid and suction service valve caps.
Figure 22. Using HFC−410A Subcooling Method tage (High Capacity)
Page 29
XP17 SERIES