Lennox XC20-036-230-01 Installation And Service Procedure page 77

Use the WEIGH-IN method for adding initial refrigerant charge, and then use SUBCOOLING method for for verifying refrigerant charge.
WEIGH-IN
CHARGING METHOD
64ºF (17.7ºC) and Below
Adjust amount for variation in
line set length and liquid line
Amount specified
diameter using table below.
on nameplate
+
Liquid Line
Set Diameter
5/16"
3/8"
1/2"
SUBCOOLING
1. THE DIAGNOSTIC SCREEN ON THE THERMOSTAT OR OUTDOOR CONTROL 7-SEGMENT DISPLAY WILL SHOW INDOOR AND
OUTDOOR MOTOR CFMS OR RPMS.
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 THE APPLICABLE CHARGING STICKER, NORMAL OPERATING PRESSURES, HIGH STAGE.
NOTE
DIFFERENCES MAY MEAN IMPROPER CHARGE OR OTHER SYSTEM PROBLEM.
5. SET THERMOSTAT FOR HEAT/COOL DEMAND, DEPENDING ON MODE BEING USED:
USE
USING COOLING MODE
COOLING
MODE
SUBCOOLING VALUES (SECOND STAGE - HIGH CAPACITY) IN APPLICABLE CHARGING STICKER ARE BASED ON 70 TO
80°F (21-27°C) INDOOR RETURN AIR TEMPERATURE; IF NECESSARY, OPERATE HEATING TO REACH THAT
60ºF
TEMPERATURE RANGE; THEN SET THERMOSTAT TO COOLING MODE SETPOINT TO 68ºF (20ºC) WHICH SHOULD CALL
(15ºC)
FOR SECOND-STAGE (HIGH STAGE) COOLING. WHEN PRESSURES HAVE STABILIZED, CONTINUE WITH STEP 6.
USE
HEATING USING HEATING MODE
MODE
SUBCOOLING VALUES (SECOND-STAGE - HIGH CAPACITY) IN APPLICABLE CHARGING STICKER 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 THE APPLICABLE CHARGING STICKER AND RECORD IT IN THE SATº SPACE.
8. SUBTRACT LIQº TEMPERATURE FROM SATº TEMPERATURE TO DETERMINE SUBCOOLING; RECORD IT IN SCº SPACE.
SATº
9. COMPARE SCº RESULTS WITH APPLICABLE CHARGING STICKER, BEING SURE TO NOTE ANY ADDITIONAL CHARGE FOR
LINE SET AND/OR MATCH-UP.
LIQº –
10. IF SUBCOOLING VALUE IS GREATER THAN SHOWN IN APPLICABLE CHARGING STICKER FOR THE APPLICABLE UNIT,
SCº =
REMOVE REFRIGERANT; IF LESS THAN SHOWN, ADD REFRIGERANT.
11. IF REFRIGERANT IS ADDED OR REMOVED, REPEAT STEPS 6 THROUGH 10 TO VERIFY CHARGE.
12. DISCONNECT GAUGE SET AND RE-INSTALL BOTH THE LIQUID AND SUCTION SERVICE VALVE CAPS.
Figure 57. Using HFC-410A Subcooling Method - High Speed (High Capacity)
°F Psig °F Psig
32 100.8 48 137.1
33 102.9 49 139.6
34 105.0 50 142.2
35 107.1 51 144.8
36 109.2 52 147.4
37 111.4 53 150.1
38 113.6 54 152.8
39 115.8 55 155.5
40 118.0 56 158.2
41 120.3 57 161.0
42 122.6 58 163.9
43 125.0 59 166.7
44 127.3 60 169.6
45 129.7 61 172.6
46 132.2 62 175.4
47 134.6
Total charge
=
HFC-410A
(ounces per foot)
[(Line set oz./ft. x total length) ­ (factory charge for line set)] = charge adjustment
0.40 Example: Units are factory­charged for 15 feet (4.6 meters) of 3/8" line set.
Factory charge for 3/8" is 0.60 oz/ft x 15 = 9.0 ounces.
0.60
1.00
Figure 56. Using HFC-410A Weigh-In Method
CHARGING METHOD
-
THE REFERENCE TABLE IS A GENERAL GUIDE. EXPECT MINOR PRESSURE VARIATIONS. SIGNIFICANT
— WHEN THE OUTDOOR AMBIENT TEMPERATURE IS 60°F (15°C) AND ABOVE. TARGET
— WHEN THE OUTDOOR AMBIENT TEMPERATURE IS BELOW 60°F (15°C). TARGET
.
Table 19 HFC-410A Temperature (°F) - Pressure (Psig)
°F Psig °F Psig
63 178.5 79 231.6
64 181.6 80 235.3
65 184.3 81 239.0
66 187.7 82 242.7
67 190.9 83 246.5
68 194.1 84 250.3
69 197.3 85 254.1
70 200.6 86 258.0
71 203.9 87 262.0
72 207.2 88 266.0
73 210.6 89 270.0
74 214.0 90 274.1
75 217.4 91 278.2
76 220.9 92 282.3
77 224.4 93 286.5
78 228.0
NOTE - Insulate liquid line when it is routed through 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 - The nameplate is shown for illustration purposes only. Go to
actual nameplate on outdoor unit for charge information.
Charging Formula for Liquid Line Charge Adjustments
(All charging MUST be performed while system is operating
either at maximum speed or 100% demand.)
°F Psig °F
94 290.8 110
95 295.1 111
96 299.4 112
97 303.8 113
98 308.2 114
99 312.7 115
100 317.2 116
101 321.8 117
102 326.4 118
103 331.0 119
104 335.7 120
105 340.5 121
106 345.3 122
107 350.1 123
108 355.0 124
109 360.0
77
Psig °F Psig °F
365.0 141
125 445.9
370.0 126 451.8 142
375.1 127 457.6 143
380.2 128 463.5 144
385.4 129 469.5 145
390.7 130 475.6 146
396.0 131 481.6 147
401.3 132 487.8 148
406.7 133 494.0 149
412.2 134 500.2 150
417.7 135 506.5 151
423.2 136 512.9 152
428.8 137 519.3 153
434.5 138 525.8 154
440.2 139 532.4 155
140 539.0
Psig
545.6
552.3
559.1
565.9
572.8
579.8
586.8
593.8
601.0
608.1
615.4
622.7
630.1
637.5
645.0
XC20