Lennox Elite Series XP13 Units Installation Instructions Manual page 19

WEIGH IN
Refrigerant Charge per Line Set Length
Ounces per 5 feet (g per 1.5 m)
Liquid Line
adjust from 15 feet (4.6 m) line set*
Set Diameter
3/8" (9.5 mm)
3 ounce per 5' (85 g per 1.5 m)
NOTE − *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.
SUBCOOLING
USE COOLING
MODE
60ºF (15º)
USE HEATING
MODE
SATº
LIQº –
SCº =
Figure 33. Using Weigh In Method
1 Check the airflow as illustrated in figure 32 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 Normal Operating Pressures table 4,
(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:
Using cooling mode
subcooling values in table below 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). When pressures have stabilized, continue with step 6.
Using heating mode
values in table below 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). 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 5 and record it in the SATº space.
8 Subtract LIQº temp. from SATº temp. to determine subcooling; record it in SCº space.
9 Compare SCº results with table below, being sure to note any additional charge for line set and/or match−up.
10 If subcooling value is greater than shown in table 3 for the applicable unit, 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 34. Using Subcooling Method
Page 19
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 subcooling
1. Check Liquid and suction line pressures
2. Compare unit pressures with Table 4,
Normal Operating Pressures.
3. Conduct leak check;
previously outlined.
4. Weigh in the unit nameplate charge plus
any charge required for line set differences
over feet.
This nameplate is for illustration purposes
only. Go to actual nameplate on outdoor
unit for charge information.
evacuate as
XP13 SERIES