Lennox 13HPX Series Unit Information page 13

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 6. Using Weigh In Method
1. Check the airflow as illustrated in figure 4 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 tables, (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:
When the outdoor ambient temperature is 60°F (15°C) and
Using cooling mode
above. Target 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.
When the outdoor ambient temperature is below 60°F (15°C).
Using heating mode
Target subcooling 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 24 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 unit indoor matchup tables 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.
Figure 7. Using Subcooling Method
Page 13
1.. Check Liquid and suction line pressures
2.. Compare unit pressures with Normal
Operating Pressures tables.
3.. Conduct leak check; evacuate
previously outlined.
4.. Weigh in the unit nameplate charge plus
any charge required for
differences over feet.
This nameplate is for
purposes only. Go to actual nameplate
on outdoor unit for charge information.
as
line set
illustration