Lennox XP14-018-230-06 Nstallation And Service Instructions page 29

WEIGH IN
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
nameplate
SUBCOOLING
USE COOLING
MODE
60ºF (15º)
USE HEATING
MODE
SATº
LIQº –
SCº =
CHARGING METHOD
Adjust amount. for variation in line set
length listed on line set length table below.
+
Refrigerant Charge per Line Set Length
LIQUID LINE SET DIAMETER
3/8" (9.5 MM)
*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.
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 above nameplate is for illustration purposes only. Go to actual nameplate on outdoor unit for charge
information.
Figure 17. Using HFC-410A Weigh In Method
1 Check the airflow as illustrated in figure 16 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 tables are 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
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 9 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 match up tables being sure to note any additional charge for line set and/or match-up.
10 If subcooling value is greater than shown in the match up 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.
12 Disconnect gauge set and re-install both the liquid and suction service valve caps.
Figure 18. Using Subcooling Method
Additional charge specified per indoor
unit match-ups starting on pages 29
+
OUNCES PER 5 FEET (G PER 1.5 M) ADJUST FROM 15 FEET (4.6 M)
3 OUNCE PER 5' (85 G PER 1.5 M)
—When the outdoor ambient temperature is 60°F (15°C) and above. Target subcooling
—When the outdoor ambient temperature is below 60°F (15°C). Target subcooling
Page 29
and 30.
=
LINE SET*
Total Charge
XP14 SERIES