Using Hfc-410A Weigh In Method; Using Hfc-410A Subcooling Method — High Speed (High Capacity) - Lennox XP25-024-230-01 Installation And Service Procedure

WEIGH-IN
Use method for adding initial refrigerant charge, then use
refrigerant charge.
WEIGH-IN
CHARGING METHOD FOR LONG LINE SETS
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
CHARGING METHOD
1.
2.
3.
4.
USE
COOLING
MODE
60ºF 5.
(15ºC)
USE
HEATING
MODE
SATº
LIQº –
6.
SCº =
7.
8.
9.
10.
11.
12.
Figure 66. Using HFC-410A Subcooling Method — High Speed (High Capacity)
Total charge
=
HFC-410A
[(Line set oz./ft. x total length) ­ (factory charge for line set)] = charge adjustment
(ounces per foot)
0.40
0.60
1.00
Figure 65. Using HFC-410A Weigh In Method
(All charging MUST be performed while system is operating either at maximum speed or 100% demand.)
THE DIAGNOSTIC SCREEN ON THE THERMOSTAT OR OUTDOOR CONTROL 7-SEGMENT DISPLAY WILL SHOW
INDOOR AND OUTDOOR MOTOR CFMS OR RPMS.
MEASURE OUTDOOR AMBIENT TEMPERATURE; DETERMINE WHETHER TO USE COOLING MODE OR HEATING MODE
TO CHECK CHARGE.
CONNECT GAUGE SET.
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 - THE REFERENCE TABLE IS A GENERAL GUIDE. EXPECT MINOR PRESSURE VARIATIONS. SIGNIFICANT
DIFFERENCES MAY MEAN IMPROPER CHARGE OR OTHER SYSTEM PROBLEM.
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 APPLICABLE CHARGING STICKER 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 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.
READ THE LIQUID LINE TEMPERATURE; RECORD IN THE LIQº SPACE.
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.
SUBTRACT LIQº TEMPERATURE FROM SATº TEMPERATURE TO DETERMINE SUBCOOLING; RECORD IT IN SCº
SPACE.
COMPARE SCº RESULTS WITH APPLICABLE CHARGING STICKER, BEING SURE TO NOTE ANY ADDITIONAL
CHARGE FOR LINE SET AND/OR MATCH-UP.
IF SUBCOOLING VALUE IS GREATER THAN SHOWN IN APPLICABLE CHARGING STICKER FOR THE APPLICABLE
UNIT, REMOVE REFRIGERANT; IF LESS THAN SHOWN, ADD REFRIGERANT.
IF REFRIGERANT IS ADDED OR REMOVED, REPEAT STEPS 6 THROUGH 10 TO VERIFY CHARGE.
DISCONNECT GAUGE SET AND RE-INSTALL BOTH THE LIQUID AND SUCTION SERVICE VALVE CAPS.
SUBCOOLING
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 shown for illustration purposes
only. Go to actual nameplate on outdoor unit for charge information.
Charging Formula for Liquid Line Charge Adjustments
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.
Page 87
method for for verifying
XP25