Lennox Signature XP21 Series Installation And Service Procedure page 28

WEIGH IN
Use method for adding initial refrigerant charge, and then use
fying refrigerant charge.
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 REFRIGERANT CHARGE:
AMOUNT SPECIFIED
ON NAMEPLATE
SUBCOOLING
1. CHECK THE AIRFLOW AS ILLUSTRATED IN FIGURE 16 TO BE SURE THE INDOOR AIRFLOW IS AS REQUIRED. (MAKE
2. MEASURE OUTDOOR AMBIENT TEMPERATURE; DETERMINE WHETHER TO USE COOLING MODE OR HEATING MODE
3. CONNECT GAUGE SET.
USE
4. CHECK LIQUID AND VAPOR LINE PRESSURES. COMPARE PRESSURES WITH EITHER HEAT OR COOLING MODE
COOLING
MODE
60ºF
(15ºC)
USE
5. SET THERMOSTAT FOR HEAT/COOL DEMAND, DEPENDING ON MODE BEING USED:
HEATING
MODE
SATº
LIQº –
6. READ THE LIQUID LINE TEMPERATURE; RECORD IN THE LIQº SPACE.
SCº =
7. READ THE LIQUID LINE PRESSURE; THEN FIND ITS CORRESPONDING TEMPERATURE IN THE TEMPERATURE/
8. SUBTRACT LIQº TEMPERATURE FROM SATº TEMPERATURE TO DETERMINE SUBCOOLING; RECORD IT IN SCº
9. COMPARE SCº RESULTS WITH TABLES 3 THROUGH 7, BEING SURE TO NOTE ANY ADDITIONAL CHARGE FOR LINE
10. IF SUBCOOLING VALUE IS GREATER THAN SHOWN IN TABLES 3 THROUGH 7 FOR THE APPLICABLE UNIT, REMOVE
11. IF REFRIGERANT IS ADDED OR REMOVED, REPEAT STEPS 5 THROUGH 6 TO VERIFY CHARGE.
12. DISCONNECT GAUGE SET AND RE−INSTALL BOTH THE LIQUID AND SUCTION SERVICE VALVE CAPS.
Figure 18. Using HFC−410A Subcooling Method
XP21
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
CHARGING METHOD
ANY AIR FLOW ADJUSTMENTS BEFORE CONTINUING WITH THE FOLLOWING PROCEDURE.)
TO CHECK CHARGE.
NORMAL OPERATING PRESSURES IN TABLE 8, 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.
USING COOLING MODE
SUBCOOLING VALUES (SECOND STAGE − HIGH CAPACITY) IN TABLE 8 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
SUBCOOLING VALUES (SECOND−STAGE − HIGH CAPACITY) IN TABLE 8 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.
PRESSURE CHART LISTED IN TABLE 9 AND RECORD IT IN THE SATº SPACE.
SPACE.
SET AND/OR MATCH−UP.
REFRIGERANT; IF LESS THAN SHOWN, ADD REFRIGERANT.
ADDITIONAL CHARGE SPECIFIED
PER INDOOR UNIT MATCH−UPS
STARTING ON PAGE 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
WHEN THE OUTDOOR AMBIENT TEMPERATURE IS BELOW 60°F (15°C). TARGET
High Stage (High Capacity)
Page 28
SUBCOOLING
method for for veri-
=
LINE SET*
TOTAL
CHARGE