Lennox Dave Signature Collection XC15 Installation Instructions Manual page 18

START: Measure outdoor ambient temperature
USE WEIGH-IN METHOD DO NOT CHARGE UNIT
Weigh-in or remove refriger- (Results of charging at low
ant based upon line length temperatures not reliable)
If value is greater than shown (high
approach), add refrigerant; if less than
shown (liquid temp too close to ambient
temp, low approach),
refrigerant.
APPº (Approach) Values(F:+/−1.0° [C: +/−0.6°])
ºF (ºC)* −024
Any 8 (4.4)
*Temperature of air entering outdoor coil
START: Measure outdoor ambient temperature
USE WEIGH-IN METHOD
DO NOT CHARGE UNIT
Weigh-in or remove refrigerant
(Results of charging at low
based upon line length
temperatures not reliable)
If refrigerant added or
removed, verify charge using
the approach method
If value is greater than shown,
remove refrigerant; if less than
shown, add refrigerant
SCº (Subcooling) Values (F:+/−1.0° [C: +/−0.6°])
ºF (ºC)* −024
Any 7 (3.9.)
*Temperature of air entering outdoor coil
506044−01 06/08
Outdoor
Ambient 65ºF
(18ºC)?
BELOW
If refrigerant added or removed,
retest to confirm that unit is
properly charged
remove
Models
−030 −036 −042 . . .
13 (7.2) 13 (7.2) 15 (8.3)
Figure 34. Using Approach TXV Method
Outdoor
Ambient 65ºF
(18ºC)?
BELOW
BLOCK OUTDOOR COIL: [sometimes necessary with
lower temperatures] Use cardboard or plastic sheet to
restrict the airflow through the outdoor coil to achieve
pressures from 325−375 psig (2240−2585 kPa). Higher
pressures are needed to check charge. Block equal
sections of air intake panels and move coverings sideways
until the liquid pressure is in the above noted ranges.
Models
−030 −036 −042
4 (2.2) 5 (2.8) 7 (3.9)
Figure 35. Using Subcooling TXV Method
ABOVE
−048 . . . −060
. 6 (3.3) . 10 (5.6)
ABOVE
. . . −048 . . . −060
. 6 (3.3) . . 7 (3.9)
Page 18
1. Confirm proper airflow across coil using figure
31.
2. Compare unit pressures with Table 5, Normal
Operating Pressures.
3. Use APPROACH to correctly charge unit or to
verify the charge is correct.
4. Set thermostat to call for heat (must have a
cooling load between 70-80ºF (21−26ºC).
5. Connect gauge set.
6. When heat demand is satisfied, set thermostat
to call for cooling.
7. Allow temperatures and pressures to stabilize.
8. Record outdoor ambient temperature:
AMBº =_________
9. Record line temp:
LIQº = __________
10. Subtract to determine approach (APPº):
LIQº_____ − AMBº _____ = APPº_____
11. Compare results with table to the left.
1. Confirm proper airflow across coil using figure
31.
2. Compare unit pressures with Table 5, Normal
Operating Pressures.
3. Use SUBCOOLING to correctly charge unit or to
verify the charge is correct.
4. Set thermostat to call for heat (must have a
cooling load between 70-80ºF (21−26ºC)
5. Connect gauge set
6. Measure outdoor ambient temperature
7. When heat demand is satisfied, set thermostat to
call for cooling
8. Allow temperatures and pressures to stabilize.
NOTE − If necessary, block outdoor coil to
maintain 325 − 375 psig.
9. Record liquid line temp:
LIQº = ______
10. Measure liquid line pressure and use the value to
determine saturation temperature (see table 4):
SATº = ______
11. Subtract to determine subcooling (SCº):
SATº_____ − LIQº _____ = SCº _____
12. Compare results with table to the left.