Lennox Merit Series 13ACX Installation Instructions Manual page 18

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)
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.
If refrigerant is added
or removed, verify
charge using the
Approach Method.
If value is LESS
than shown, add
refrigerant.
START: Measure outdoor ambient temperature
USE SUPERHEAT
WEIGH IN RFC
Refrigerant Charge per Line Set Length
Liquid Line Ounces per 5 feet (g per 1.5 m)
Set Diameter adjust from 15 feet (4.6 m) line set*
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.
506081−01 09/08
ABOVE or
BELOW
64ºF and
BELOW
If value is MORE
than shown, remove
refrigerant.
ºF (ºC)*
Any
MORE or
*Temperature of air entering outdoor coil
LESS
Figure 33. HFC−410A Subcooling TXV Charge
ABOVE or
BELOW
40ºF
and
ABOVE
Figure 34. HFC−410A Weigh In RFC Method
Page 18
1. Confirm proper airflow across coil using figure
29.
65ºF
2. Compare unit pressures with Table 4, Normal
and
Operating Pressures.
ABOVE
3. Set thermostat to call for heat (must have a
cooling load between 70-80ºF (21−26ºC)
4. Connect gauge set
5. Measure outdoor ambient temperature
6. When heat demand is satisfied, set thermostat to
call for cooling
7. Allow temperatures and pressures to stabilize.
NOTE − If necessary, block outdoor coil to
maintain 325 − 375 psig.
8. Record liquid line temperature:
LIQº = ______
9. Measure liquid line pressure and use the value to
determine saturation temperature (see table 5):
SATº = ______
10. Subtract to determine subcooling (SCº):
SATº_____ − LIQº _____ = SCº _____
11. Compare results with table below.
SCº (Subcooling) Values (F:+/−1.0° [C: +/−0.6°])
−018 −024 −030
10 (5.6) 10 (5.6) 9 (5.0)
39ºF and
BELOW
−036 −042 −048
12 (6.7) 9 (5.0) 9 (5.0)
1. Check Liquid and suction line pressures
2. Compare unit pressures with Table 4,
Normal Operating Pressures.
3. Conduct leak check; evacuate
previously outlined.
4. Weigh in the unit nameplate charge plus
any charge required for line set differences
over feet.
This nameplate is for illustration purposes
only. Go to actual nameplate on outdoor unit
for charge information.
−060
7 (3.9)
as