Page 18
506101−01 07/09
START: Measure outdoor ambient temperature
64ºF and
BELOW
1. Check Liquid and suction line pressures
2. Compare unit pressures with Table 2,
Normal Operating Pressures.
3. Conduct leak check; evacuate as
previously outlined.
4. Weigh in the unit nameplate charge plus
any charge required for line set differences
over feet.
Liquid Line
Set Diameter
Ounces per 5 feet (g per 1.5 m)
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.
Refrigerant Charge per Line Set Length
USE EITHER APPROACH
OR SUBCOOLING
METHOD
This nameplate is for illustration purposes
only. Go to actual nameplate on outdoor
unit for charge information.
ABOVE or
BELOW
WEIGH IN TXV
Figure 30. Weigh In Method
65ºF
and
ABOVE
DO NOT CHARGE UNIT
(Results of charging at low
temperatures not reliable)
START: Measure outdoor ambient temperature
USE WEIGH-IN METHOD
Weigh-in or remove refrigerant
based upon line length
SCº (Subcooling) Values (F:+/−1.0° [C: +/−0.6°])
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 value is MORE
than shown, remove
refrigerant.
1. Confirm proper airflow across coil using figure
28.
2. Compare unit pressures with Table 2, Normal
Operating Pressures − Second Stage (High
Capacity).
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 second stage (high capacity) 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 3):
SATº = ______
10. Subtract to determine subcooling (SCº):
SATº_____ − LIQº _____ = SCº _____
11. Compare results with table below.
Figure 31. Subcooling TXV Charge Second Stage (High Capacity)
MORE or
LESS
If value is LESS
than shown, add
refrigerant.
If refrigerant is added
or removed, verify
charge using the
Approach Method.
64ºF and
BELOW
65ºF
and
ABOVE
ABOVE or
BELOW
Models
ºF (ºC)* −024 −036 −048 −060
Any 5 (2.7) 6 (3.3) 6 (3.3) 9 (5.0)
*Temperature of air entering outdoor coil
Second Stage (High Capacity)
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