Page 18
506109−01 10/08
WEIGH IN TXV
START: Measure outdoor ambient temperature
1. Check Liquid and suction line pressures
2. Compare unit pressures with Table 5,
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 15 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
64ºF
(17.7ºC) and
BELOW
65ºF
(18ºC) and
ABOVE
Figure 34. HCFC−22 Weigh In TXV Method
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 200−250 psig
(1379−1724 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
32.
2. Compare unit pressures with Table 5,
Normal
Operating Pressures
.
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 4):
SATº = ______
10. Subtract to determine subcooling (SCº):
SATº_____ − LIQº _____ = SCº _____
11. Compare results with table below.
Figure 35. HCFC−22 Subcooling TXV Charge
MORE
or
LESS
If value is
LESS
than shown, add
refrigerant.
If refrigerant is added
or removed, verify
charge using the
Approach Method
.
64ºF
(17.7ºC) and
BELOW
65ºF
(18ºC)
and
ABOVE
ABOVE or
BELOW
−018
−024
−030
−036
−042
−048
−060
TEMP*
7 (3.8)
12 (6.7)
9 (5.0)
10 (5.6)
14(8.0)
10 (5.6)
13 (7.2)
*Temperature of air entering outdoor coil is 65ºF (18ºC) or above.
